Patent Application
20100135903
The present invention relates generally to a method of treating a neoplastic condition and to agents useful for same. More particularly, the present invention is directed to a method of facilitating the treatment of a metastatic neoplastic tumour in a localised manner by effecting the exposure of neoplastic cell intra-cellular molecules, preferably intra-nuclear molecules, suitable for use as a therapeutic target. The co-localisation of tumour cells and metastases to discrete tissue locations thereby renders the method of the present invention useful in terms of the delivery of bystander-based therapy.
Bibliographic details of the publications referred to by author in this specification are collected alphabetically at the end of the description.
The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.
Malignant tumours, or cancers, grow in an uncontrolled manner, invade normal tissues, and often metastasize and grow at sites distant from the tissue of origin. In general, cancers are derived from one or only a few normal cells that have undergone a poorly understood process called malignant transformation. Cancers can arise from almost any tissue in the body. Those derived from epithelial cells, called carcinomas, are the most common kinds of cancers. Sarcomas are malignant tumours of mesenchymal tissues, arising from cells such as fibroblasts, muscle cells, and fat cells. Solid malignant tumours of lymphoid tissues are called lymphomas, and marrow and blood-borne malignant tumours of lymphocytes and other hematopoietic cells are called leukemias.
Cancer is one of the three leading causes of death in industrialised nations. As treatments for infectious diseases and the prevention of cardiovascular disease continues to improve, and the average life expectancy increases, cancer is likely to become the most common fatal disease in these countries. Therefore, successfully treating cancer requires that all the malignant cells be removed or destroyed without killing the patient. An ideal way to achieve this would be to induce an immune response against the tumour that would discriminate between the cells of the tumour and their normal cellular counterparts. However, immunological approaches to the treatment of cancer have been attempted for over a century with unsustainable results.
Accordingly, current methods of treating cancer continue to follow the long used protocol of surgical excision (if possible) followed by radiotherapy and/or chemotherapy, if necessary. The success rate of this rather crude form of treatment is extremely variable but generally decreases significantly as the tumour becomes more advanced and metastasises. Further, these treatments are associated with severe side effects including disfigurement and scarring from surgery (e.g. mastectomy or limb amputation), severe nausea and vomiting from chemotherapy, and most significantly, the damage to normal tissues such as the hair follicles, gut and bone marrow which is induced as a result of the relatively non-specific targeting mechanism of the toxic drugs which form part of most cancer treatments.
Solid tumours cause the greatest number of deaths from cancer and mainly comprise tumours of the linings of the bronchial tree and the alimentary tract that are known as carcinomas. In the year 2000 in Australia, cancer accounted for 30% of male deaths and 25% of female deaths (Cancer in Australia 2000, 2003) and it accounted for 24% of male and 22% of female deaths in the US in year 2001 (Arias et al. 2003, National Vital Statistics Reports 52: 111-115). Solid tumours are not usually curable once they have spread or ‘metastasised’ throughout the body. The prognosis of metastatic solid tumours has improved only marginally in the last 50 years. The best chance for the cure of a solid tumour remains in the use of local treatments such as surgery and/or radiotherapy when the solid tumour is localised to its originating lining and has not spread either to the lymph nodes that drain the tumour or elsewhere. Nonetheless, even at this early stage, and particularly if the tumour has spread to the draining lymph nodes, microscopic deposits of cancer known as micrometastases may have already spread throughout the body and will subsequently lead to the death of the patient. In this sense, cancer is a systemic disease that requires systemically administered treatments. Of the patients who receive surgery and/or radiotherapy as definitive local treatment for their primary tumour and who have micrometastases, a minor proportion may be cured or at least achieve a durable remission from cancer by the addition of adjuvant systemic treatments such as cytotoxic chemotherapy or hormones.
Conventionally, solid cancer has been treated locally with surgery and/or radiotherapy, and during its metastatic stage with systemically administered cytotoxic drugs, which often interfere with the cell cycle of both normal and malignant cells. The relative selectivity of this approach for the treatment of malignant tissues is based to some extent on the more rapid recovery of normal tissues from cytotoxic drug damage. More recently, the targeted therapy of cancer has aimed to improve the therapeutic ratio of cancer treatment by enhancing its specificity and/or precision of delivery to malignant tissues while minimising adverse consequences to normal non-malignant tissues. Two of the major classes of targeted therapy are (i) the small molecule inhibitors such as the tyrosine kinase inhibitors imatinib mesylate (Glivec®), gefitinib (Iressa®) and erlotinib (Tarceva®), and (ii) the monoclonal antibodies (mAb) such as rituximab (Mabthera®) and trastuzumab (Herceptin®).
In parallel to the development of targeted therapies, combining at least two conventional anti-cancer treatments such as chemotherapy and radiotherapy in novel ways has been another approach to the development of cancer therapeutics. By exploiting synergistic interactions between the different modalities of treatment, combined modality treatment seeks to improve treatment efficacy so that the therapeutic ratio for the combined treatment is superior to that for each of the individual treatments.
Combined modality treatment using external beam radiation and radiosensitising chemotherapeutic drugs such as 5-fluorouracil and cisplatin (chemoradiotherapy) has improved survival in a number of solid tumours such as those of head and neck, lung, oesophagus, stomach, pancreas and rectum because of both improved local tumour control and reduced rates of distant failure (TS Lawrence. Oncology (Huntington) 17, 23-28, 2003). Although radiosensitising drugs increase tumour response, they also increase toxicity to adjacent normal tissues, which is especially true of the potent new generation radiosensitisers, gemcitabine and docetaxel. However, decreasing the radiation volume allows cytotoxic doses of gemcitabine to be better tolerated clinically (Lawrence T S. Oncology (Huntington) 17, 23-28, 2003). Chemoradiotherapy may overcome mutually reinforcing resistance mechanisms, which may only manifest in vivo.
Radioimmunotherapy (RIT) is a systemic treatment that takes advantage of the specificity and avidity of the antigen-antibody interaction to deliver lethal doses of radiation to cells that bear the target antigen. Radio-isotopes that emit β-particles (e.g. 131Iodine, 90Yttrium, 188Rhenium, and 67Copper) are usually used to label monoclonal antibodies (mAb) for therapeutic applications. The energy from β-radiation is released at relatively low intensity over distances measured in millimeters (Waldmann, Science 252: 1657-1662, 1991; Bender et al., Cancer Research 52: 121-126, 1992; O'Donoghue et al. Journal of Nuclear Medicine 36: 1902-1909, 1995; Griffiths et al. International Journal of Cancer 81: 985-992, 1999). Thus, high-energy β-emitters such as 90Yttrium are useful for the treatment of larger and heterogeneous solid tumours (Liu et al. Bioconjugate Chemistry 12:7-34, 2001). Research interest in radioimmunotherapy has been reawakened because in spite of the low radiation doses delivered, significant and unexpected biological effects of RIT upon surrounding host cells have been observed (Xue et al. Proceedings of the National Academy of Sciences of the United States of America 99: 13765-13770, 2002). Furthermore, the lower but biologically effective dose of radiation delivered by RIT had greater cytocidal effects than a larger dose of radiation conveyed as external beam radiotherapy (Dadachova et al. Proceedings of the National Academy of Sciences of the United States of America 101: 14865-14870, 2004). Nonetheless, the efficiency of RIT as a treatment for solid tumours may be hampered by the low penetration of antibody through the tissue barriers that surround the target antigen in the tumour, which will consequently extend circulatory half life of the antibody (Britz-Cunningham et al. Journal of Nuclear Medicine 44: 1945-1961, 2003). Furthermore, RIT is often impeded by the heterogeneity of the target antigen's expression within the tumour. Thus, although RIT affords molecular targeting of tumour cells, the major limitation of RIT remains the toxicity that may result from large doses of radiation that are delivered systemically in order to achieve sufficient targeting (Britz-Cunningham et al. 2003, supra; Christiansen et al. Molecular Cancer Therapy 3: 1493-1501, 2004). Altogether, a useful therapeutic index using RIT has proven difficult to achieve clinically (Sellers et al. Journal of Clinical Investigation 104: 1655-1661, 1999).
Tumour associated antigens, which would allow differential targeting of tumours while sparing normal cells, have also been the focus of cancer research. Although abundant ubiquitous antigens may provide a more concentrated and accessible target for RIT, studies adopting this have been extremely limited.
Accordingly, there is an urgent and ongoing need to develop improved systemic therapies for solid cancers, in particular metastatic cancers.
In work leading up to the present invention it has been determined that the induction of neoplastic cell death using a DNA damaging agent, such as a cytotoxic agent, results in the exposure of intracellular, in particular intranuclear, molecules which were not previously exposed to the extracellular environment. Still further, the levels of some of these molecules are actively increased as a result of one or both of the initial neoplastic transformation of the cell and delivery of the cytotoxic cell death signal. When considered in light of the fact that the induction of neoplastic cell death by this method generally takes longer than the induction of normal cell death, the exposure of these nuclear molecules by this method provides a means for generating a target to which a further more concentrated cell death effector mechanism can be more selectively delivered. Since the neoplastic cells which have initially undergone cell death to expose the target nuclear molecules are located proximally to neoplastic cells which remain viable, the application of a targeted second step cell death effector mechanism will induce the death of proximally located viable neoplastic cells. The two step method of the invention therefore enables the initial delivery of a lower dose systemic cytotoxin since the objective is not to attempt to kill all neoplastic cells, but merely to kill a subpopulation of these cells and thereby provide a target to which a more concentrated cell death effector mechanism can be subsequently directed. By reducing the concentration and overall volume of cytotoxin, which usually non-specifically targets a broad range of normal and neoplastic cells, the method of the present invention provides a means of delivering a highly effective second step treatment regime in a more localised manner, thereby reducing unwanted side effects. By preferably targeting nuclear molecules which have been actively increased subsequently to the exposure of a neoplastic cell to a DNA damaging agent provides a means of still further minimising the incidence of the induction of normal tissue cell death due to the localisation of significant concentrations of the second step effector mechanism to normal cells which have undergone cell death. Accordingly, the method of the present invention provides a means for improving the localised delivery of concentrated doses of treatment to a tumour and its metastases in a manner which is characterised by significantly improved outcomes and/or reduced side effects relative to those which would normally be expected in the context of the conventional treatment of an equivalent type of tumour. This is an extremely significant development since current protocols directed to treating metastatic disease are based on the non-targeted systemic delivery of chemotherapeutic agents.
Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.
As used herein, the term “derived from” shall be taken to indicate that a particular integer or group of integers has originated from the species specified, but has not necessarily been obtained directly from the specified source. Further, as used herein the singular forms of “a”, “and” and “the” include plural referents unless the context clearly dictates otherwise.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
One aspect of the present invention provides a method for the localisation treatment of a neoplastic condition in a subject, said method comprising:
In another aspect the present invention provides a method for the localised treatment of a malignant neoplastic condition in a subject, said method comprising:
In yet another aspect there is provided a method for the localised treatment of a metastatic neoplastic condition in a subject, said method comprising:
In still another aspect there is provided a method for the localised treatment of a metastatic neoplastic condition in a subject, said method comprising:
In yet still another aspect there is provided a method for the localised treatment of a metastatic neoplastic condition in a subject, said method comprising:
In still yet another aspect there is provided a method for the localised treatment of a metastatic neoplastic condition in a subject, said method comprising:
In a further aspect there is provided a method for the localised treatment of a metastatic neoplastic condition in a subject, said method comprising:
In another further aspect there is provided a method for the localised treatment of a metastatic neoplastic tumour in a subject, said method comprising:
Another aspect of the present invention is directed to the use of:
In yet another further aspect, the present invention contemplates a pharmaceutical composition comprising the agents as hereinbefore defined together with one or more pharmaceutically acceptable carriers and/or diluents.
and 72 h ▪) for sulforhodamine 101 staining. Inset summarizes the dependence of the protein cross-linking ratio on MDC concentration at 48 h (—) and 72 h ( . . . ) after cisplatin treatment of Jurkat cells. (E) Jurkat cells incubated with cisplatin in the absence or presence of increasing concentrations of MDC were stained with 3B9. 3B9-specific binding is presented as Net MFI±SEM (n=3). Inset summarizes the dependence of 3B9-specific binding on MDC concentration at 24 h (—), 48 h (— —) and 72 h ( . . . ) after cisplatin treatment of Jurkat cells. Data are representative of three identical and independent assays, which produced similar results.
and the labelling of both heavy and light chains.
The present invention is predicated, in part, on the determination that intra-cellular molecules, in particular intra-nuclear molecules, which are exposed to the extracellular environment as a result of DNA damaging treatment regimes provide a suitable target to enable a more localised second step neoplastic treatment regime. Still further, the use of molecules which are overexpressed in malignant cells and/or, as determined in the context of the development of the present invention, the level of which are increased due to the first step exposure to a DNA damaging agent provides a highly valuable and effective means of effecting the preferential delivery of a second step treatment to populations of neoplastic cells, thereby minimising the inadvertent exposure of normal cells. This is a significant difference to the notion of merely binding pre-existing dead neoplastic cells in which the levels of the subject nuclear molecule are unlikely to have been increased unless said death was induced via a cell damage mechanism and/or dissipation or clearance of the dead cell components has not occurred. The selectivity of this method can be rendered still more pronounced by designing the timing of the two-step treatment regimen to take advantage of the fact that the induction of normal cell death, and thereby the clearance of these cells, occurs more quickly than the induction of neoplastic cell death. Accordingly, the timing of the delivery of the second step treatment can be designed to occur at a point at which the proportion of any collaterally induced normal dead cells is at their lowest point. Since the objective of the first step treatment is merely to kill or to sensitise for killing (i.e. lower the threshold for killing) a subpopulation of neoplastic cells sufficient to provide a suitable target to enable the targeted delivery of a more toxic second step treatment, the method of the invention conveniently enables the delivery of lower concentrations of first step systemic treatments, thereby minimising unwanted side effects, prior to the delivery of a localised higher dose second step treatment. Again, the reduction in the concentration of the non-targeted first step treatment also contributes to reducing the side effects which would be apparent in the context of conventional systemic cytotoxic treatment regimes where this treatment step would be delivered at a much higher dose and, further, often in the context of multiple repeated rounds over a period of months. This development now provides a realistic means of moving away from the treatment of metastatic disease via the non-targeted, systemic delivery of chemotherapy.
Accordingly, one aspect of the present invention provides a method for the treatment of a neoplastic condition in a subject, said method comprising:
Reference to “localised” treatment hereafter should be understood as a reference to treatment which is focussed on the sites of neoplastic cells, as opposed to acting on non-neoplastic tissue. However, it should be appreciated that the method of the present invention is designed to effect an increased incidence of localised treatment but may not necessarily entirely eliminate the incidence of neoplastic tissue effects although this is usefully reduced.
Reference to a “neoplastic condition” should be understood as a reference to a condition characterised by the presence of development of encapsulated or unencapsulated growths or aggregates of neoplastic cells. Reference to a “neoplastic cell” should be understood as a reference to a cell exhibiting abnormal growth. The term “growth” should be understood in its broadest sense and includes reference to enlargement of neoplastic cell size as well as proliferation.
The phrase “abnormal growth” in this context is intended as a reference to cell growth which, relative to normal cell growth, exhibits one or more of an increase in individual cell size and nuclear/cytoplasmic ratio, an increase in the rate of cell division, an increase in the number of cell divisions, a decrease in the length of the period of cell division, an increase in the frequency of periods of cell division or uncontrolled proliferation and evasion of apoptosis. Without limiting the present invention in any way, the common medical meaning of the term “neoplasia” refers to “new cell growth” that results as a loss of responsiveness to normal growth controls, eg. to neoplastic cell growth. Neoplasias include “tumours” which may be benign, pre-malignant or malignant. The term “neoplasm” should be understood as a reference to a lesion, tumour or other encapsulated or unencapsulated mass or other form of growth or cellular aggregate which comprises neoplastic cells.
The term “neoplasm”, in the context of the present invention should be understood to include reference to all types of cancerous growths or oncogenic processes, metastatic tissues or malignantly transformed cells, tissues or organs irrespective of histopathologic type or state of invasiveness.
The term “carcinoma” is recognised by those skilled in the art and refers to malignancies of epithelial or endocrine tissues including respiratory system carcinomas, gastrointestinal system carcinomas, genitourinary system carcinomas, testicular carcinomas, breast carcinomas, prostate carcinomas, endocrine system carcinomas and melanomas. Exemplary carcinomas include those forming from tissue of the breast. The term also includes carcinosarcomas, e.g. which include malignant tumours composed of carcinomatous and sarcomatous tissues. An “adenocarcinoma” refers to a carcinoma derived from glandular tissue or in which the tumour cells form recognisable glandular structures.
The neoplastic cells comprising the neoplasm may be any cell type, derived from any tissue, such as an epithelial or non-epithelial cell. Reference to the terms “malignant neoplasm” and “cancer” and “carcinoma” herein should be understood as interchangeable.
The term “neoplasm” should be understood as a reference to a lesion, tumour or other encapsulated or unencapsulated mass or other form of growth or cellular aggregate which comprises neoplastic cells. The neoplastic cells comprising the neoplasm may be any cell type, derived from any tissue, such as an epithelial or non-epithelial cell. Examples of neoplasms and neoplastic cells encompassed by the present invention include, but are not limited to central nervous system tumours, retinoblastoma, neuroblastoma, paediatric tumours, head and neck cancers (e.g. squamous cell cancers), breast and prostate cancers, lung cancer (both small and non-small cell lung cancer), kidney cancers (e.g. renal cell adenocarcinoma), oesophagogastric cancers, hepatocellular carcinoma, pancreaticobiliary neoplasias (e.g. adenocarcinomas and islet cell tumours), colorectal cancer, cervical and anal cancers, uterine and other reproductive tract cancers, urinary tract cancers (e.g. of ureter and bladder), germ cell tumours (e.g. testicular germ cell tumours or ovarian germ cell tumours), ovarian cancer (e.g. ovarian epithelial cancers), carcinomas of unknown primary, human immunodeficiency associated malignancies (e.g. Kaposi's sarcoma), lymphomas, malignant melanomas, sarcomas, endocrine tumours (e.g. of thyroid gland), mesothelioma and other pleural or peritoneal tumours, neuroendocrine tumours and carcinoid tumours.
Preferably, the present invention is directed to the treatment of a malignant neoplastic condition and even more preferably a metastatic neoplastic condition. It would be appreciated that although the method of the invention can be applied to the treatment of any neoplasm (whether a solid tumour or not, it is particularly useful in terms of the treatment of metastasised neoplasms. Without limiting the present invention to any one theory or mode of action, non-metastasised primary tumours are treatable either by the method of the invention or by conventional treatment regimes such as surgical excision of the tumour or radiotherapy. However, tumours which have metastasised are not curable by either of these conventional treatment regimes due to the often extensive spread and growth of metastatic nodules. Accordingly, such conditions are currently only treatable by the administration of systemic chemotherapy, this treatment regime often causing severe side effects for limited curative potential, for example due to the emergence of chemoresistant neoplastic cells. Still further, even in the context of primary tumours which appear not to have metastasised, chemotherapy is still often recommended following surgery and radiation in case metastatic spread has occurred but is not yet detectable. This is a particularly common practice in the context of cancers which are traditionally regarded as aggressive, such as breast and colon cancers. The method of the present invention now provides an alternative to the application of aggressive systemic chemotherapy treatment regimes. Since the systemic administration of the DNA damaging agent of the present invention is only required to kill a proportion of the total neoplastic cell population, so as to provide a localised target for a more aggressive second step treatment regime (preferably a radioimmunotherapy regime) the occurrence of side effects can be minimised via the administration of lower doses of the DNA damaging agent, such as a cytotoxic agent, and the existence or occurrence of chemoresistant cells becomes less relevant, or at least be susceptible to elimination by means of a second-step effector activity such as a β particle, an α particle or a cytotoxin such as calicheamicin, which may exert beneficial therapeutic effects via non-crossreactive mechanisms of action.
The present invention therefore more particularly provides a method for the treatment of a malignant neoplastic condition in a subject, said method comprising:
Preferably, said malignant condition is a metastatic malignant condition. Reference to “metastatic” should be understood as a reference to a condition with either has undergone metastatisation or may have undergone metastatisation.
As detailed hereinbefore, the method of the present invention is based on a two step procedure wherein in the first step sufficient DNA damaging agent is administered to induce some neoplastic cell damage. By “damage” is meant that the integrity of the cellular and nuclear membranes is compromised such that the molecules comprising these compartment are exposed to the extracellular environment. Without limiting the present invention to any one theory or mode of action, this type of damage is usually inextricably linked to the cell death process since the permeabilisation of the cell membrane is often regarded as defining cell death. However, to the extent that this may not be the case, it should be understood that the induction of damage to the cell membrane such that the intracellular molecules are exposed to the extracellular environment falls within the scope of the present invention. Preferably, said damage is death.
According to this preferred embodiment there is provided a method for the treatment of a metastatic neoplastic condition in a subject, said method comprising:
The cell death process, whether it is induced to occur via an apoptotic mechanism or some other mechanism such as paraptosis or autophagy, ultimately results in the breakdown of the cellular structures and the exposure of both intracytoplasmic and intra-nuclear molecules (herein collectively referred to as intra-cellular molecules). Without limiting the present invention to any one theory or mode of action, the nucleus is compartmentalized structurally and functionally although membranes do not divide these compartments. The two largest interacting parts of the nucleus are DNA-containing chromatin and ribonucleoprotein (RNP)-containing structures, which include RNA. Large morphological and molecular changes in the nucleus occur during irreversible commitment to apoptosis. The classical nuclear changes of apoptosis include condensation and margination of chromatin and nuclear fragmentation. During apoptosis, it is believed that both chromatin collapse and alterations of the nuclear envelope result from the cleavage of structural nuclear proteins such as lamins and RNPs such as La, which is mediated by caspases and other proteases. Other nuclear components such as the nucleolus undergo profound structural rearrangements during apoptosis. However, during apoptosis, chromatin and RNP-containing nuclear structures remain segregated.
Molecular modifications in the nucleolus, which is composed of approximately 350 proteins and in the nucleus include up- or downregulation of protein expression or even the expression of new proteins. In addition to alterations in protein expression, apoptosis-related modifications include degradation, post-translational modification and translocation. More than 120 proteins have been reported to undergo modification during apoptosis. Approximately 20 to 40% of these proteins contain the RNA-binding domain found in RNPs which constitute only 1.8% of the human proteome.
In eukaryotic cells, the perichromatin compartment contains the machinery for transcription, splicing and gene silencing. RNPs comprise integral components of the transcriptional and splicing machinery, which are identifiable ultrastructurally as perichromatin granules (PG), perichromatin fibrils (PF) and interchromatin granules (IG). These structures may be characterized by immuno-electron microscopy using antibodies directed against the component proteins. PF contain newly synthesized RNA and PG are involved in the storage and nucleo-cytoplasmic transport of mRNA. During apoptosis, ultrastructural rearrangement of PG, PF and IG is observed and results in the creation of new fibro-granular structures called Heterogenous Ectopic RNP-Derived Structures (HERDS). These aggregates are extruded into the cytoplasm and move toward the cell surface as part of apoptotic blebs, which are eventually released as apoptotic bodies. During even the latter stages of apoptosis, RNPs in the HERDS can be labelled by specific antibodies.
The nucleolus is the dominant nuclear substructure and among other functions, it acts as a ribosome factory. During apoptosis, the nucleolus is disassembled and eventually disappears and its components may aggregate with nucleoplasmic RNPs in the nucleus, cytoplasm and apoptotic blebs. RNA molecules are also extruded from the nucleus and are readily detectable in the cytoplasm of apoptotic cells including in HERDS. However, the identification of nucleolar proteins in HERDS marks irreversible progression of HERDS formation and commitment to apoptosis.
Preferably, said intracellular molecules are nuclear molecules.
Examples of intra-cellular molecules suitable for targetting in accordance with the method of the present invention include, but are not limited to:
Preferably, said intra-cellular molecule is a nuclear molecule. Reference to “nuclear molecule” should be understood as a reference to any proteinaceous or non-proteinaceous molecule which is permanently or transiently present in the nucleus. The molecule may be one which is transiently expressed, for example in response to a specific signal, or it may be one which is constitutively expressed.
More preferably, said nuclear molecule is RNP-1, hnRNP or La. Most preferably, said nuclear molecule is La.
Accordingly, there is preferably provided a method for the treatment of a malignant neoplastic condition in a subject, said method comprising:
Preferably said nuclear molecule is La.
Reference herein to “La” includes reference to all forms of La or their homologues, or orthologs or derivatives. Reference to “La” should be understood to include reference to any isoforms which arise from alternative splicing of La mRNA or mutants or polymorphic variants of La. It should also be understood that “La” is a molecule which is alternatively termed SS-B.
Reference to the “exposure” of a nuclear molecule should be understood as a reference to rendering the subject molecule accessible to the extracellular environment such that a ligand present in the extracellular environment can interact with said molecule. To this end, it should be understood that the exposure of these molecules may occur in the context of a dead cell or a dying cell.
The selectivity of the method of the present invention is enabled by virtue of the fact that normal cells die and are cleared more quickly than neoplastic cells. Accordingly, the targeted second step treatment, if timed appropriately, can be designed to predominantly target the nuclear molecules of dead neoplastic cells by virtue of the fact that normal cells which may have been killed in the first step treatment have been, or are in the process of, clearance. However, in a related aspect it has also been determined that not only are the levels of a range of intra-cellular molecules, in particular nuclear molecules, increased upon transformation of a cell, they are still further increased upon the induction of cell death by a DNA damaging agent. This provides an additional and highly valuable mechanism by which differentiation between normal cells and neoplastic cells can occur, thereby minimising the incidence of bystander killing which targets non-malignant tissue. Without limiting the present invention to any one theory or mode of action, by minimising the availability of intra-cellular molecules, such as nuclear molecules, derived from normal cells, there occurs a reduced incidence of binding of the ligand of the second step treatment to regions of normal cellular tissue. Still further, to the extent that the targeted intra-cellular molecule is one in respect of which the levels are increased upon cellular transformation and/or cytotoxic cell death, the overall effect of the second step ligand binding is reduced in the context of normal cells due to the fact that the concentration of ligand binding to any given normal intracellular molecules is reduced due to the lower concentration of available molecule. This therefore correlates to a lower concentration of the cell death inducing effector mechanism to which the normal tissue proximally located to the normal intracellular target molecule is exposed and in fact enable the design of ligands which, per unit, exhibit a lower dose of the effector mechanism than would previously have been envisioned since increased concentration of these ligands are now enabled to be bound at any neoplastic growth of interest.
Accordingly, there is still more particularly provided a method for the treatment of a metastatic neoplastic condition in a subject, said method comprising:
As detailed hereinbefore, the DNA damaging agent which is administered in the first treatment round is one which preferably induces cell death, thereby leading to membrane permeability and exposure of the nuclear molecules of the targeted cell. Due to the fact that the objective of this treatment step is only to induce the death of a subpopulation of the subject neoplastic cells, the DNA damaging agent which is selected for use may be administered at lower doses or in some other manner which achieves this objective but which is at a lower dose than if the treatment was required to be administered in the context of being the sole systemic treatment regime. Accordingly, this minimises unwanted side effects.
Reference to a “DNA damaging agent” should be understood as a reference to any proteinaceous or non-proteinaceous agent which acts to damage cellular DNA. the agent may be a cytotoxic agent or a non-cytotoxic agent. Without limiting the present invention to any one theory or mode of action, many such agents function via the induction of apoptotic processes. However, this is not the only mechanism by which such agents function and it is conceivable that the subject DNA damage may be induced by some other mechanism. Examples of DNA damaging agents include, but are not limited to, the traditionally understood chemotherapy agents such as Actinomycin D, Arsenic Trioxide, Asparaginase, Bleomycin, Busulfan, Carboplatin, Carmustine, Chlorambucil, Cisplatin, Corticosteroids, Cyclophosphamide, Daunorubicin, Docetaxel, Doxorubicin, Epirubicin, Etoposide, Fludarabine, Fluorouracil, Gemcitabine, Hydroxyurea, Idarubicin, Ifosfamide, Irinotecan, Lomustine, Melphalan, Mercaptopurine, Methotrexate, Mitomycin, Mitoxantrone, Oxaliplatin, Paclitaxel, Procarbizine, Raltitrexed, Streptozocin, Thioguanine, Thiotepa, Topotecan, Treosulfan, Vinblastine, Vincristine, Vindesine, Vinorelbine. Other means of inducing DNA damage include ionising radiation as well as the use of molecules such as inhibitors of poly-(ADP ribosyl) transferase (PARP) or agents which induce DNA damage as part of a synergistic process with another agent, for example e.g. Gemcitabine or Irinotecan and CHK1/2 inhibitors such as CBP-501 or AZD7762. In addition, new classes of antineoplastic agents such as histone deacetylase inhibitors (HDACi) e.g. vorinostat, BH3 mimetics e.g. ABT737, and Tumor Necrosis Factor-Related Apoptotis-Inducing Ligand (TRAIL), are pro-apoptotic particularly when administered in conjunction with conventional cytotoxic agents. Hence, singly or in combination, these pro-apoptotic compounds will likely increase the amount of La-specific signal detectable in the malignant neoplasm.
Preferably, the subject agent is a radiosensitising agent. Reference to “radiosensitising agent” should be understood as a reference to an agent which potentiates the effectiveness of radiation therapy in destroying unwanted cells. For example, and without limiting the present invention to any one theory or mode of action, some radiosensitising agents function by arresting cell cycling at a stage which renders the cell particular sensitive to radiation. Examples of radiosensitising agents include, but are not limited to, platinum drugs, carmustine, topotecan, tumour necrosis factor, antimetabolites such as gemcitabine, 5-fluorouracil, capectibine, fludarabine, taxanes such as paclitaxel and docetaxel, Epidermal Growth Factor Receptor (EGFR) inhibitors such as cetuximab, erlotinib and gefitinib, histone deacetylase inhibitors such as vorinostat, DNA-dependent protein kinase inhibitors, CHK1/2 inhibitors, and hypoxic radiosensitizers such as nitroimidazole compounds.
According to this preferred embodiment there is provided a method for the treatment of a metastatic neoplastic condition in a subject, said method comprising:
Preferably, said radiosensitising agent is gemcitabine and/or cisplatin and said nuclear molecule is La.
It should be understood that the method of the present invention is not limited to the use of only one DNA damaging agent but may extend to the sequential or simultaneous use of two or more agents. It would also be appreciated that the body of knowledge in relation to the characteristics and use of DNA damaging agents is extensive and the person of skill in the art could design an administration protocol to meet the parameters of the present invention as a matter of routine procedure.
According to this preferred embodiment there is provided a method for the treatment of a metastatic neoplastic condition in a subject, said method comprising:
As detailed hereinbefore, the exposure of the nuclear molecules of a subpopulation of the neoplastic cells of interest provides a more selective target to which an effector mechanism can be targeted in order to achieve the bystander killing of proximally located viable neoplastic cells. In addition to providing a means of reducing the side effects associated with non-specific systemic treatments such as chemotherapy, this method also provides a means of reducing some of the problems associated with neoplastic cell non-responsiveness to conventional treatment regimes. Without limiting the present invention to any one theory or mode of action, systemic anti-cancer treatments usually kill by chemotherapy induced apoptosis. In many cases of advanced cancer, however, some cancer cells are resistant to the selected chemotherapy agent and conventional external beam radiotherapy may not be an available option due to the perceived or actual likelihood of the existence of metastases or micro-metastases. These resistant tumour cells are the source of clinical relapse of disease that ultimately kills most patients with advanced cancers and a significant proportion of patients with earlier stage cancers. In those patients with advanced cancers who could be shown to be responding to the initial modality of treatment because tumour cell kill could be documented in vivo, additional gains in survival and quality of life may be made if another non-cross resistant treatment modality were also to be employed either further to or, preferably, alternatively to the conventional treatment regime. Accordingly, the method of the present invention provides a means of either avoiding or else overcoming this problem by targetting a suitable therapy, such as a radiation based therapy regimen or immunotoxin, to a neoplastic condition in a manner which can target both the primary tumour and metastases. Although the general notion of targeted therapy is not new, to date the success of targeted therapy has been limited by virtue of meeting the criteria which have been required of a potential target antigen, these being:
Significant limitations exist in terms of the identification of such antigens, in particular antigens which are also ideally tumour-specific. The determination that nuclear molecules can be usefully revealed and targeted not only to provide target specificity, thereby minimising unwanted side effects, but to enable the direct in vivo delivery of radiotherapy, the external beam-based delivery of which is not suitable for the treatment of metastases or micrometastases, is therefore particularly valuable. Still further, directed delivery of radiotherapy provides a means of potentially more effectively treating metastases which are, often, chemoresistant and therefore effectively impervious to further chemotherapy.
To this end, reference to a “ligand” should be understood as a reference to any molecule having specificity (not necessarily exclusive specificity, although this is preferable) and binding affinity for a nuclear molecule. Examples of ligands include immunointeractive molecules, affibodies, phylomers, aptamers, peptidomimetic agents, lanthamide metals (which interact with RNA species), enzymatic substrates (which interact with cell death-related enzymes) and putrescine (which interacts with tissue transglutaminase). To the extent that a preferred embodiment of the present invention is directed to targetting La, said ligand is preferably an immunointeractive molecule. Although a preferred immunointeractive molecule is an immunoglobulin molecule, the present invention extends to other immunointeractive molecules such as antibody fragments, single chain antibodies, deimmunized antibodies including humanized antibodies and T-cell associated antigen-binding molecules (TABMs). Most preferably, the immunointeractive molecule is an antibody such as a polyclonal or monoclonal antibody. It should be understood that the subject ligand may be linked, bound or otherwise associated to any other proteinaceous or non-proteinaceous molecule or cell.
The ligand is “directed to” the nuclear molecule, for example La, or, to the extent that the ligand is an immunointeractive molecule, to an antigenic determinant or epitope. It should be understood that the molecule may not necessarily exhibit complete exclusivity, although this is preferable. For example, antibodies are known to sometimes crossreact with other antigens. An antigenic determinant or epitope includes that part of the molecule to which an immune response can be directed. The antigenic determinant or epitope may be a B-cell epitope or where appropriate a T-cell receptor binding molecule.
The second step of the present invention may also be designed such that a ligand is directed to one or more nuclear molecules. Accordingly, the present invention may be designed to administer two or more ligands directed to different targets, for example as a means of increasing the dose of effector mechanism which is delivered to a population of neoplastic cells. It also provides a convenient means of simultaneously delivering two different effector mechanisms.
Preferably, the subject nuclear molecule is La and the subject ligand is an antibody.
According to this preferred embodiment there is provided a method for the treatment of a neoplastic condition in a subject, said method comprising:
Preferably, said DNA damaging agent is a radiosensitising agent or a cytotoxic agent such as calicheamicin or a maytansinoid.
25
The use of antibodies, in particular monoclonal antibodies, to detect nuclear molecules such a La is a preferred method of the present invention. Discussion hereinafter in relation to La should be understood as non-limiting and is intended to be exemplary of any cellular antigen. Antibodies may be prepared by any of a number of means. For the detection of human La, for example, human-human monoclonal antibody hybridomas may be derived from B cells, which have been obtained from patients who make anti-La autoantibodies because they have systemic autoimmune diseases such as systemic lupus erythematosis (SLE) or Sjorgren's syndrome (Ravirajan et al. Lupus 1(3):157-165, 1992). Antibodies are generally but not necessarily derived from non-human animals such as primates, livestock animals (e.g. sheep, cows, pigs, goats, horses), laboratory test animals (e.g. mice, rats, guinea pigs, rabbits) and companion animals (e.g. dogs, cats). Generally, antibody based assays are conducted in vitro on cell or tissue biopsies. However, if an antibody is suitably deimmunized or, in the case of human use, humanized, then the antibody can be labelled with, for example, a nuclear tag, administered to a patient and the site of nuclear label accumulation determined by radiological techniques. The La antibody is regarded, therefore, as a cellular apoptosis targeting agent. Accordingly, the present invention extends to deimmunized forms of the antibodies for use in cellular apoptosis imaging in human and non-human patients. This is described further below.
Currently available antibodies include SW3 and 3B9.
For the generation of antibodies to La, this molecule is required to be extracted from a biological sample whether this be from animal including human tissue or from cell culture if produced by recombinant means. The La can be separated from the biological sample by any suitable means. For example, the separation may take advantage of any one or more of La's surface charge properties, size, density, biological activity and its affinity for another entity (e.g. another protein or chemical compound to which it binds or otherwise associates). Thus, for example, separation of La from the biological fluid may be achieved by any one or more of ultra-centrifugation, ion-exchange chromatography (e.g. anion exchange chromatography, cation exchange chromatography), electrophoresis (e.g. polyacrylamide gel electrophoresis, isoelectric focussing), size separation (e.g., gel filtration, ultra-filtration) and affinity-mediated separation (e.g. immunoaffinity separation including, but not limited to, magnetic bead separation such as Dynabead™ separation, immunochromatography, immuno-precipitation). Choice of the separation technique(s) employed may depend on the biological activity or physical properties of the La sought or from which tissues it is obtained.
Preferably, the separation of La from the biological fluid preserves conformational epitopes present on the protein and, thus, suitably avoids techniques that cause denaturation of the enzyme. Persons of skill in the art will recognize the importance of maintaining or mimicking as close as possible physiological conditions peculiar to La (e.g. the biological fluid from which it is obtained) to ensure that the antigenic determinants or active sites on La, which are exposed to the animal, are structurally identical to that of the native protein. This ensures the raising of appropriate antibodies in the immunised animal that would recognize the native protein. In a preferred embodiment, La is separated from the biological fluid using any one or more of affinity separation, gel filtration and ultra-filtration.
Immunization and subsequent production of monoclonal antibodies can be carried out using standard protocols as for example described by Kohler and Milstein, Nature 256. 495-499, 1975; Kohler and Milstein, Eur. J. Immunol. 6(7): 511-519, 1976; Coligan et al., Current Protocols in Immunology, John Wiley & Sons, Inc., 1991-1997, or Toyama et al., “Monoclonal Antibody, Experiment Manual”, published by Kodansha Scientific, 1987. Essentially, an animal is immunized with a La-containing biological fluid or fraction thereof by standard methods to produce antibody-producing cells, particularly antibody-producing somatic cells (e.g. B lymphocytes). These cells can then be removed from the immunized animal for immortalization. Where a fragment of La is used to generate antibodies, it may need to first be associated with a carrier. By “carrier” is meant any substance of typically high molecular weight to which a non- or poorly immunogenic substance (e.g. a hapten) is naturally or artificially linked to enhance its immunogenicity.
Immortalization of antibody-producing cells may be carried out using methods which are well-known in the art. For example, the immortalization may be achieved by the transformation method using Epstein-Barr virus (EBV) (Kozbor et al., Methods in Enzymology 121: 140, 1986). In a preferred embodiment, antibody-producing cells are immortalized using the cell fusion method (described in Coligan et al., 1991-1997, supra), which is widely employed for the production of monoclonal antibodies. In this method, somatic antibody-producing cells with the potential to produce antibodies, particularly B cells, are fused with a myeloma cell line. These somatic cells may be derived from the lymph nodes, spleens and peripheral blood of humans with circulating La-reactive antibodies, and primed animals, preferably rodent animals such as mice and rats. Mice spleen cells are particularly useful. It would be possible, however, to use rat, rabbit, sheep or goat cells, or cells from other animal species instead.
Specialized myeloma cell lines have been developed from lymphocytic tumours for use in hybridoma-producing fusion procedures (Kohler and Milstein, 1976, supra; Shulman et al., Nature 276: 269-270, 1978; Volk et al., J. Virol. 42(1): 220-227, 1982). These cell lines have been developed for at least three reasons. The first is to facilitate the selection of fused hybridomas from unfused and similarly indefinitely self-propagating myeloma cells. Usually, this is accomplished by using myelomas with enzyme deficiencies that render them incapable of growing in certain selective media that support the growth of hybridomas. The second reason arises from the inherent ability of lymphocytic tumour cells to produce their own antibodies. To eliminate the production of tumour cell antibodies by the hybridomas, myeloma cell lines incapable of producing endogenous light or heavy immunoglobulin chains are used. A third reason for selection of these cell lines is for their suitability and efficiency for fusion.
Many myeloma cell lines may be used for the production of fused cell hybrids, including, e.g. P3X63-Ag8, P3X63-AG8.653, P3/NS1-Ag4-1 (NS-1), Sp2/0-Ag14 and S194/5.XXO.Bu.1. The P3X63-Ag8 and NS-1 cell lines have been described by Köler and Milstein (1976, supra). Shulman et al. (1978, supra) developed the Sp2/0-Ag14 myeloma line. The S194/5.XXO.Bu.1 line was reported by Trowbridge, J. Exp. Med. 148(1): 313-323, 1978.
Methods for generating hybrids of antibody-producing spleen or lymph node cells and myeloma cells usually involve mixing somatic cells with myeloma cells in a 10:1 proportion (although the proportion may vary from about 20:1 to about 1:1), respectively, in the presence of an agent or agents (chemical, viral or electrical) that promotes the fusion of cell membranes. Fusion methods have been described (Kohler and Milstein, 1975, supra; 1976, supra; Gefter et al., Somatic Cell Genet. 3: 231-236, 1977; Volk et al., 1982, supra). The fusion-promoting agents used by those investigators were Sendai virus and polyethylene glycol (PEG).
Because fusion procedures produce viable hybrids at very low frequency (e.g. when spleens are used as a source of somatic cells, only one hybrid is obtained for roughly every 1×105 spleen cells), it is preferable to have a means of selecting the fused cell hybrids from the remaining unfused cells, particularly the unfused myeloma cells. A means of detecting the desired antibody-producing hybridomas among other resulting fused cell hybrids is also necessary. Generally, the selection of fused cell hybrids is accomplished by culturing the cells in media that support the growth of hybridomas but prevent the growth of the unfused myeloma cells, which normally would go on dividing indefinitely. The somatic cells used in the fusion do not maintain long-term viability in in vitro culture and hence do not pose a problem. In the example of the present invention, myeloma cells lacking hypoxanthine phosphoribosyl transferase (HPRT-negative) were used. Selection against these cells is made in hypoxanthine/aminopterin/thymidine (HAT) medium, a medium in which the fused cell hybrids survive due to the HPRT-positive genotype of the spleen cells. The use of myeloma cells with different genetic deficiencies (drug sensitivities, etc.) that can be selected against in media supporting the growth of genotypically competent hybrids is also possible.
Several weeks are required to selectively culture the fused cell hybrids. Early in this time period, it is necessary to identify those hybrids which produce the desired antibody, so that they may subsequently be cloned and propagated. Generally, around 10% of the hybrids obtained produce the desired antibody, although a range of from about 1 to about 30% is not uncommon. The detection of antibody-producing hybrids can be achieved by any one of several standard assay methods, including enzyme-linked immunoassay and radioimmunoassay techniques as, for example, described in Kennet et al. (eds) Monoclonal Antibodies and Hybridomas: A New Dimension in Biological Analyses, pp. 376-384, Plenum Press, New York, 1980 and by FACS analysis.
Once the desired fused cell hybrids have been selected and cloned into individual antibody-producing cell lines, each cell line may be propagated in either of two standard ways. A suspension of the hybridoma cells can be injected into a histocompatible animal. The injected animal will then develop tumours that secrete the specific monoclonal antibody produced by the fused cell hybrid. The body fluids of the animal, such as serum or ascites fluid, can be tapped to provide monoclonal antibodies in high concentration. Alternatively, the individual cell lines may be propagated in vitro in laboratory culture vessels. The culture medium containing high concentrations of a single specific monoclonal antibody can be harvested by decantation, filtration or centrifugation, and subsequently purified.
The cell lines are tested for their specificity to detect the La by any suitable immunodetection means. For example, cell lines can be aliquoted into a number of wells and incubated and the supernatant from each well is analyzed by enzyme-linked immunosorbent assay (ELISA), indirect fluorescent antibody technique, or the like. The cell line(s) producing a monoclonal antibody capable of recognizing the target La but which does not recognize non-target epitopes are identified and then directly cultured in vitro or injected into a histocompatible animal to form tumours and to produce, collect and purify the required antibodies.
These antibodies are La specific. This means that the antibodies are capable of distinguishing La from other molecules. More broad spectrum antibodies may be used provided that they do not cross react with molecules in a normal cell.
In one embodiment, the subject antibody is anti-human La monoclonal antibodies, 8G3 and 9A5 (Bachmann et al. Proc Natl Acad Sci USA 83 (20):7770-7774, 1986), anti-human La monoclonal antibody (mAb), La1B5 (Mamula et al. J Immunol 143(9):2923-2928, 1989), anti-human La monoclonal antibodies (Carmo-Fonseca et al. ExpCell Res 185(1):73-85, 1989), anti-human and anti-bovine La monoclonal antibodies, SW1, SW3 and SW5 (Pruijn et al. Eur J Biochem 232(2):611-619, 1995), anti-human and anti-rodent La mAb, La4B6 (Troster et al. J Autoimmunity 8(6):825-842, 1995) or anti-human and anti-murine La mAb, 3B9 (Tran et al. Arthritis Rheum 46(1): 202-208, 2002) or derivative, homologue, analogue, chemical equivalent, mutant or mimetic thereof.
Since the monoclonal antibody is destined for in vivo use, it may be desirable to deimmunise the antibody. The deimmunization process may take any of a number of forms including the preparation of chimeric antibodies which have the same or similar specificity as the monoclonal antibodies prepared according to the present invention. Chimeric antibodies are antibodies whose light and heavy chain genes have been constructed, typically by genetic engineering, from immunoglobulin variable and constant region genes belonging to different species. Thus, in accordance with the present invention, once a hybridoma producing the desired monoclonal antibody is obtained, techniques are used to produce interspecific monoclonal antibodies wherein the binding region of one species is combined with a non-binding region of the antibody of another species (Liu et al., Proc. Natl. Acad. Sci. USA 84: 3439-3443, 1987). For example, complementary determining regions (CDRs) from a non-human (e.g. murine) monoclonal antibody can be grafted onto a human antibody, thereby “humanizing” the murine antibody (European Patent Publication No. 0 239 400; Jones et al., Nature 321: 522-525, 1986; Verhoeyen et at, Science 239: 1534-1536, 1988; Richmann et al., Nature 332: 323-327, 1988). In this case, the deimmunizing process is specific for humans. More particularly, the CDRs can be grafted onto a human antibody variable region with or without human constant regions. The non-human antibody providing the CDRs is typically referred to as the “donor” and the human antibody providing the framework is typically referred to as the “acceptor”. Constant regions need not be present, but if they are, they must be substantially identical to human immunoglobulin constant regions, i.e. at least about 85-90%, preferably about 95% or more identical. Hence, all parts of a humanized antibody, except possibly the CDRs, are substantially identical to corresponding parts of natural human immunoglobulin sequences. Thus, a “humanized antibody” is an antibody comprising a humanized light chain and a humanized heavy chain immunoglobulin. A donor antibody is said to be “humanized”, by the process of “humanization”, because the resultant humanized antibody is expected to bind to the same antigen as the donor antibody that provides the CDRs. Reference herein to “humanized” includes reference to an antibody deimmunized to a particular host, in this case, a human host.
It will be understood that the deimmunized antibodies may have additional conservative amino acid substitutions which have substantially no effect on antigen binding or other immunoglobulin functions. Exemplary conservative substitutions may be made according to Table 1.
Exemplary methods which may be employed to produce deimmunized antibodies according to the present invention are described, for example, in references Richmann et al., 1988, supra; European Patent Publication No. 0 239 400; Chou et al. (U.S. Pat. No. 6,056,957); Queen et al. (U.S. Pat. No. 6,180,370); Morgan et al. (U.S. Pat. No. 6,180,377).
Thus, in one embodiment, the present invention contemplates the use of a deimmunized antibody molecule having specificity for an epitope recognized by a monoclonal antibody to La wherein at least one of the CDRs of the variable domain of said deimmunized antibody is derived from the said monoclonal antibody to La and the remaining immunoglobulin-derived parts of the deimmunized antibody molecule are derived from an immunoglobulin or an analogue thereof from the host for which the antibody is to be deimmunized.
This aspect of the present invention involves manipulation of the framework region of a non-human antibody.
The present invention extends to the use of mutants, analogues and derivatives of the subject antibodies but which still retain specificity for La.
The terms “mutant” or “derivatives” includes one or more amino acid substitutions, additions and/or deletions.
As used herein, the term “CDR” includes CDR structural loops which covers the three light chain and the three heavy chain regions in the variable portion of an antibody framework region which bridge β strands on the binding portion of the molecule. These loops have characteristic canonical structures (Chothia et al., J. Mol. Biol. 196: 901, 1987; Chothia et al., J. Mol. Biol. 227: 799, 1992).
By “framework region” is meant region of an immunoglobulin light or heavy chain variable region, which is interrupted by three hypervariable regions, also called CDRs. The extent of the framework region and CDRs have been precisely defined (see, for example, Kabat et al., “Sequences of Proteins of Immunological Interest”, U.S. Department of Health and Human Services, 1983). The sequences of the framework regions of different light or heavy chains are relatively conserved within a species. As used herein, a “human framework region” is a framework region that is substantially identical (about 85% or more, usually 90-95% or more) to the framework region of a naturally occurring human immunoglobulin. The framework region of an antibody, that is the combined framework regions of the constituent light and heavy chains, serves to position and align the CDRs. The CDRs are primarily responsible for binding to an epitope of La.
As used herein, the term “heavy chain variable region” means a polypeptide which is from about 110 to 125 amino acid residues in length, the amino acid sequence of which corresponds to that of a heavy chain of a monoclonal antibody of the invention, starting from the amino-terminal (N-terminal) amino acid residue of the heavy chain. Likewise, the term “light chain variable region” means a polypeptide which is from about 95 to 130 amino acid residues in length, the amino acid sequence of which corresponds to that of a light chain of a monoclonal antibody of the invention, starting from the N-terminal amino acid residue of the light chain. Full-length immunoglobulin “light chains” (about 25 Kd or 214 amino acids) are encoded by a variable region gene at the NH2-terminus (about 110 amino acids) and a κ or λ constant region gene at the COOH-terminus. Full-length immunoglobulin “heavy chains” (about 50 Kd or 446 amino acids), are similarly encoded by a variable region gene (about 116 amino acids) and one of the other aforementioned constant region genes, e.g. γ (encoding about 330 amino acids).
The term “immunoglobulin” or “antibody” is used herein to refer to a protein consisting of one or more polypeptides substantially encoded by immunoglobulin genes. The recognized immunoglobulin genes include the κ, λ, α, γ (IgG1, IgG2, IgG3, IgG4), δ, ε and μ constant region genes, as well as the myriad immunoglobulin variable region genes. One form of immunoglobulin constitutes the basic structural unit of an antibody. This form is a tetramer and consists of two identical pairs of immunoglobulin chains, each pair having one light and one heavy chain. In each pair, the light and heavy chain variable regions are together responsible for binding to an antigen, and the constant regions are responsible for the antibody effector functions. In addition to antibodies, immunoglobulins may exist in a variety of other forms including, for example, Fv, Fab, Fab′ and (Fab′)2.
The invention also contemplates the use and generation of fragments of monoclonal antibodies produced by the method of the present invention including, for example, Fv, Fab, Fab′ and F(ab′)2 fragments. Such fragments may be prepared by standard methods as for example described by Coligan et al. (1991-1997, supra).
The present invention also contemplates synthetic or recombinant antigen-binding molecules with the same or similar specificity as the monoclonal antibodies of the invention. Antigen-binding molecules of this type may comprise a synthetic stabilised Fv fragment. Exemplary fragments of this type include single chain Fv fragments (sFv, frequently termed scFv) in which a peptide linker is used to bridge the N terminus or C terminus of a VH domain with the C terminus or N-terminus, respectively, of a VL domain. ScFv lack all constant parts of whole antibodies and are not able to activate complement. Suitable peptide linkers for joining the VH and VL domains are those which allow the VH and VL domains to fold into a single polypeptide chain having an antigen binding site with a three dimensional structure similar to that of the antigen binding site of a whole antibody from which the Fv fragment is derived. Linkers having the desired properties may be obtained by the method disclosed in U.S. Pat. No. 4,946,778. However, in some cases a linker is absent. ScFvs may be prepared, for example, in accordance with methods outlined in Krebber et al. (Krebber et al., J. Immunol. Methods 201(1): 35-55, 1997). Alternatively, they may be prepared by methods described in U.S. Pat. No. 5,091,513, European Patent No 239,400 or the articles by Winter and Milstein (Winter and Milstein, Nature 349: 293, 1991) and Plückthun et al. (Plückthun et al., In Antibody engineering: A practical approach 203-252, 1996).
Alternatively, the synthetic stabilized Fv fragment comprises a disulphide stabilized Fv (dsFv) in which cysteine residues are introduced into the VH and VL domains such that in the fully folded Fv molecule the two residues will form a disulphide bond therebetween. Suitable methods of producing dsFv are described, for example, in (Glockshuber et al., Biochem. 29: 1363-1367, 1990; Reiter et al., Biochem. 33: 5451-5459, 1994; Reiter et al., Cancer Res. 54: 2714-2718, 1994; Reiter et al., J. Biol. Chem. 269: 18327-18331, 1994; Webber et al., Mol. Immunol. 32: 249-258, 1995).
Also contemplated as synthetic or recombinant antigen-binding molecules are single variable region domains (termed dAbs) as, for example, disclosed in (Ward et al., Nature 341: 544-546, 1989; Hamers-Casterman et al., Nature 363: 446-448, 1993; Davies & Riechmann, FEBS Lett. 339: 285-290, 1994).
Alternatively, the synthetic or recombinant antigen-binding molecule may comprise a “minibody”.
In this regard, minibodies are small versions of whole antibodies, which encode in a single chain the essential elements of a whole antibody. Suitably, the minibody is comprised of the VH and VL domains of a native antibody fused to the hinge region and CH3 domain of the immunoglobulin molecule as, for example, disclosed in U.S. Pat. No. 5,837,821.
In an alternate embodiment, the synthetic or recombinant antigen binding molecule may comprise non-immunoglobulin derived, protein frameworks. For example, reference may be made to (Ku & Schutz, Proc. Natl. Acad. Sci. USA 92: 6552-6556, 1995) which discloses a four-helix bundle protein cytochrome b562 having two loops randomized to create CDRs, which have been selected for antigen binding.
The synthetic or recombinant antigen-binding molecule may be multivalent (i.e. having more than one antigen binding site). Such multivalent molecules may be specific for one or more antigens. Multivalent molecules of this type may be prepared by dimerization of two antibody fragments through a cysteinyl-containing peptide as, for example disclosed by (Adams et al., Cancer Res. 53: 4026-4034, 1993; Cumber et al., J. Immunol. 149: 120-126, 1992). Alternatively, dimerization may be facilitated by fusion of the antibody fragments to amphiphilic helices that naturally dimerize (Pliinckthun, Biochem. 31: 1579-1584, 1992) or by use of domains (such as leucine zippers jun and fos) that preferentially heterodimerize (Kostelnv et al., J. Immunol. 148: 1547-1553, 1992).
The present invention further encompasses chemical analogues of amino acids in the subject antibodies. The use of chemical analogues of amino acids is useful inter alia to stabilize the molecules such as if required to be administered to a subject. The analogues of the amino acids contemplated herein include, but are not limited to, modifications of side chains, incorporation of unnatural amino acids and/or their derivatives during peptide, polypeptide or protein synthesis and the use of crosslinkers and other methods which impose conformational constraints on the proteinaceous molecule or their analogues.
Examples of side chain modifications contemplated by the present invention include modifications of amino groups such as by reductive alkylation by reaction with an aldehyde followed by reduction with NaBH4; amidination with methylacetimidate; acylation with acetic anhydride; carbamoylation of amino groups with cyanate; trinitrobenzylation of amino groups with 2,4,6-trinitrobenzene sulphonic acid (TNBS); acylation of amino groups with succinic anhydride and tetrahydrophthalic anhydride; and pyridoxylation of lysine with pyridoxal-5-phosphate followed by reduction with NaBH4.
The guanidine group of arginine residues may be modified by the formation of heterocyclic condensation products with reagents such as 2,3-butanedione, phenylglyoxal and glyoxal.
The carboxyl group may be modified by carbodiimide activation via O-acylisourea formation followed by subsequent derivatisation, for example, to a corresponding amide. Sulphydryl groups may be modified by methods such as carboxymethylation with iodoacetic acid or iodoacetamide; performic acid oxidation to cysteic acid; formation of a mixed disulphides with other thiol compounds; reaction with maleimide, maleic anhydride or other substituted maleimide; formation of mercurial derivatives using 4-chloromercuribenzoate, 4-chloromercuriphenylsulphonic acid, phenylmercury chloride, 2-chloromercuri-4-nitrophenol and other mercurials; carbamoylation with cyanate at alkaline pH.
Tryptophan residues may be modified by, for example, oxidation with N-bromosuccinimide or alkylation of the indole ring with 2-hydroxy-5-nitrobenzyl bromide or sulphenyl halides. Tyrosine residues on the other hand, may be altered by nitration with tetranitromethane to form a 3-nitrotyrosine derivative.
Modification of the imidazole ring of a histidine residue may be accomplished by alkylation with iodoacetic acid derivatives or N-carbethoxylation with diethylpyrocarbonate.
Examples of incorporating unnatural amino acids and derivatives during peptide synthesis include, but are not limited to use of norleucine, 4-amino butyric acid, 4-amino-3-hydroxy-5-phenylpentanoic acid, 6-aminohexanoic acid, t-butylglycine, norvaline, phenylglycine, ornithine, sarcosine, 4-amino-3-hydroxy-6-methylheptanoic acid, 2-thienyl alanine and/or D-isomers of amino acids. A list of unnatural amino acid, contemplated herein is shown in Table 2.
Crosslinkers can be used, for example, to stabilize 3D conformations, using homo-bifunctional crosslinkers such as the bifunctional imido esters having (CH2)n spacer groups with n=1 to n=6, glutaraldehyde, N-hydroxysuccinimide esters and hetero-bifunctional reagents which usually contain an amino-reactive moiety such as N-hydroxysuccinimide and another group specific-reactive moiety such as maleimido or dithio moiety (SH) or carbodiimide (COOH).
Without limiting the present invention to any one theory or mode of action, it has been observed that immunointractive molecules directed to La may become fixed, thereby providing a robust bystander effector mechanism. Still further, La has also been observed to become localised to the cellular cytoplasm, subsequently to the induction of cell damage, or may become associated with apoptotic bodies.
The ligand hereinbefore described is designed to deliver to the tumour site an anti-neoplastic treatment regime designed to downregulate the growth of the tumour cells or, most preferably, induce the death of these cells. To this end, reference to an “effector mechanism” should be understood as a reference to any suitable mechanism which, when localised to the site of neoplastic cells (by virtue of the ligand based targetting), either directly or indirectly downregulates the growth of, and preferably kills, proximally located viable neoplastic cells. The effector mechanism may be any proteinaceous or non-proteinaceous molecule or group of molecules which achieve this outcome. Examples of effector mechanisms suitable for use in the method of the present invention include, but are not limited to:
Reference to an effector mechanism being “associated” with a ligand, for example, an antibody or other immunointeractive molecule should be understood as a reference to any covalent or non-covalent interactive mechanism which achieves linking of the two molecules. This includes, but is not limited to the use of peptide bonds, ionic bonds, hydrogen bonds, van Der Waals forces or any other interactive bonding mechanism.
It would be appreciated that the two steps of the present invention are preferably performed sequentially. However, it should also be understood that this method may be modified to incorporate other steps. For example, one may seek to perform a diagnostic/screening step after administration of the DNA damaging agent in order to assess the effectiveness of the first step. Such screening step may also be applied later in the treatment regime to monitor the effectiveness of the treatment. It would also be appreciated that it is well within the skill of the person in the art, and in light of the teaching provided herein, to select and design an administration protocol for the elements herein described including, for example, the DNA damaging agent, target nuclear molecule, ligand and the effector mechanism.
Reference to “growth” of a cell or neoplasm should be understood as a reference to the proliferation, differentiation and/or maintenance of viability of the subject cell, while “down-regulating the growth” of a cell or neoplasm is a reference to the process of cellular senescence or to reducing, preventing or inhibiting the proliferation, differentiation and/or maintenance of viability of the subject cell. In a preferred embodiment the subject growth is proliferation and the subject down-regulation is killing. In this regard, killing may be achieved either by delivering a fatal hit to the cell or by delivering to the cell a signal which induces the cell to apoptose.
In a particularly preferred embodiment there is provided a method for the treatment of a neoplastic tumour in a subject, said method comprising:
Preferably, said radiosensitising agent is one or more of Camptosar, Cisplatin, Docetaxel,
Gemcitabina, Gemcitabine, Gemzar, Irinotecan, Platinex, Platinol, Trihydrate, Vinorelbina, Vinorelbine and said radioisotope is 90Y or 213Bi.
More preferably, said immunointeractive molecule is a monoclonal antibody.
Still more preferably, said neoplastic tumour is metastatic.
Reference herein to a “subject” should be understood to encompass humans, primates, livestock animals (eg. sheep, pigs, cattle, horses, donkeys), laboratory test animals (eg. mice, rabbits, rats, guinea pigs), companion animals (eg. dogs, cats) and captive wild animals (eg. foxes, kangaroos, deer). Preferably, the mammal is a human.
It should be understood that the term “treatment” does not necessarily imply that a subject is treated until total recovery. Accordingly, treatment includes reducing the severity of an existing condition, amelioration of the symptoms of a particular condition or preventing or otherwise reducing the risk of developing a particular condition.
Administration of the DNA damaging agent and the ligand, in the form of pharmaceutical compositions, may be performed by any convenient means. The pharmaceutical composition is contemplated to exhibit therapeutic activity when administered in an amount which depends on the particular case. The variation depends, for example, on the human or animal and the particular agent, ligand and effector mechanism selected for use. A broad range of doses may be applicable. Dosage regimes may be adjusted to provide the optimum therapeutic response.
Routes of administration include, but are not limited to, respiratorally, intratracheally, nasopharyngeally, intravenously, intraperitoneally, subcutaneously, intracranially, intradermally, intramuscularly, intraoccularly, intrathecally, intracereberally, intranasally, infusion, orally, rectally, via IV drip patch and implant.
In accordance with these methods, the agent defined in accordance with the present invention may be coadministered with one or more other compounds or molecules. By “coadministered” is meant simultaneous administration in the same formulation or in two different formulations via the same or different routes or sequential administration by the same or different routes. For example, the subject agent may be administered together with an agonistic agent in order to enhance its effects. By “sequential” administration is meant a time difference of from seconds, minutes, hours or days between the administration of the two types of molecules. These molecules may be administered in any order.
Another aspect of the present invention is directed to the use of:
Examples of neoplasms and neoplastic cells encompassed by the present invention include, but are not limited central nervous system tumours, retinoblastoma, neuroblastoma, paediatric tumours, head and neck cancers (eg. squamous cell cancers), breast and prostate cancers, lung cancer (both small and non-small cell lung cancer), kidney cancers (eg. renal cell adenocarcinoma), oesophagogastric cancers, hepatocellular carcinoma, pancreaticobiliary neoplasias (eg. adenocarcinomas and islet cell tumours), colorectal cancer, cervical and anal cancers, uterine and other reproductive tract cancers, urinary tract cancers (eg. of ureter and bladder), germ cell tumours (eg. testicular germ cell tumours or ovarian germ cell tumours), ovarian cancer (eg. ovarian epithelial cancers), carcinomas of unknown primary, human immunodeficiency associated malignancies (eg. Kaposi's sarcoma), lymphomas, malignant melanomas, sarcomas, endocrine tumours (eg. of thyroid gland), mesothelioma and other pleural tumours, neuroendocrine tumours and carcinoid tumours.
More particular aspects in relation to the DNA damaging agent, intracellular molecule, ligand, effector mechanism and cell damage are hereinbefore described in detail.
In yet another further aspect, the present invention contemplates a pharmaceutical composition comprising the agents as hereinbefore defined together with one or more pharmaceutically acceptable carriers and/or diluents. Said agents are referred to as the active ingredients.
The pharmaceutical forms are preferably suitable for injectable use and include sterile aqueous solutions (where water soluble) or dispersions and sterile powders for the extemporaneous preparation of sterile injectable solutions or dispersion. It must be stable under the conditions of manufacture and storage and must be preserved against the contaminating action of microorganisms such as bacteria and fungi. The carrier can be a solvent or dispersion medium containing, for example, water, ethanol, polyol (for example, glycerol, propylene glycol and liquid polyethylene glycol, and the like), suitable mixtures thereof, and vegetable oils. The proper fluidity can be maintained, for example, by the use of a coating such as lecithin, by the maintenance of the required particle size in the case of dispersion and by the use of superfactants. The preventions of the action of microorganisms can be brought about by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, sorbic acid, thimerosal and the like. In many cases, it will be preferable to include isotonic agents, for example, sugars or sodium chloride. Prolonged absorption of the injectable compositions can be brought about by the use in the compositions of agents delaying absorption, for example, aluminum monostearate and gelatin.
Sterile injectable solutions are prepared by incorporating the active compounds in the required amount in the appropriate solvent with various of the other ingredients enumerated above, as required, followed by filtered sterilisation. Generally, dispersions are prepared by incorporating the various sterilised active ingredient into a sterile vehicle which contains the basic dispersion medium and the required other ingredients from those enumerated above. In the case of sterile powders for the preparation of sterile injectable solutions, the preferred methods of preparation are vacuum drying and the freeze-drying technique which yield a powder of the active ingredient plus any additional desired ingredient from previously sterile-filtered solution thereof.
When the active ingredients are suitably protected they may be orally administered, for example, with an inert diluent or with an assimilable edible carrier, or it may be enclosed in hard or soft shell gelatin capsule, or it may be compressed into tablets, or it may be incorporated directly with the food of the diet. It would be appreciated, for example, that some chemotherapy agents can be delivered orally. For oral therapeutic administration, the active compound may be incorporated with excipients and used in the form of ingestible tablets, buccal tablets, troches, capsules, elixirs, suspensions, syrups, wafers, and the like. Such compositions and preparations should contain at least 1% by weight of active compound. The percentage of the compositions and preparations may, of course, be varied and may conveniently be between about 5 to about 80% of the weight of the unit. The amount of active compound in such therapeutically useful compositions in such that a suitable dosage will be obtained. Preferred compositions or preparations according to the present invention are prepared so that an oral dosage unit form contains between about 0.1 μg and 2000 mg of active compound.
The tablets, troches, pills, capsules and the like may also contain the components as listed hereafter: a binder such as gum, acacia, corn starch or gelatin; excipients such as dicalcium phosphate; a disintegrating agent such as corn starch, potato starch, alginic acid and the like; a lubricant such as magnesium stearate; and a sweetening agent such as sucrose, lactose or saccharin may be added or a flavouring agent such as peppermint, oil of wintergreen, or cherry flavouring. When the dosage unit form is a capsule, it may contain, in addition to materials of the above type, a liquid carrier. Various other materials may be present as coatings or to otherwise modify the physical form of the dosage unit. For instance, tablets, pills, or capsules may be coated with shellac, sugar or both. A syrup or elixir may contain the active compound, sucrose as a sweetening agent, methyl and propylparabens as preservatives, a dye and flavouring such as cherry or orange flavour. Of course, any material used in preparing any dosage unit form should be pharmaceutically pure and substantially non-toxic in the amounts employed. In addition, the active compound(s) may be incorporated into sustained-release preparations and formulations.
Yet another aspect of the present invention is directed to a kit comprising a DNA damaging agent and an intracellular molecule ligand associated with an effector mechanism.
More particular aspects in relation to the DNA damaging agent, the intracellular molecule, ligand and effector mechanism are hereinbefore defined in detail.
The present invention is further described by reference to the following non-limiting examples.
Cell culture media, RPMI-1640, DMEM and Ham's F12, and fetal calf serum (FCS) were all purchased from JRH Biosciences Inc. (KS, USA). Trypsin-EDTA solution, trypan blue, propidium iodide (PI), bovine serum albumin (BSA), hydrocortisone and staurosporine (STS) were obtained from Sigma-Aldrich Co. (MO, USA). Hybond-P membrane (PVDF), ECF™ substrate, L-[U-14C]Leucine, D-[U-14C]Glucose and Protein G purification columns were purchased from Amersham Biosciences, (NJ, USA). The miniPERM bioreactor was obtained from Vivascience (Hannover, Germany) and the BCA Protein Reagent Assay from Pierce Biotechnology Inc. (IL, USA). Solvable™ and UltimaGold™ were purchased from PerkinElmer Inc. (MA, USA). H2O2. The anti-poly(ADP-ribose) polymerase (PARP) monoclonal antibody (IgG1 mAb) clone C-2-10 was obtained from Oncogene™ Research Products (EMD Biosciences Inc., CA, USA). The anti-actin (N-20) affinity purified goat polyclonal antibody was purchased from Santa Cruz Biotechnology Inc. (CA, USA). Goat anti-mouse IgG alkaline phosphatase (AP)-conjugated antibody and rabbit anti-goat IgG AP-conjugated antibody were purchased from Johnson Laboratories (USA). The anti-La/SS-B IgG mAb 3B9 cell line (Tran et al., 2002), prepared by Dr M. Bachmann (Oklahoma Medical Research Foundation, Okla., USA), was a generous gift from Dr T.P. Gordon (Department of Immunology, Allergy, and Arthritis, Flinders Medical Centre, SA, Australia). The irrelevant 1D4.5 mAb Sal5 cell line, prepared by Dr L.K. Ashman (Medical Science Building, University of Newcastle, NSW, Australia), was a kind gift from Dr S. McColl (School of Molecular Biosciences, University of Adelaide, SA, Australia). These mAbs were affinity-purified on Protein G purification columns. Purified 3B9 and Sal5 mAbs were conjugated to fluorescein isothiocyanate (FITC) as described by manufacturer's instructions Sigma-Aldrich Co. (MO, USA). Anti-mouse IgG antibody conjugated to Alexa488 and 7-AAD were purchased from Molecular Probes® (Invitrogen, USA). Lymphoprep™ was purchased from Axis-Shield PoC AS (Oslo, Norway). Etoposide and vincristine for injection (Pfizer Inc., NY, USA) and cyclophosphamide, cisplatin were purchased.
The tumour cell lines, Jurkat (ATCC# TIB-152, acute T cell leukemia), EL4 (ATCC# TIB-39, mouse T-lymphocyte lymphoma), U-937 (ATCC# CRL-1593.2, monocytic leukemia) and Raji (ATCC# CCL-86, Burkitt's lymphoma) were routinely grown as suspension cultures in RPMI-1640 containing 5 FCS and passaged every 48-72 h at 1:4 dilution. The U2OS osteosarcoma cell line (ATCC# HTB-96), SAOS-2 osteosarcoma cell line (ATCC# HTB-85) and HeLa cervical adenocarcinoma (ATCC# CCL-2) were routinely cultured in DMEM containing 5% FCS and passaged every 48-72 h after detachment using trypsin-EDTA solution. The squamous cell carcinoma cell line, SCC-25 (ATCC# CRL-1628), was cultured in a 1:1 mixture of DMEM and Ham's F12 medium containing supplemented with 400 ng/mL hydrocortisone and 10% FCS and passaged after detachment using trypsin-EDTA solution. Fresh blood from normal volunteers was subjected to Lymphoprep® separation to isolate peripheral blood monocytic cells (PBMC). PBMC were cultured overnight in RPMI-1640 and 5 FCS to separate suspension and adherent cells. The cells in suspension were defined as lymphocytes because more than 70% were CD3+ whereas the adherent cells were defined as monocytes because more than 70% were CD14+. Mouse thymocytes were obtained from mice. Finally, buccal cells were isolated from the gum lining of healthy volunteers as described.
Apoptosis in all cultures was induced by incubation of these cells in culture media described above and in the presence of specified concentrations of cytotoxic chemotherapy drugs (see Figure legends).
Direct immunofluorescence staining was performed using 1-2×105 cells at 106 cells/mL for 30 min at room temperature in PBS containing 0.1% BSA and 5 μg/mL of FITC-conjugated mAb. Cells were thoroughly washed using PBS and centrifugation at 450×g. Cells were resuspended in PBS containing 0.5 μg/mL PI and acquired immediately by a Becton-Dickinson FACScan™ flow cytometry system (BD Biosciences, CA, USA). Positive staining using the mAb-FITC conjugates was determined in comparison to FITC-conjugated isotype control mAb detected using the FL-1 channel (530-nm filter). Indirect immunofluorescent staining was performed using purified mouse antibodies followed by anti-mouse IgG conjugated to Alexa48g detected using the FL-1 channel (530-nm filter). Cell viability was assessed by the exclusion of PI detected using the FL-2 (585-nm filter) or the exclusion of 7-AAD detected using the FL-3 (>650 nm filter). Flow cytometry data was analysed using WinMDI v 2.8 (Scripps Research Institute, CA, USA). Unless otherwise specified, no gating was performed in any of the analysis shown in this paper.
SDS-PAGE was performed as per manufacturer instructions using the Hoefer® Mighty Small II SE 250 electrophoresis system (Amersham Biosciences, N.J., USA) under reducing condition using 12% resolving polyacrylamide gel as per Laemmli (Nature 227: 680-685, 1970). Transfer of polyacrylamide gel onto Hybond-P membrane was carried out as per manufacturer instruction using the TE 22 Mini Tank Transfer Unit (Amersham Biosciences, NJ, USA). Blotting was performed as per standard procedure using 3B9 or anti-PARP mAbs followed by AP-conjugated anti-mouse IgG mAb or anti-actin polyclonal antibody (pAb) followed by AP-conjugated anti-goat IgG mAb. All blots were developed using the ECF™ substrate and scanned using the FluorImager™ 595 (Molecular Dynamics, Amersham Biosciences, NJ, USA) with 488 nm excitation laser and emission collected using 570 nm filter.
Radioligand Binding Study with Anti-La mAb
Sal5 isotype and 3B9 mAb were labelled with 14C by incubating the hybridoma cells (35 million cells) in 35 ml RPMI-1640 containing 10% FCS in the production module of miniPERM bioreactor and 400 ml of RPMI-1640 containing 10% FCS and 250 μCi of D-[U-14C]glucose and 250 μCi of L[U-14C]Leucine in the nutrient module. The bioreactor was incubated in 5% CO2 humidified air at 37° C. on a bottle-rotating device for 5 days. The medium in the production chamber was collected for antibody purification using protein G purification columns as per manufacturer instructions. Radioactivity of purified antibodies (10 μl sample) was counted in UltimaGold™ scintillation liquid (1 ml) for 20 min. using Tri-Carb 3100 n-counter (Packard, regularly calibrated using supplied 14C standards). Protein concentration was determined using BCA Protein Reagent Assay as per manufacturer instructions. The specific radioactivity of 14C-Sal5 and 14C-3B9 was 120.3 and 130.8 dpm/μg, respectively.
Saturation binding study was performed by incubating apoptotic EL4 cells (5×105 cells) at 24 h after treatment with etoposide and cyclophosphamide with increasing concentration of 14C-3B9 in the absence (total) or presence (non specific) of 50-fold molar excess of unlabelled 3B9. After 30 min, cells were washed thoroughly using PBS and radioactivity was measured using β-counter as described above. Specific binding was calculated as the difference between total and non-specific binding and plotted as a function of concentration of 14C-3B9. Competition binding curve was constructed by incubating apoptotic EL4 cells with 14C-3B9 in the presence of increasing concentrations of unlabelled 3B9. Radioactivity was measured as described earlier and plotted as a function of unlabelled 3B9 concentration. Association time course was performed by incubation of apoptotic EL4 cells with 14C-3B9 in the absence or presence of 50-fold molar excess of unlabelled 3B9 for the specified times. Samples were washed and radioactivity was measure and specific binding was plotted as function of time.
EL4 cells, established from a lymphoma induced in a C57BL/6 mouse (Gorer, British Journal of Cancer 4: 372-379, 1950), were used to establish subcutaneous tumour implants in 6-8 weeks old C57BL/6 mice. Mice were housed and treated as per protocols approved by the Animal Ethics Committee at The University of Adelaide. Briefly, 105 EL4 cells were injected subcutaneously in the right flank of each mouse. Once the tumour reached 1 cm diameter, mice were randomly divided into two groups one of which received intraperitoneal injection of etoposide and cyclophosphamide to achieve a dose of 76 mg/kg and 100 mg/kg, respectively (time 0). These two groups (untreated or treated) were used for the studied described below.
Treated mice received a second injection of etoposide and cyclophosphamide at 24 h after the first injection while untreated mice were left untreated. After 24 h (i.e. time point 48 h), all mice were euthanised, whole blood was obtained by cardiac puncture and EL4 tumours were excised from these sacrificed mice. Excised tumours tissue was disrupted to produce a single cell suspension, washed with PBS and used for immunofluorescent staining with 3B9 and PI and flow cytometry analysis as described earlier.
In other studies, treated mice that received the first chemotherapy injection at time 0, received a second injection of etoposide and cyclophosphamide at 24 h and an intravenous injection of specified amount of 14C-3B9 or 14C-Sal5. Untreated mice only received the intravenous injection of 14C-3B9 or 14C-Sal5. All mice were euthanased, whole blood was obtained by cardiac puncture and EL4 tumours as well as other organs were collected for radioactivity measurement. Serum and organs were solubilised using 1 ml of Solvable™ for 2 h at 50° C., decolourised using 100 μl of H2O2 (30%). UltimaGold™ scintillation liquid (1 ml) was added and samples were counted for 10 min. using the β-counter.
Cytofluographic analysis of cultured EL4 thymic lymphoblastic lymphoma cells, which were stained with the DNA binding dye 7-AAD as a test of membrane integrity, indicated that fewer than 10% of the cultured cells were spontaneously apoptotic and did not bind La-specific 3B9 mAb (
After cell permeabilisation, it was found that significantly higher levels of 3B9 bound to the malignant EL4 lymphoma cell line than to its normal murine counterpart cell type of the thymocyte (
La-specific mAb, which was biosynthetically labelled with the radioisotope carbon-14 (14C-3B9), bound to apoptotic EL4 cells after they were treated with cyclophosphamide and etoposide in a specific and saturable manner. The concentration of agent required to reach half-maximal saturation of one million apoptotic cells was 18 nM and maximal binding was ˜7500 femtomole/million apoptotic cells (
Single cell suspensions were prepared from tumour explants of EL4 tumour-bearing mice, which had been treated or not with cytotoxic chemotherapy. As illustrated in
La-Specific mAb Targets EL4 Tumours In Vivo Especially after Cytotoxic Chemotherapy
EL4 tumour-bearing mice were used to demonstrate that 3B9 La-specific mAb targeted a tumour mass in vivo and that the 3B9 targeting was enhanced 48 hours after the mice were treated with cytotoxic chemotherapy. As illustrated graphically in
The biodistribution studies of 14C-3B9 in EL4 tumour-bearing mice were extended to include lower doses of the radiolabelled agent. Again, as shown in
Using a murine tumour model, La-specific in vitro labelling of dead malignant cells and La-specific in vivo targeting of malignant tumours, which were both significantly augmented by the use of cytotoxic chemotherapy, have been described. Hence, it was sought to determine if similar findings applied to human malignant cells in vitro. First, it was found that in comparison to the counterpart normal cell type, La was overexpressed in the Jurkat T cell leukemia line (cf. CD3+ lymphocytes), the U-937 monocytic leukemia line (cf. CD14+ monocytes) and the oropharyngeal squamous cell carcinoma line SSC-25 (cf normal buccal mucosal cells) (
The nuclear structural and molecular changes that accompany malignancy together with additional apoptosis-related changes in the expression levels, processing and translocation of the constituent nuclear proteins suggest that other of these proteins may be suitable targets for this approach. Hence, the criteria that have been developed to characterize targeting of the La antigen for the purpose of radio-imaging and radio-immunotherapy can be applied in order to define other appropriate nuclear target antigens for the application of the present technology (Apomab criteria). In particular, radiosensitising chemotherapy creates new abundant targets in the tumour mass, which were not previously available, and these revealed antigens may be targeted using monoclonal antibodies, which are conjugated to therapeutic radionuclides in order to deliver cytotoxic radiation to the radiosensitised tumour and supporting tissue.
The Apomab criteria used to determine nuclear antigens (Ag) that are particularly suitable for targeting dead tumour cells for diagnostic and therapeutic purposes are:
By applying these criteria in part or in full, antigens can be targeted that produce an enhanced signal to noise ratio for diagnostic imaging and an improved therapeutic ratio for targeted radiation. Although the La targeting data suggest that some of these antigens may be accessible at low levels in untreated tumours, it is found that cytotoxic chemotherapy exposes an abundance of antigen-specific binding sites. Therefore, the combination of cytotoxic radiosensitising chemotherapy or non-cytotoxic radiosensitising drug and the method of RIT will not only produce more effective and safer anti-cancer treatment than either modality (chemotherapy or RIT) alone but will also be considerably more advantageous than other methods of RIT that target pre-existing dead cells.
As an example of how the Apomab criteria may be applied experimentally, monoclonal antibodies specific for other nuclear antigens were tested in a fluorocytometric assay of apoptotic cisplatin-treated Jurkat cells (
Consistent with pre-clinical animal data, further in vitro data are presented to discuss how the method of RIT in combination with radiosensitising cytotoxic chemotherapy may be applied clinically. The data presented in
The scheduling and dose of the component modalities of combination therapy may need to be varied to achieve the optimal combination. In particular, use of full doses of potent radiosensitizing drugs such as gemcitabine to induce cytotoxicity may cause apoptotic cell death in susceptible normal tissues such as bone marrow and the intestinal mucosa. Using the mouse jejunum as a model tissue, Milas and colleagues studied the effects of gemcitabine and showed that the time course of apoptosis was short and that recovery was complete within a 24-36 hour period (Milas L et al. Cancer Res 59, 107-114, 1999). In contrast, changing views about the modes of cell death in carcinomas induced by ionizing radiation or cytotoxic drugs indicate that the time course of cell death in tumours may be extended over a period of days or longer (Brown J M, Attardi L D. Nature Rev Cancer 5, 231-237, 2005). Hence, a window of opportunity may open for the use of combined modality RIT and radiosensitising chemotherapy that minimises harm to normal apoptosis-sensitive tissues while maximising the potential for further radiation-induced cell death to the tumour. In which case, the critical factors that will determine the therapeutic ratio of the RIT will include the relative half-lives of the monoclonal antibody and its conjugated radionuclide.
Combination chemotherapy with the radiosensitising drugs, cisplatin and gemcitabine, produces higher response rates in pancreatic cancer patients than the use of single agent gemcitabine but it does not improve overall survival and is associated with greater toxicity compared with the use of single agent gemcitabine. Thus, despite the higher response rate, combination cisplatin/gemcitabine chemotherapy presumably fails to eradicate systemic metastases, which re-grow to kill the patient. Armed Apomab enables delivery of higher and potentially curative doses of radiation to tumour metastases by taking advantage of the more potent cytotoxic effects and hence anti-tumour properties of the cisplatin/gemcitabine combination. Consequently, the creation of tumour targets (Auto-targeting) may be scaled to the schedule and dose of cytotoxic chemotherapy. In particular, greater targeting of armed Apomab to tumours after combination cisplatin/gemcitabine chemotherapy, results from two major effects, which are shown schematically in Table 4:
The potential significance of the scaling concept is related to the dose-dependent effects that radiation has on both supporting tumour vasculature and the tumour cells themselves. If Apomab RIT were given in conjunction with combination cytotoxic chemotherapy such as cisplatin and gemcitabine then higher in vivo binding to apoptotic/necrotic tumours would occur than if it were given in conjunction with single agent chemotherapy. In which case, it would be expected that higher doses of radiation would be delivered to neighbouring viable tumour cells. For example, if a radiation dose of ≧8-10Gy were delivered to a tumour by combination cisplatin/gemcitabine chemotherapy then apoptosis of tumour endothelial cells may result from release of ceramide (Z Fuks and R Kolesnick. Cancer Cell 8, 89-91, 2005). However, if Apomab RIT delivered a radiation dose below this threshold to the tumour then further radioenhancement may result if ceramide generation were increased, for example, by using an inhibitor of sphingosine kinase I (SKI) or other radiosensitising agents such as inhibitors of VEGF or bFGF. At lower doses of radiation (1.8-3Gy), different anti-tumour mechanisms come into play such as generation of reactive oxygen species, which induce production of the hypoxia-inducible factor-1α (HIF1α). HIF1α protects against tumour endothelial cell apoptosis thus inducing radioresistance but simultaneously sensitises tumour cells to radiation in a p53-dependent manner (Fuks and Kolesnick 2005, supra). Hence, HIF1α inhibitors or inhibitors of VEGF or bFGF may provide additional radiosensitisation when delivering lower doses of radiation (1.8-3Gy) to tumours using Apomab RIT.
Oncomine™ is a cancer-specific database containing microarray data from 962 studies of which 209 were analysed. The database contains 14,177 microarrays from 35 cancer types (information publicly available at the website www.oncomine.org). Several cancer signatures have been deduced from large scale analysis of data held in the database (Hampton, Jama 292(17): 2073, 2004; Rhodes et al., Proc Natl Acad Sci USA 101(25): 9309-14, 2004a; Rhodes et al., Neoplasia 6(1): 1-6, 2004b; Rhodes and Chinnaiyan, Nat Genet 37 Suppl: S31-7, 2005; Rhodes et al., Nat Genet 37(6): 579-83, 2005). 209 studies in the database as described below were analysed in order to investigate certain malignancy signatures, which may provide useful targets for the present invention.
In the catalogue of the database Oncomine™ on www.oncomine.org, the tissue of interest was selected and only analysed data are shown. Studies were viewed using the Advanced Analysis module only for overexpressed genes and enrichment for these genes was achieved using the following options: (1) InterPro for analysis of motifs, (2) Gene Ontogeny (GO) molecular function for the analysis of function and (3) GO cellular component for cellular compartmentation analysis. Two parameters were used to describe the gene sets deduced from the above analysis: (a) Odds Ratio and (b) P-value. Only the groups of interest and genes with a P-value lower than 1E-4 were considered significant for reporting herein.
As shown in Table 5 and Table 6, the ribonucleoprotein (RNP-1) motif was identified, which comprises the RNA recognition motif (RRM), to be at higher odds of being associated with a cancer signature compared to the nucleus as a cellular component. Similarly, the RNA binding gene set, which was enriched as a cellular function, was also at high odds of being associated with a cancer signature. Finally and more importantly, nucleolar and heteronuclear ribonucleoprotein (hnRNP) components appeared to have very high odds as gene sets in association with a cancer signature.
Consequently, components with the RNP-1 motif generally and hnRNP complex specifically are suitable targets for the method of the present invention. This recommendation is justified by (1) association of hnRNP with cancer at the gene expression level (mRNA data reported herein), (2) the relative abundance of this protein and its correlation with cancer and cancer progression (see review Carpenter et al., Biochimica et Biophysica Acta 1765(2): 85-100, 2006), and (3) the reorganisation of the hnRNP network during apoptosis into the HERDS (Biggiogera et al., Biologie Cellulaire 96(8): 603-15. 2004) and the accessibility of the hnRNP network for detection with antibodies. Nucleolar proteins generally and specifically nucleophosmin represent suitable targets for this strategy. This is justified by the data shown in the analysis of the Oncomine™ data base as well as the literature regarding nucleolar function in cancer (Maggi and Weber, Cancer Investigation 23(7): 599-608, 2005) and, in particular, nucleophosmin as putative-proto-oncogene (Grisendi et al., Nature Reviews. Cancer 6(7): 493-505, 2006).
The suppliers of the materials are identified in brackets after each material. Cell culture media, RPMI-1640, DMEM and Ham's F12, and fetal calf serum (FCS) (JRH Biosciences Inc., Lenexa, Kans.); Trypsin-EDTA solution, trypan blue, propidium iodide (PI), bovine serum albumin (BSA), BCIP/NBT premixed substrate solution for alkaline phophatase (AP), hydrocortisone, monodansylcadaverine (MDC) and staurosporine (STS) and mouse anti-human β-tubulin mAb (TUB 2.1) (Sigma-Aldrich Co., St. Louis, Mo.). Hybond-P membrane (PVDF) and protein G purification columns (Amersham Biosciences, Piscataway, N.J.). BCA Protein Reagent Assay (Pierce Biotechnology Inc., Rockford, Ill.). Anti-poly(ADP-ribose) polymerase (PARP) monoclonal antibody (mAb) clone C-2-10 and anti-proliferating cell nuclear antigen (PCNA) mAb clone PC10 (Oncogene Research Products, Cambridge, Mass.). Trichostatin A (TSA), anti-phospho-histone H2AX (Ser139) clone JBW301 biotin-conjugated mAb and anti-human H2A polyclonal antibody (Millipore Inc., Billerica, Mass.). Anti-β fodrin mAb (Chemicon International, Temecula, Calif.). Anti-actin affinity-purified rabbit polyclonal antibody, Fluorescein isothiocyanate (FITC)-conjugated goat anti-rabbit IgG and AP-conjugated goat anti-rabbit IgG antibodies (Rockland, Gilbertsville, Pa.). The anti-La/SS-B 3B9 mAb hybridoma is a murine IgG2a autoantibody, which is crossreactive with human La and which was prepared by Dr M. Bachmann (Oklahoma Medical Research Foundation, Okla., USA), was a kind gift from Dr T. P. Gordon (Department of Immunology, Allergy and Arthritis, Flinders Medical Centre, SA, Australia). The isotype control Sal5 (1D4.5) mAb hybridoma, prepared by Dr L. K. Ashman (Medical Science Building, University of Newcastle, NSW, Australia), was kindly supplied by Dr S. McColl (School of Molecular Biosciences, University of Adelaide, SA, Australia). The mAb were affinity-purified using protein G columns and FITC-conjugates were prepared according to the manufacturer's instructions (Sigma-Aldrich Co., St. Louis, Mo.). Anti-human nucleolin mAb, anti-human nucleophosmin (NPM) mAb, anti-mouse IgG antibody conjugated to Alexa488, streptavidin-Alexa488, streptavidin-PE, 7-amino-(Axis-Shield PoC AS, Norton, Mass.). Etoposide (Pfizer Inc., NY, USA), cyclophosphamide and cisplatin (Bristol-Myers Squibb Company, Princeton, N.J.) and gemcitabine (Eli Lilly, Indianapolis, Ind.) were obtained from the Royal Adelaide Hospital Cytotoxics Pharmacy (Adelaide, SA, Australia).
Suspension cultures of Jurkat and U-937 leukemia cell lines were maintained in RPMI-1640 containing 5% FCS and passaged by splitting at 1:10 every 72 h. Cultures of adherent MDA-MB-231, MCF-7, PC-3, LNCaP and A549 cancer cell lines were maintained in RPMI-1640 containing 5% FCS and passaged every 48-72 h at a 1:4 dilution after detachment with trypsin-EDTA solution. Adherent sub-confluent cultures of the pancreatic adenocarcinoma cell line, PANC-1, were routinely cultured in RPMI-1640 containing 10% FCS and passaged as above. The squamous cell carcinoma cell line, SCC-25, was cultured in a 1:1 mixture of DMEM and Ham's F12 medium supplemented with 400 ng/mL hydrocortisone and 5% FCS and passaged after detachment using trypsin-EDTA solution. Peripheral blood mononuclear cells (PBMC) were isolated from fresh heparinized blood obtained from normal healthy volunteer donors using Lymphoprep separation and cultured overnight in RPMI-1640 containing 5% FCS to separate adherent cells from those remaining in suspension. Cytofluographic analysis indicated that >70% of both suspension and adherent cells were CD3+ and CD14+, respectively. Hence, CD3- and CD14-enriched PBMC preparations will be described as peripheral blood lymphocytes and monocytes, respectively. Clonetics conditioned cultures of primary human cells were maintained according to the manufacturer's instructions (Cambrex Corporation, East Rutherford, N.J.) and included cultures of Human Mammary Epithelial Cells (HMEC), Prostate Epithelial Cells (PrEC) and Normal Human Bronchial Epithelium (NHBE). Finally, buccal cells were isolated from the gum lining of normal healthy volunteer donors as described.
Apoptosis or cell death was induced by adding cytotoxic drugs to culture media at the specified concentrations. In some experiments, cells were starved by serum deprivation. In other experiments, TSA used at the specified concentrations was prepared from 1 mg/mL stock solution in absolute ethanol. Control (untreated) cells had ≧90% viability determined by PI or trypan blue staining (data not shown). Viable cells were fixed and permeabilized by incubating cells at 5×106 cells/mL in 2% w/v paraformaldehyde solution in PBS (150 mM sodium phosphate and 150 sodium chloride, pH 7.2) for 10 min. followed by 1:10 dilution in absolute methanol (at −20° C.) for 1-3 min. before a final wash with PBS.
Indirect immunofluorescence staining was performed using purified mouse antibodies at 5 μg/mL for 30 min. at room temperature (RT) in PBS followed by Alexa488-conjugated anti-mouse IgG at 2 μg/mL for 30 min. at RT in PBS. Fluorescence was detected using the FL-1 channel (530 nm filter). Cell viability was assessed by the exclusion of PI (0.5 μg/mL) and detected using the FL-2 channel (585 nm filter) or by the exclusion of 7-AAD (2 μg/mL for 15 min. at RT) and detected using the FL-3 channel (>650 nm filter), Staining for γH2AX was performed using 0.2 μg/mL of anti-γH2AX-biotin for 30 min. at RT followed by 2 μg/mL of streptavidin-PE or streptavidin-Alexa488. Staining of polyclonal antibodies (anti-actin or anti-H2A) was performed using 5 μg/mL of antibody solution for 30 min. at RT. Control incubations were performed using protein G purified rabbit IgG from normal rabbit serum (IMVS, SA, Australia). Cells were washed then incubated (30 min. at RT) with 2 μg/mL of FITC-conjugated anti-rabbit IgG antibody, which was detected using the FL-1 channel. Samples were acquired immediately by a Becton-Dickinson FACScan™ flow cytometry system (BD Biosciences, San Jose, Calif.). Acquisition was standardized to 10,000 events or in some cases standardized to a set time for acquisition (in seconds) to allow comparison of cell counts in different incubations. Flow cytometry data were analyzed using WinMDI v2.8 (Scripps Research Institute, La Jolla, Calif.). Unless otherwise specified, no gating was performed in any of the reported analyses. Specific binding of antibodies was calculated as the difference in mean fluorescence intensities (MFI) between the test antibody and the control isotype antibody and expressed as the Net MFI±standard error of the mean (SEM), which was calculated from replicate incubations (n>2).
Cell lysates were prepared in SDS lysis solution (2% w/v SDS, 10% v/v glycerol and 62.5 mM Tris-HCl) and protein concentration was determined using BCA protein reagent assay kit according to the manufacturer's instructions. Bromophenol blue (0.05% w/v) and β-mercaptoethanol (5% v/v) were added to lysates after BCA assay measurement. SDS-PAGE was performed according to the manufacturer's instructions with the Hoefer Mighty Small II SE 250 electrophoresis system (Amersham Biosciences, Piscataway, N.J.) under reducing conditions using 12% resolving polyacrylamide gel as per Laemmli's method. The transfer of the polyacrylamide gel to Hybond-P membrane was carried out according to the manufacturer's instructions using the TE 22 Mini Tank Transfer Unit (Amersham Biosciences, Piscataway, N.J.). Immunoblotting was done using standard methods in which staining with 3B9 was followed by staining with AP-conjugated anti-mouse IgG mAb (Jackson ImmunoResearch Laboratories Inc., West Grove, Pa.) or anti-actin (N-20) affinity purified goat polyclonal antibody (Santa Cruz Biotechnology Inc., Santa Cruz, Calif.) followed by AP-conjugated anti-goat IgG mAb (Jackson ImmunoResearch). Some blots were developed using the BCIP/NBT premixed solution as specified by the manufacturer and analyzed using GelPro Analyzer v3.1 (Media Cybernetics Inc., Silver Spring, Md.).
Other blots were developed using the ECF™ substrate (Amersham Biosciences, Piscataway, N.J.) and scanned using the FluorImager™ 595 (Molecular Dynamics, Amersham Biosciences, Piscataway, N.J.) with a 488 nm excitation laser and the emissions were collected using a 570 nm filter.
Transglutaminase 2 (TG2)-mediated protein-protein crosslinking in apoptotic cells was investigated using a modification of a previously described method. Briefly, cells were resuspended at 1×106 cells/mL in PBS containing 1% Triton X-100, 0.2 μg/mL sulforhodamine 101 and 0.1 μM SytoxGreen. Samples were vortexed and incubated for 5 min. before analysis by flow cytometry where fluorescence from Sytox Green and sulforhodamine were detected using FL-1 and FL-3, respectively. The degree of crosslinking in apoptotic cells was calculated as the ratio of the MFI of sulforhodamine staining in apoptotic cells to the MFI in control cells (protein crosslinking ratio). In other experiments, cells were incubated with PBS or 1% Triton X-100 in PBS for 10 min. at RT with intermittent vortexing.
To test inhibition of protein crosslinking, cultured cells were incubated with increasing concentrations of the competitive TG2inhibitor, monodansylcadaverine (MDC). MDC was dissolved in DMSO at 25 mM and then diluted in culture media before it was added to cell cultures at the specified concentrations for the specified duration. Incorporation of the TG2 substrate, biotinylated cadaverine, in cellular proteins was used as an index of TG2 activity. Cells were incubated with increasing concentrations of cisplatin with or without 100 μM cadaverine-biotin (from 25 mM stock solution in DMSO). Cells were collected after 48 h, washed extensively with PBS and incubated with streptavidin-Alexa488 for cytofluographic analysis. In similar assays, cadaverine-biotin labelled cells were lysed for SDS-PAGE with or without prior immunoprecipitation using 3B9 mAb. PAGE gels were transferred to PVDF membranes and probed using streptavidin-AP to visualise both the total pool of TG2 substrates and 3B9-reactive TG2 substrates.
Cells were stained using immunofluorescence methods described above and then spotted onto glass slides using the cytospin method. The prepared slides were mounted with coverslips using non-fluorescence mounting medium (Dako, Carpinteria, Calif.). Slides were analyzed using a BioRad Olympus Confocal microscope with appropriate filters and under constant conditions of laser voltage, iris aperture and photomultiplier tube amplification.
Jurkat cells were incubated in the presence or absence of 20 μg/mL cisplatin and pelleted 3 h after treatment to prepare soluble nuclear and chromatin fractions as described. Samples of these fractions were fractionated using 12% SDS-PAGE for immunoblotting as described above. Membranes were probed with 1 μg/mL 3B9, 2 μg/mL anti-H2A antibodies or 0.2 μg/mL anti-γH2AX-biotin followed by the appropriate AP-conjugated secondary antibodies or strepatividin-AP. The presence of H2A in chromatin and not soluble fractions was used to assess the quality of preparation of the chromatin fractions.
Chamber slides were seeded with PANC-1 cells and incubated overnight in RPMI-1640 containing 10% FCS before replacement with medium containing 20 μg/mL cisplatin alone or in combination with TSA. After 3 h, cells were fixed and permeabilized using paraformaldehyde and methanol as described above Cells were washed and blocked with 5% BSA solution in PBS then stained with 10 μm/mL 339 followed by 2 μg/mL Alexa488-conjugated anti-mouse IgG antibody. Cells were washed and incubated with 0.2 μg/mL anti-γH2AX-biotin followed by 2 μg/mL streptavidin-PE. Finally, cells were washed and coverslips were mounted using non-fluorescent mounting media (Dako, Glostrup, Denmark). Alexa488 and PE were excited using a 488 nm laser and fluorescence was detected using filters 1 and 2, respectively, of an Olympus fluorescence microscope. Samples stained separately with 3B9 or γH2AX showed that there was no fluorescence bleeding between the two different filters using the specified fluorophores (data not shown).
Oncomine is a database of microarray data, which holds data from 962 studies of which 209 were analyzed. The database contains 14,177 microarrays from 35 cancer types (information publicly available at the website www.oncomine.org). Several cancer signatures have been deduced from large scale analysis of data in the database (24-28). We analyzed the 209 studies using the Advanced Analysis module limiting results to overexpressed genes only and gene enrichment was selected using the following options: (1) InterPro for analysis of motifs in the overexpresed genes, (2) Gene Ontogeny (GO) molecular function for analysis of functions of overexpressed genes, and (3) GO cellular component for cellular compartmentation of the overexpressed genes. Two paramaters were used to describe the gene sets deduced from the above analysis (a) Odds Ratio and (b) P-value, which were provided by the database.
Statistical comparisons were performed using GraphPad Prism v4 (GraphPad Software, San Diego, Calif.). Generally, two-way analysis of variance (ANOVA) was used to deduce significant differences among the results. The Bonferroni post-test comparison was used to report P values. P values are denoted as: *, P<0.05; **, P<0.01; ***, P<0.001.
As
Synchronisation of Jurkat cells by double-thymidine block demonstrates that maximal binding of Apomab, and by inference maximal expression of La, occurs during S phase of the cell cycle (
Cytofluographic analysis of etoposide-treated Jurkat cells showed a time-dependent loss of cell membrane integrity, which was measured by binding of propidium iodide (PI) to intracellular nucleic acids. Despite the loss of cell membrane integrity, dead and/or dying cells did not accumulate Sal5 mAb, which is an isotype control antibody of irrelevant specificity (upper panel,
Nonetheless, significant differences in binding levels of the mAb specific for the different intracellular antigens were observed after induction of Jurkat cell apoptosis with the DNA-damaging drug, cisplatin. Antigen-specific mean fluorescence intensity (MFI) of cisplatin-treated Jurkat cells was compared with the MFI of control untreated Jurkat cells, which were fixed and permeabilized (
Further evidence for induction of 3B9 binding by DNA-damaging agents was obtained by comparing serum-deprivation with cisplatin-treatment of various malignant cell types. In MCF-7, MDA-MB-231, A549 and PC-3 cancer cell lines, significantly greater 3B9-specific binding to the dead malignant cells was observed after use of the DNA-damaging agent (
As
Further evidence for the involvement of La in the DNA-damage response was obtained using chemotherapy-resistant PANC-1 cells. Neither gemcitabine (
As illustrated in
The same dose of cisplatin is used to treat Jurkat cells that are subsequently permeabilised and fixed and stained with mAb specific for a number of nuclear antigens (
Resistance of apoptotic cells to the non-ionic detergent, Triton X-100, has been reported and correlates with the activity of tissue transglutaminase or transglutaminase 2 (TG2), which mediates protein-protein crosslinking. It was found that during apoptosis, the proportion of 7-AAD+ cells and the level of 3B9 binding to these cells were comparable irrespective of Triton X-100 treatment (
Next, it was hypothesized that inhibition of TG2 activity reduces 3B9 binding to apoptotic cells because of reduced protein-protein crosslinking. First, the effect of increasing doses of cisplatin on the activity of TG2 in Jurkat cells was investigated using the TG2 substrate cadaverine-biotin. Incorporation of cadaverine-biotin into Jurkat cells showed a dose-dependent relationship to cisplatin concentration (
Using etoposide or cisplatin, Jurkat cells were induced to undergo apoptosis in the presence of 3B9 or its Sal5 isotype control mAb. 3B9 binding to apoptotic Jurkat cells was detectable even after stripping of the Jurkat cells with Triton X-100, which suggests that the protein cross-linking process in apoptotic cells includes the cross-linking of bound antigen-specific mAb (
The EL4 murine T-lymphoblastic lymphoma cell line was obtained from American Type Cell Culture (TIB-39) and murine thymocytes were freshly prepared from 6-8 week old C57BL/6 mice. Cells were routinely cultured in RPMI-1640 containing 5% FCS (JRH Biosciences Inc. Lenexa. KS) and passaged every 48-72 h at 1:4 dilution. 3B9 and the relevant control (Sal5) were prepared as described previously (first paper). Fluorescein isothiocyanate (FITC) conjugated of these agents was prepared as described by manufacturer's instructions (Sigma-Aldrich Co., St. Louis, Mo.).
Apoptosis in cultures was induced by adding 20 μg/mL etoposide (Pfizer Inc., NY, USA) and 20 μg/mL cyclophosphamide (Bristol-Myers Squibb Company, Princeton, N.J.) to the culture media. Data presented here from control (untreated cells) originated from samples with higher than 90% viability as determined by PI or trypan blue (Sigma-Aldrich Co., St. Louis, Mo.) staining (data not shown). Permeabilization of viable cells was performed by 10 min. incubation in 2% w/v paraformaldehyde solution in PBS (150 mM sodium phosphate and 150 mM sodium chloride, pH 7.2) at 5×106 cells/mL, which was diluted 1:10 with −20° C.-cold absolute methanol (1-3 min.) before washing with PBS.
Direct immunofluorescence staining was performed using 1-2×105 cells at 106 cells/mL for 30 min. at room temperature (RT) in PBS containing 0.1% bovine serum albumin (BSA, Sigma-Aldrich Co., St. Louis, Mo.) and 5 μg/mL of FITC-conjugated 3B9 or FITC-conjugated Sal5 isotype control mAb. Indirect immunofluorescence staining was performed using purified mouse antibodies (5 μg/mL for 30 min. at RT in PBS) followed by anti-mouse IgG conjugated to Alexa488 (Invitrogen, Carlsbad, Calif.) (2 μg/mL for 30 min. at RT in PBS) and detected using the FL-1 channel (530-nm filter). Cell viability was assessed by the exclusion of PI (0.5 μg/mL) and detected using the FL-2 channel (585-nm filter) or by the exclusion of 7-AAD (Invitrogen, Carlsbad, Calif.) (2 μg/mL for 15 min. at RT) and detected using the FL-3 channel (>650 nm filter). Samples were acquired immediately by Becton-Dickinson FACScan™ flow cytometry system (BD Biosciences, San Jose, Calif.). Acquisition was standardized to 10,000 events. Flow cytometry data was analyzed using WinMDI v 2.8 (Scripps Research Institute, La Jolla, Calif.). Unless otherwise specified, no gating was performed in any of the reported analyses. Specific binding of antibodies was calculated as the difference in the mean fluorescent intensity (MFI) from the test antibodies and that from control isotype antibody and was expressed as the Net MFI±standard error of the mean (SEM) calculated from replicate incubations (n>2).
Cell lysates were prepared in SDS lysis solution (2% w/v SDS, 10% v/v glycerol and 62.5 mM Tris-HCl) and protein concentration was determined using BCA protein reagent assay kit according to the manufacturer's instructions (Pierce Biotechnology Inc., Rockford, Ill.). Bromophenol blue (0.05% w/v) and (3-mercaptoethanol (5% v/v) (Sigma-Aldrich Co., St. Louis, Mo.) were added to lysates after BCA assay measurement. An amount of 12 μg of lysate was added to each lane for SDS-PAGE. SDS-PAGE was performed according to the manufacturer's instructions with the Hoefer® Mighty Small II SE 250 electrophoresis system (Amersham Biosciences, Piscataway, N.J.) under reducing condition using 12% resolving polyacrylamide gel as per Laemmli's method. The transfer of the polyacrylamide gel to Hybond-P membrane was carried out according to the manufacturer's instructions using the TE 22 Mini Tank Transfer Unit (Amersham Biosciences, Piscataway, N.J.). Immunoblotting was done using standard methods in which staining with 3B9 was followed by staining with alkaline phosphatase (AP)-conjugated anti-mouse IgG mAb (Jackson ImmunoResearch Laboratories, Inc., West Grove, Pa.). Blots were developed using the BCIP/NBT premixed solution as specified by manufacturer (Sigma-Aldrich Co., St. Louis, Mo.) and analyzed using GelPro Analyzer v3.1 (Media Cybernetics Inc., Silver Spring, Md.).
3B9 and matched control were labelled with 14C by incubating the hybridoma cells (35 million cells) in 35 mL RPMI-1640 containing 5% FCS in the production module of miniPERM bioreactor (Vivascience GmbH, Hannover, Germany) and 400 mL of RPMI-1640 containing 5% FCS and 250 μCi of D-[U-14C]glucose and 250 μCi of L[U-14C]leucine (Amersham Biosciences, Piscataway, N.J.) in the nutrient module. The bioreactor was incubated in 5% CO2 humidified air at 37° C. on a bottle-rotating device for 5 days. The medium in the production chamber was collected for purification using Protein G purification columns. Radioactivity of purified antibodies (10 μL sample) was counted in UltimaGold™ scintillation liquid (1 mL) for 20 min using Packard Tri-Carb 3100 β-counter (PerkinElmer Inc., Wellesley, Mass.) regularly calibrated using supplied 14C standards. Protein concentration was determined using BCA protein reagent assay. The specific radioactivity of 14C-control and 14C-3B9 was 120.3 and 130.8 dpm/μs, respectively.
Saturation binding assays were performed by incubating apoptotic EL4 cells (5×105 cells) after 48 h treatment with etoposide and cyclophosphamide with increasing concentrations of 14C-3B9 in the presence (to measure non-specific binding) or absence (to measure total binding) of a 50-fold molar excess of unlabelled 3B9. After 30 min., cells were washed thoroughly using PBS and radioactivity was measured using the □-counter as described above. Specific binding was calculated as the difference between total and non-specific binding and plotted as a function of the concentration of 14C-3B9. Competition binding assays were carried out by incubating apoptotic EL4 cells with 100 nM 14C-3B9 in the presence of increasing concentrations of unlabelled 3B9. Radioactivity was measured as described above and plotted as a function of unlabelled 3B9 concentration. Association assays were performed by incubation of apoptotic EL4 cells with 100 nM 14C-3B9 in the presence or absence of a 50-fold molar excess of unlabelled 3B9 for the specified times. Samples were washed, radioactivity was measured and specific binding was plotted as function of time. Dissociation assays were performed after incubation of apoptotic EL4 cells with 100 nM 14C-3B9 in the absence or presence of 50-fold molar excess of unlabelled 3B9 for 30 min. at RT. Cells were washed, incubated at 37° C. in PBS and samples were removed at the specified times. These samples were washed with PBS, radioactivity was measured and specific binding was plotted as function of time.
The EL4 thymic lymphoblastic lymphoma is a robust model of apoptosis, which is induced by the cytotoxic drugs, cyclophosphamide and etoposide (14). Subcutaneous EL4 tumour implants were established in 6-8 week old syngeneic C57BL/6 mice where 106 EL4 cells were injected subcutaneously in the right flank of each mouse. Mice were housed and treated as per protocols approved by the Animal Ethics Committee at The University of Adelaide and the Animal Ethics Committee at the Institute of Medical and Veterinary Sciences (IMVS). Once the tumour reached 1 cm diameter, mice were randomly divided into control or treatment groups.
Treatment comprised intraperitoneal injections of cytotoxic chemotherapy given in one of the following five regimens of reducing dose intensity. The respective cyclophosphamide and etoposide doses are indicated and are mg/kg. (i) full dose as published: 100, 76 at 0 h and 24 h; (ii) half dose 2d: 50, 38 at 0 h and 24 h; (iii) half dose 1 d: 50, 38 at 0 h; (iv) quarter dose 2d: 25, 19 at 0 h and 24 h; (v) quarter dose 1 d: 25, 19 at 0 h.
Control and chemotherapy-treated mice bearing EL4 tumours were euthanized 48 h after treatment and tumours were excised. Excised tumour tissue was disrupted by incubation in RPMI-1640 containing 2 mg/mL collagenase (Sigma-Aldrich Co., St. Louis, Mo.) for 30 min. at 37° C. with constant shaking. Single cell suspensions were washed with PBS and used for immunofluorescent staining with 3B9-FITC or Sal-FITC and PI and flow cytometry analysis as described earlier.
14C-3B9 biodistribution in EL4 Tumour Bearing Mice
Control and chemotherapy treated mice received an intravenous injection of 14C-3B9 or 14C-Sal5 (control) at time 0. After 48 h, mice were euthanized, whole blood was collected by cardiac puncture, and EL4 tumours and other tissues were collected for radioactivity measurement. Serum and body tissues were solubilized using 1 mL Solvable™ (PerkinElmer Inc., Wellesley, Mass.) for 2 h at 50° C., and then decolorized using 100 μL H2O2 (30%) (Sigma-Aldrich Co., St. Louis, Mo.). UltimaGold™ scintillation liquid (1 mL) was added and samples were counted for 10 min. using the β-counter.
Protein G purified 3B9 or Sal5 mAb were mixed at 2.5 mg/mL in 0.1M sodium bicarbonate and 0.1M sodium phosphate buffer (pH8.5) with 50-fold molar excess of DOTA-NHS-Ester (Macrocyclics, Dallas, Tex.) dissolved in DMSO (Sigma-Aldrich Co., St. Louis, Mo.). DMSO represented <10% of the final reaction, which was incubated for 2 h at 23° C. with constant vigorous shaking. DOTA-NHS-Ester was added at a 50-fold molar excess to the antibody as this ratio was found to minimize inactivation of 3B9 and showed favorable in vivo biodistribution compared to Sal5 conjugated at the same ratio and to 3B9 conjugated at higher ratios (data not shown). Addition of 1.5M Tris-HCl (pH8.8) at a final dilution of 1:10 was used to stop the reaction, which was loaded onto a 100 kDa-cutoff microconcentrator (Millipore, Billerica, Mass.). Reactions were buffer-exchanged using 5×500 μL washes of PBS. The concentration of IgG was measured using a BCA protein assay kit and the concentration of conjugated DOTA was measured using a modification of a published Cu:Arsenazo(III) assay. The ligand/protein (LIP) ratio of 7.5 was calculated as the ratio of the concentrations (μM) of DOTA-immunoconjugates to IgG. The reaction was stored at 4° C. before radiolabeling.
Purified DOTA-immunoconjugate solutions were concentrated and buffer-exchanged into metal free 0.2M ammonium acetate buffer (pH5.5) (Sigma-Aldrich Co., St. Louis, Mo.) containing 6 mg/mL ascorbic acid (Sigma-Aldrich Co., St. Louis, Mo.). Indium-111 chloride (PerkinElmer Inc., Wellesley, Mass.) was diluted in the same buffer (5 mCi/mL; 185 MBq/mL) and mixed with DOTA immunoconjugates (10 mg/mL). Radiolabeling reactions were incubated at 37° C. for 2 h then mixed with an equal volume of 0.2M ammonium acetate buffer (pH8) containing 5 mM EDTA to quench free and loosely bond radionuclide. Quenched reactions were loaded onto 100 kDa-cutoff microconcentrators and purified by three washes of 5004 endotoxin free PBS. The incorporation of 111In in the purified reactions was determined using instant thin layer chromatography (ITLC) which was performed using ITLC-SG strips (Pall Corporation, East Hills, N.Y.) in 0.2M ammonium acetate solution (pH 8) containing 5 mM EDTA as mobile phase. Briefly, aliquots (2 μL) of purified reactions and free 111In in 0.2M ammonium acetate and 5 mM EDTA were used for ITLC in the mobile phase and the origin and solvent front halves of strips were counted using a Cobra 5010 gamma counter (PerkinElmer Inc., Wellesley, Mass.) normalized for 111In counting using a 100-350 keV counting window. While 99% of radioactivity on the ITLC-SG strip was at the solvent front when ITLC was performed using 111InCl3 solution, 99% of radioactivity in the DOTA-conjugates remained at the origin indicating the complete incorporation of 111In in the DOTA-3B9 conjugate (data not shown). 1 At 0 h, 111In-DOTA-3B9 (72 μg in 100 μL of PBS) was given by intravenous injection to EL4 tumour-bearing mice, which were left untreated or treated with cytotoxic chemotherapy as described above. Mice were euthanized at selected time points, blood was collected by cardiac puncture, and tumours and organs were collected. Blood and organs were weighed and placed in gamma-counter tubes and radioactivity was measured using normalized Cobra5010 gamma counter. Radioactivity in organs was normalized to the weight of the organs and accumulation was calculated as the percentage of radioactivity per gram in the organs to the radioactivity of the injected dose of 111In-DOTA-3B9 at time 0 (% ID/g). Time activity curves for blood and tumours were constructed using GraphPad Prism v.4 (GraphPad Software, San Diego, Calif.) for each treatment group where accumulation % ID/g (±SEM, n=5) plotted as a function of time. Curves were fitted to one-phase exponential decay for blood and one-phase exponential association for tumours and the half-life (t1/2) was provided from the fitted models. In the case of tumour accumulation, the fitted association model also provided a value for maximal accumulation at saturation together with the corresponding standard error of this measurement, which we report as % ID/g+SEM at saturation. Data points did not deviate from the fitted models as judged by runs test performed using the fitting software and the regression value of the fitted model was provided.
Statistical comparisons were preformed using GraphPad Prism. Two-way analysis of variances (2-way ANOVA) was used to deduce significant differences in the results. The Bonferroni post-test in the 2-way ANOVA function in GraphPad prism was used to report P values. P values less than 0.05 were considered significant where one, two and three asterisks denote P values less than 0.05, 0.01 and 0.001, respectively.
Cytofluographic analysis of cultured EL4 lymphoma cells, which were stained with the DNA binding dye 7-AAD as a test of membrane integrity, indicated that although <10% of the cultured cells demonstrated evidence of spontaneous cell death, these dead cells did not bind La-specific mAb 3B9 (
Next, biosynthetically labelled 3B9 mAb was used to further characterize the binding of La-specific mAb to dead EL4 cells, which were killed with cytotoxic drugs. It was found that 14C-3B9 bound dead EL4 cells in a specific and saturable manner. The concentration of 14C-3B9 required to reach half-maximal saturation was 18 nM and maximal binding was ˜7500 femtomole/million dead cells (
The in vitro findings depicted in
3B9 Targets EL4 Tumours In Vivo Especially after Cytotoxic Chemotherapy
The biodistribution of La-specific mAb was studied in the EL4 lymphoma model using intrinsically or extrinsically labelled 3B9 mAb. First, biosynthetically labelled 14C-3B9 mAb was used to demonstrate that tumour accumulation of 3B9 mAb was an inherent property of its antigen-binding activity. EL4 tumour-bearing mice were treated with the full dose schedule of cyclophosphamide and etoposide and simultaneously administered 100 μg each of either 14C-3B9 or 14C-Sal5 isotype control mAb before analysis of the mice after 48 hours. The 14C-Sal5 mAb did not accumulate significantly in any organ or tissue including the tumour. In contrast and compared with all other organs, we found that 14C-3B9 accumulated significantly in serum and in the tumour (P<0.001). Moreover, after the mice were treated with cytotoxic chemotherapy, only the tumours accumulated significantly more 14C-3B9 (P<0.001) (data not shown).
In the second series of experiments, 3B9 conjugated to a metal chelator, DOTA, was radiolabelled with 111In and used to investigate the biodistribution and pharmacokinetics in EL4 tumour-bearing mice before and after chemotherapy treatment (
The specificity of 111In-DOTA-3B9 towards the dying tumours was expressed as the ratio of tumour accumulation to that in normal organs (tumour/organ ratio,
A biotinylated form of cadaverine, which is a polyamine TG2 substrate and which consequently becomes covalently bound to other TG2 substrates, is used to identify protein targets of cross-linking during apoptosis. As shown in
Two studies were performed on patient material to indicate that Apomab binding was augmented by DNA-damaging cytotoxic chemotherapy. In the first study, primary ALL blasts from a chemonaïve patient were treated in vitro with cytotoxic drugs and then analysed (
To purify primary ALL blasts for further analyses, Ficoll gradient separation was performed using a 10 mL peripheral blood sample from a newly diagnosed and untreated ALL patient. The buffy coat was collected and washed with culture medium before incubation for 10 min in red cell lysis buffer. Cells were washed, aliquots were removed for immediate analysis while other aliquots were incubated or not in different concentrations of cytotoxic drugs singly or in combination. At 24 h, 48 h, and 72 h after treatment was initiated in vitro, ALL blasts were stained with 10 μg/mL Sal5 control or Apomab then with 2 μg/mL Alexa488-conjugated anti-mouse IgG. Cells were washed and incubated with 2 μg/mL 7-AAD then analysed by flow cytometry immediately.
The level of Apomab binding to permeabilised primary ALL blasts (inset,
Analysis In Vitro of Circulating Small Lung Cancer Cells of a Patient Treated with Cytotoxic Drugs
Anti-La antibody binding to circulating tumour cells in peripheral blood of a 73-year-old male patient, GP, who had extensive-stage SCLC was studied. The patient, GP, who had not previously been treated for his cancer, was administered cytotoxic chemotherapy using carboplatin at AUC 5 on day 1 together with etoposide 120 mg/m2 on days 1, 2 and 3. Heparinised peripheral blood samples were drawn from the patient before chemotherapy (0 h) and 24, 48 and 72 hours after initiation of chemotherapy. To demonstrate that GP's blood contained circulating tumour cells (CTC), his blood was enriched before and after cytotoxic drug treatment for BerEP4-expressing cells, which were present minimally if at all in the peripheral blood of a normal healthy volunteer (control) (
Although the laboratory findings were not correlated with a formal radiological evaluation of overall tumour response to chemotherapy, GP did have a palpable and painful sternal mass before cytotoxic chemotherapy, which became markedly less painful and shrunk significantly in size within two weeks of cytotoxic chemotherapy administration.
In conclusion, these results using patient tumour material indicate that anti-La antibody identifies malignant cells that have died as the result of cytotoxic drug administration and, hence, this antibody may be useful for predicting early chemotherapy responses in cancer patients.
Apoptotic changes after intrinsic pathway activation took longer than after extrinsic pathway activation. During activation of the intrinsic pathway by cisplatin or γ-radiation, evidence of DNA damage was observed at the early 5 h time point in permeabilised cells by γ-phosphorylation of H2AX and, simultaneously, by significantly increased antibody binding, which reflects increased expression of the La target antigen (
In contrast, cells that were overgrown in vitro (
Further analysis indicated differences in the course of apoptosis after γ-radiation visa vis cisplatin treatment (
After Fas ligation, similar considerations applied to activation of caspase-3. As cells turned into apobodies, caspase-3 was activated simultaneously. Caspase activation indicated that cells were being dismantled into apobodies and the caspase-mediated processes likely included DNA degradation. Hence, the creation of simultaneous DSB seemed to be responsible for the striking induction of γH2AX foci and the concomitant induction of La. Activated caspase-3 activation persisted in cells as they converted to apobodies. On the other hand, the γH2AX and La induction occurred initially and transiently in all cells, and so appeared to be a process that was executed in response to the death stimulus applied to all cells and then was complete (
In confirmation that cisplatin treatment and γ-radiation of Jurkat cells induces expression of La antigen, immunoblots of cell lysates prepared shortly after apoptosis induction but before loss of cell membrane integrity were probed with anti-La antibodies or anti-actin antibodies as a loading control (
To show that anti-La antibody bound a variety of other dead human malignant cell lines after cytotoxic treatment, Apomab or its Sal5 isotype control mAb was used to stain malignant cells after treatment with the pan-tyrosine kinase inhibitor (STS), the topoisomerase II inhibitor, etoposide, or the tubule depolymerising agent, vincristine (
In vivo studies were performed to quantify dead cells in EL4 tumours before and after CE chemotherapy, and to measure anti-La antibody uptake by these tumours. To provide evidence in vivo of induction of the La antigen by DNA-damaging chemotherapy, the relationship between tumour anti-La antibody uptake and the percentage of dead cells within tumours were examined.
Anti-La antibody uptake by control tumours was compared with tumour anti-La antibody uptake after CE chemotherapy to determine if it exceeded the level expected if it were only proportionate to the tumour content of dead cells.
C57BL/6 mice bearing EL4 tumours were left untreated (n=3) or treated by intraperitoneal injection (IPI) of 19.5 mg/kg etoposide and 25 mg/kg of cyclophosphamide (n=3). Mice were killed at specified time points, tumours were excised, minced into pieces <10 mm3 using scissors, and 0.1 g of minced tumour weighed and placed in 10 mL 2 mg/mL solution of collagenase Type 1 in HBSS containing 2.5 mM Ca2+. Solutions were incubated at 37° C. with constant rotation for 1 h. Digested tumour cell suspensions were passed sequentially through syringes with 19 G, 23 G then 25 G needles. Suspensions were centrifuged at 2000 rpm for 5 min and pellets were washed with 10 mL HBSS. Washed pellets were resuspended in 1 mL HBSS and 100 μL aliquots were stained for 10 min at room temperature (RT) in duplicate with 2 μg/mL 7-AAD. Samples were analysed using flow cytometry for the percentage of cells that bound 7-AAD to measure the percentage of dead cells (7-AAD+).
C57BL/6 mice bearing EL4 tumours were left untreated (n=5) or treated with chemotherapy (n=5) as described above. All mice were also injected intravenously with 111In-Apomab. Mice were killed at specified time points, tumours were excised, weighed, and placed in gamma counting tubes to measure radioactivity. Measured radioactivity was normalised to tumour weight (cpm/g) and accumulation was calculated as the percentage of weight-normalised radioactivity counts to total radioactivity counts of injected dose at time 0 h (% cpm/g in tumour/cpm of injected 111In-Apomab at time 0 h).
In comparison with untreated control mice (
To demonstrate this finding more explicitly, Apomab binding to dead tumour cells was related directly to the tumour content of dead cells at each time point (
In conjunction with the data showing therapeutic efficacy of La-directed monoRIT, at least two significant inferences may be drawn from these observations:
Furthermore, cytotoxic radiosensitising drugs such as cisplatin, the antimetabolites gemcitabine and 5-fluorouracil, and the taxanes, will augment the potency of La-directed radioimmunotherapy (RIT) by lowering the threshold for tumour cell death. Therefore, it would be expected that appropriately scheduled administration of a cytotoxic radiosensitising drug and La-directed RIT would lower the effective dose of RIT required for tumour cell kill.
Other than ionising radiation, the radiomimetic drug, cisplatin, topoisomerase inhibitors, DNA-intercalating agents, which are all antineoplastic treatments well known to induce double-stranded DNA breaks (DSB) and some which have been shown to augment Apomab binding to apoptotic tumour cells in vitro, newer agents induce DSB via novel mechanisms of action. For example, PARP inhibitors induce DSB and sensitise to apoptosis those tumour cells that lack DNA repair mechanisms based homologous recombination (HR) such as BRCA nullizygous tumour cells, or tumour cells with features of ‘BRCAness’ (N Turner et al. Nat Rev Cancer 4, 1-6, 2004) because HR is required to repair endogenous DNA damage (HE Bryant et al. Nature 434, 913-917, 2005; H Farmer et al. Nature 434, 917-921, 2005). The antimetabolite and masked DNA chain terminator, gemcitabine, induces few DSB unless the S-phase checkpoint is abrogated by a class of drug known as CHK1/2 inhibitors when DSB become greatly increased and apoptosis ensues (G McArthur et al. J Clin Oncol 24, 3045a, 2006; MA Morgan et al. Cancer Res 65, 6835-6842, 2005). Similar effects were exerted by CHK1/2 inhibitors after ionising radiation induced G2 and S checkpoints (J Falck et al. Nature 410, 842-847, 2001; H Zhao et al. PNAS 99, 14795-14800, 2002).
LnCap cells (5×106 cells) prepared in 50:50 PBS:matrigel were injected in the right flanks of 6-8 weeks old Balb/c female nude mice. When tumours reached 120 cm3 in volume mice were randomly divided into 6 groups of 5-10 mice each (tumour volumes were not significantly different before treatment) (
Chemo: 50 mg/kg gem and 1 mg/kg cis on day 1, 50 mg/kg gem on day 4, 50 mg/kg gem and 1 mg/kg cis on day 7 and 50 mg/kg gem on day 10
Chemo->RIT: 50 mg/kg gem and 1 mg/kg cis on day 1, 50 mg/kg gem on day 4, 50 mg/kg gem and 1 mg/kg cis on day 7, RIT on day 8 and 50 mg/kg gem on day 10
Chemo->RIT: 50 mg/kg gem and 1 mg/kg cis on day 1, RIT on day 2, 50 mg/kg gem on day 4 and 50 mg/kg gem and 1 mg/kg cis on day 8
Chemo+RIT: 25 mg/kg gem and 0.5 mg/kg cis and RIT on day 1, 25 mg/kg gem and RIT on day 4 and 25 mg/kg gem and 0.5 mg/kg cis on day 7
Growth curves were fitted to exponential growth curve (R2>0.90) using GraphPad Prism. Doubling time and tumour growth to 50% were provided by the fitted curve.
PANC-1 cells (5×106 cells) prepared in 50:50 PBS:matrigel were injected in the right flanks of 6-8 weeks old Balb/c female nude mice. When tumours reached 50 cm3 in volume mice were randomly divided into 4 groups of 5 mice each (tumour volumes were not significantly different before treatment) (
Group 3: Chemo, 50 mg/kg gem and 1 mg/kg cis on day 6, 50 mg/kg gem on day 9 and 50 mg/kg gem and 1 mg/kg cis on day 12
Group 4: Chemo and RIT combined
Growth curves (previous slides) were fitted to exponential growth curve (R2>0.92) using GraphPad Prism. Doubling time and tumour growth to 50% were provided by the fitted curve.
LL2 tumours were grown in C57 mice (9 days) then treated with gemcitabine and cisplatin (A) or gemcitabine, cisplatin and TSA (B). Tumour volume was measured and the percentage change in tumour volume was calculated. Combination of RIT and chemo±TSA showed synergy in comparison to single agent treatments (
Tumour doubling time (tDt) and time for growth to 50% (TG50) were measured from growth curves of LL2 tumour model treated with 1 cycle therapy (Table 9) or 2 cycle therapy (Table 10).
50 mg/kg Gemcitabine and 2.5 mg/kg Cisplatin on Day 0 and 50 mg/kg Gemcitabine on Day 1.
90Y-DOTA-Apomab was administered at doses of 0.46 Gy, 0.90 Gy, 1.80 Gy, or 3.70 Gy per mouse alone or in combination with chemotherapy.
Volume of Lewis Lung Carcinoma-2 (LL2) tumours was calculated from bi-dimensional measurements made using callipers. Change in tumour volume was calculated as the percentage of tumour volume change compared to that on day 0 (dayt−day0) divided by the volume on day 0 (% [dayt−day0]/day0).
Tumours were excised from control and treated mice after completion of chemotherapy treatment on day 1 (0 h), day 2 (24 h), day 3 (48 h), day 4 (72 h), and day 5 (96 h). Single cell suspensions were prepared from the excised tumours (n=˜4 per time point) and analysed for the content of dead cells using fluorocytometric analysis of 7-AAD staining.
Comparisons were made using two-way analysis of variance and a Bonferroni post-test comparison for cell death measurements, and two-way analysis of variance and a Tukey post-test comparison (Prism GraphPad v.4,0) for tumour doubling time estimations.
The doubling times of tumours from untreated control mice and mice given chemotherapy or RIT singly or in combination are tabulated (see Table 11 and
In contrast, EL4 tumours were cured after La-directed RIT was administered at doses of 1.80 Gy or 3.70 Gy per mouse, and thus indicated that the bystander killing exerted by radiation crossfire was effective in a lymphoma model because lymphoma is highly radiosensitive. Again, in contrast, the dead cell content of EL4 lymphomas approached 70% 7-AAD+ cells after mice were given chemotherapy, and some of the synergistic therapeutic effect achieved by the combining low-dose chemotherapy and low-dose RIT in the treatment of EL4 lymphoma-bearing mice could be attributed to the augmented dead cell content of tumours in mice given chemotherapy.
Therefore, given that chemotherapy produced only a 10% increase in the content of dead cells in LL2 tumours and that RIT alone was ineffective, the addition of RIT to chemotherapy greatly inhibited LL2 tumour growth because the radiosensitising cisplatin and gemcitabine chemotherapy lowered the threshold for induction of cell death by RIT.
Further data are presented in support of this hypothesis using combination treatment with cytotoxic drugs and the histone deacetylase inhibitor (HDACi), trichostatin A (TSA), to show that the combination is very effective in inducing cell death among malignant cells and, therefore, provides the opportunity to maximise target creation.
Adding TSA to cisplatin treatment of Jurkat cells in vitro produces a TSA dose-dependent increase in Apomab-specific binding to dead Jurkat cells (
Similar synergistic interactions were found between gemcitabine and TSA in cells of the pancreatic cancer cell line, PANC-1, in vitro. In these experiments, the TSA doses of 200, 100, 50, 25 and 12.5 ng/mL are equivalent to TSA concentrations of 667, 333, 167, 83 and 42 nM, respectively. Together with the chosen concentrations of gemcitabine, TSA significantly inhibited proliferation of PANG-1 cells in vitro (Piacentini P et al. Virchows Arch 448, 797-804, 2006). Moreover, a moderate dose-dependent effect of TSA was observed on the induction of markers of apoptosis among cultures of PANC-1 cells in vitro (Donadelli M et al. Mol Carcinogenesis 38, 59-69, 2003).
Using the MTS proliferation assay, it was observed that TSA alone inhibited proliferation of PANG-1 cells in vitro. Addition of gemcitabine completely inhibited PANG-1 proliferation at a TSA concentration of 50 nM whereas at a TSA concentration of 200 nM, gemcitabine significantly reduced the numbers of PANG-1 cells in the cultures (
While gemcitabine may not be viewed as a conventional DNA-damaging agent, recent evidence indicates that it produces γH2AX DNA damage foci in a PC-3 tumour xenograft model (McArthur G A et al. J Clin Oncol 24(18S) 3045a, 2006). The synergistic effect of TSA on the induction of cell death among gemcitabine-treated PANG-1 cells together with Apomab-specific binding to the dead cells was evident at the lowest concentration of gemcitabine.
Altogether, it is believed that the data illustrated in
Suspension cultures of Jurkat leukemia cell line and EL4 murine T-lymphoblastic lymphoma cell line were maintained in RPMI-1640 containing 5% FCS (JRH Biosciences Inc., Lenexa, Kans.) and passaged by splitting at 1:10 every 72 h. The anti-La/SS-B 3B9 mAb hybridoma (Tran et al. 2002, Arthritis Rheum. 46(1):202-8) is a murine IgG2a autoantibody, which is crossreactive with human La and which was prepared by Dr M. Bachmann (Oklahoma Medical Research Foundation, OK), was a kind gift from Dr T. P. Gordon (Department of Immunology, Allergy and Arthritis, Flinders Medical Centre, SA, Australia). The isotype control Sal5 (1D4.5) mAb hybridoma, prepared by Dr L. K. Ashman (Medical Science Building, University of Newcastle, NSW, Australia), was kindly supplied by Dr S. McColl (School of Molecular Biosciences, University of Adelaide, SA, Australia). Hybridoma were cultured in RPMI-1640 containing 5% FCS and the produced antibodies were affinity-purified from culture media using protein G columns. FITC-conjugates were prepared according to the manufacturer instructions (Sigma-Aldrich Co., St. Louis, Mo.).
Conjugation of mAb with DOTA-NHS-ESTER
DOTA-NHS-ESTER (Macrocyclics, Dallas, Tex.) was dissolved in DMSO (Sigma-Aldrich Co., St. Louis, Mo.) at 25 mg/mL. Purified 3B9 and Sal5 in 0.1 M sodium phosphate/0.1 M sodium bicarbonate buffer (pH 8.6) were mixed at 2 mg/mL with 50-, 100-, 150- and 200-fold molar excess of DOTA-NHS-ESTER. Control reactions were prepared using equivalent volume of DMSO to replace the NHS-ESTER compound. Reactions were incubated at 23° C. for 2 h with constant rotation and were stopped using 1.5M Tris-HCl (pH 8.3) at 10% v/v final concentration. Removal of unconjugated DOTA and buffer exchange of immunoconjugates was achieved by 5×500 μL PBS washes in 100 kDa cut off microconcentrators as described by manufacturer instructions (Millipore, Billerica, Mass.). Conjugates were stored at 4° C. for further use.
Protein concentration was determined using the BCA protein assay kit as described by manufacturer instructions (Pierce Biotechnology Inc., Rockford, Ill.). Protein concentration was converted from units of mg/mL to μM based on the Mr of IgG (150,000 g/mol). The concentration of DOTA was determined usinu a modified form of the previously described Arsenazo(III) assay (Pippin et al. 1992, Bioconjug Chem 3(4):342-5; Dadachova et al. 1999, Nucl Med Biol, 26(8):977-82; Brady et al. 2004, Nucl Med Biol, 31(6):795-802). Briefly, assays were performed in 96-wells titre plates to reduce the volume used. Stock solutions of Cu:Arsenazo(III) were prepared using 100 μL of 1 mg/mL standard Cu atomic absorption solution (Sigma-Aldrich Co., St. Louis, Mo.), 0.875 mg Arsenazo(III) (Sigma-Aldrich Co., St. Louis, Mo.) and 3 mL of metal free 5M ammonium acetate (Sigma-Aldrich Co., St. Louis, Mo.) in a final 10 mL volume of milliQ water and stored at room temperature (RT) in the dark. Standard concentrations of DOTA were prepared using DOTA-NHS-ESTER dissolved in milliQ water. Aliquots (10 μL) of conjugation reactions and standard DOTA solutions were mixed with 1904 of working dilution (see figure legends) of Cu:Arsenazo(III) solution in milliQ water, incubated at 37° C. for 30 min and absorbance was measured at 630 nm. The concentration of conjugated DOTA was interpolated from the standard curve constructed for the relationship between DOTA standard solutions and the absorbance of Cu:Arsenazo(III) reagent. DOTA/antibody ratio in prepared conjugates was calculated as the ratio of DOTA concentration (μM) to IgG concentration (μM).
SDS Polyacrylamide Gel Electrophoresis (SDS-PAGE) and Western Blotting
SDS-PAGE was performed as per manufacturer instructions using the Hoefer® Mighty Small II SE 250 electrophoresis system (Amersham Biosciences, Piscataway, N.J.) under reducing condition using 12% resolving polyacrylamide gel as per Laemmli (Laemmli U. K., 2005, J. Biol Regul Homeost Agents 19(3-4):105-112). Transfer of polyacrylamide gel onto Hybond-P membrane was carried out as per manufacturer instruction using the TE 22 Mini Tank Transfer Unit (Amersham Biosciences, Piscataway, N.J.). After blocking with 5% skim milk, probing was performed using 5 μg/mL 111In-labelled 3B9 (prepared as described below). Membranes were washed then exposed to x-ray films (3 h at RT) which were developed and documented.
Native polyacrylamide gel electrophoresis (native PAGE) was used to determine the relative fractionation (Rf) value for unmodified and conjugated antibody. Briefly, 7% native gel was prepared using 100 μL APS, 20 μL TEMED (Sigma-Aldrich Co., St. Louis, Mo.), 1.75 mL of 40% acrylamide (Biorad®) and 1.25 mL of 1.5 MTris-HCl (pH 8.6) in a final 10 mL volume of milliQ water. Native PAGE running buffer was prepared by dissolving 3.4 g of glycine and 1.2 g of Tris in 500 mL of milliQ water (pH adjusted to 8.5). Unmodified and conjugated antibody were mixed with equal volume of native PAGE loading dye (20% v/v glycerol, 1.5M Tris-HCl and 0.05% w/v bromophenol blue in milliQ water) and samples were loaded onto gel. Electrophoresis was performed at 200V for 2.5 h and gel was stained using brilliant blue R250 (BBR250) solution (Ig of BBR250 [Sigma-Aldrich Co., St. Louis, Mo.] in 200 mL methanol and 100 mL H2O). The Rf values were determined using the gel analysis program, GelPro Analyzer™ v3.1 (Media Cybernetics Inc., Silver Spring, Md.).
Jurkat cell were fixed and permeabilized by incubation at 1×107 cells/mL in 2% paraformaldehyde for 10 min, diluted 1:10 in −20° C. methanol (5 min) then washed extensively using PBS. Direct immunofluorescent staining was performed using 5 μg/mL of 3B9-FITC or 5 μg/mL Sal5-FITC. Indirect immunofluorescent assays were performed using permeabilized cells incubated with 5 μg/mL of unmodified 3B9, 3B9-DOTA or matching irrelevant isotype (Sal5 or Sal5-DOTA) for 30 min at RT. Cells were washed then incubated in 2 μg/mL of goat anti-mouse IgG Alexa488-conjugated antibody (Invitrogen, Carlsbad, Calif.) for 30 min at RT. Cells were washed and samples were acquired using Becton-Dickinson FACScan™ flow cytometry system (BD Biosciences, San Jose, Calif.). Acquisition was standardized to 10,000 events Flow cytometry data was analyzed using WinMDI v 2.8 (Scripps Research Institute, La Jolla, Calif.).
Activity of 3B9-DOTA conjugates was tested by their ability to inhibit the binding of 3B9-FITC. Briefly, fixed/permeabilized Jurkat cells were incubated for 30 min at RT with 5 μg/mL of 3B9-FITC in the absence or presence of 5, 25, 50 and 100 μg/mL of 3B9-DOTA conjugates. Cells were washed and analyzed by flow cytometry as described above.
Samples (0.1 μg) of unmodified or DOTA-conjugated IgG in native form (PBS) were applied onto nitrocellulose membranes (Amersham Biosciences, Piscataway, N.J.). Membranes were dried and blocked with 5% skim milk for 30 min at RT. Membranes were incubated (30 min at RT) with 1 μg/mL of goat antibodies conjugated with biotin and directed against the mouse IgG or against the Fc or (Fab)2 regions of mouse IgG (Rockland, Gilbertsville, Pa.). Membranes were washed and incubated with 0.1 μg/mL streptavidin-alkaline phosphatase (AP) (Rockland, Gilbertsville, Pa.) for 15 min at RT. Membranes were washed and developed using the BCIP/NBT premixed solution as specified by manufacturer (Sigma-Aldrich Co., St. Louis, Mo.) and analyzed using GelPro Analyzer™.
Kinetics of Labelling of mAb-DOTA with Terbium
Arsenazo(III) reagent was utilized to study the kinetics of labelling of 3B9-DOTA with Terbium (Tb). TbCl3 (Sigma-Aldrich Co., St. Louis, Mo.) was diluted in milliQ water at 20 mg/ml. Stock of Arsenazo(III):metal complexes was prepared by mixing 18.754 of TbCl3 solution with 1.75 mg Arsenazo(III) in 3 mL of 5M ammonium acetate in a final 10 mL of milliQ water. Stock was diluted 1:10 and 90 μL was added to 17.5 μg 3B9-DOTA solutions (10 μL). Absorbance at 630 nm was measured kinetically at 37° C. every 1 min for 1 h.
Radiolabelling of mAb-DOTA with 111In
3B9-DOTA or Sal5-DOTA conjugates were buffer exchanged into 0.2M ammonium acetate (pH 5.5) containing 6 mg/mL ascorbic acid by four washes in 100 kDa cut off microconcentrators. Indium-111 (111InCl3, PerkinElmer Inc., Wellesley, Mass.) and DOTA-conjugates were incubated for 2 h at 37° C. at concentrations of 2 mCi/mL (74 MBq/mL) of 111In and 2 mg/mL of conjugates in (i.e. 1:1 mCi:mg or 37 MBq:mg ratio) 0.2M ammonium acetate buffer containing 6 mg/mL ascorbic acid. In some cases, ascorbic acid which enhances the incorporation of 111In into the conjugates was eliminated from the radiolabelling reaction as interferes with the BCA protein assay kit. Incorporation of 111In was measured as described in next section.
For purification of 111In-labelled conjugates, radiolabelling reactions were washed twice with 400 μL volumes of 0.2M ammonium acetate containing 5 mM EDTA (pH 8.0) then 3 times with 400 μL volumes of PBS in 100 kDa cut off microconcentrators as described earlier. Protein concentration of purified 111In-labelled conjugates was measured using the BCA assay kit and the radioactivity concentration was measured using a specified volume placed in gamma counting tubes and counted using Cobra5010 gamma counter (PerkinElmer Inc., Wellesley, Mass.) which was normalized for 111In counting at 100-350 keV window. Specific radioactivity was measured as cpm from gamma counter per μg of protein present in the counted volume.
Incorporation efficiency was measured using instant thin layer chromatography (ITLC). Briefly, 2 μL aliquots of labelling reactions were mixed with 2 μL of 0.2M ammonium acetate containing 5 mM EDTA (pH 8.0) and applied at 1 cm from the bottom of 1×9 cm ITLC-SG strips (Pall Corporation, East Hills, N.Y.). Chromatography was performed in 0.2M ammonium acetate containing 5 mM EDTA (pH 8.0) as mobile phase and was stopped when solvent front reached 1 cm from the top of the strips. Strips were cut in two halves where the bottom half represented the origin (ori) and the top half represented the solvent front (SF). The activity of the two halves was measured using gamma counter. Incorporation efficiency was calculated as the percentage of activity remaining at the origin to the total activity of the strip [% ori/(ori+SF)].
We have previously described an in vivo model of apoptosis which we have shown specific and preferential accumulation of 3B9 in tumors of chemotherapy treated mice (Al-Ejeh et al., 2007). Briefly, EL4 thymic lymphoma cells (1×106 cells) were injected subcutaneously in the right flanks of 6-8 weeks old C57BL/6 female mice. Mice were housed and treated as per protocols approved by the Animal Ethics Committee at The University of Adelaide and the Animal Ethics Committee at the Institute of Medical and Veterinary Sciences (IMVS). Once the tumor reached 1 cm diameter, mice were treated by intraperitoneal injections of cytotoxic chemotherapy (38 mg/kg etoposide and 50 mg/kg cyclophosphamide) given at time 0 and 24 h. DOTA-conjugates labelled with 111In (100 μg) was injected intravenously at time 0. Mice were euthanized at 48 h, blood was collected by cardiac puncture, and tumors and organs were collected. Blood and organs were weighed and placed in gamma-counter tubes and radioactivity was measured using gamma counter. Radioactivity in organs was normalized to the weight of the organs and accumulation was calculated as the percentage of radioactivity per gram in the organs to the radioactivity of the injected dose at time 0 (% ID/g).
Statistical comparisons were preformed using GraphPad Prism v.4 (GraphPad Software, San Diego, Calif.). Two-way analysis of variances (2-way ANOVA) was used to deduce significant differences in the results. The Bonferroni post-test in the 2-way ANOVA function in GraphPad prism was used to report P values. P values less than 0.05 were considered significant where one, two and three asterisks denote P values less than 0.05, 0.01 and 0.001, respectively.
Previously described assays for the measurement of metal chelators attached to antibodies uses a standard curve for the absorbance (deep blue color) of Cu:Arsenazo(III) solutions of different concentrations. The absorbance of this reagent when mixed with immunoconjugates is then used to interpolate (from standard Cu:Arsenazo(III) curve) the concentration of Cu remaining after chelation which allows calculation of chelated Cu thus representing the concentration of metal chelator (Pippin et al. 1992 supra; Dadachova et al. 1999 supra; Brady et al. 2004 supra). We found that while Cu:Arsenazo(III) standard curve represented dilutions of the deep blue color of the reagent (
Conjugation of 3B9 with DOTA-NHS-ESTER was performed in three separate occasions. The average DOTA/antibody ratios were 2.8±0.3, 8.2±0.3, 11.6±1.1 and 15.0±0.7 for the conjugation conditions of 50-, 100-, 150- and 200-fold molar excess of DOTA-NHS-ESTER to 3B9 (
The avidity of DOTA-conjugated 3B9 was investigated using competition binding assays. As shown in
Detection of 3B9-DOTA conjugates using antibodies against whole IgG molecule or antibodies against the Fc and (Fab)2 regions decreased significantly compared to that of unmodified 3B9. Samples of 3B9 and 3B9-DOTA conjugates fractioned in non-reducing SDS-PAGE showed comparable amounts of protein in these samples as judged by the intensity of BBR250 staining (
Further evidence for the modification of 3B9 during conjugation both in structure and avidity was obtained using indirect immunofluorescent staining of permeabilized Jurkat cells. As shown in
The absorbance of Terbium:Arsenazo(III) reagent mixed with 3B9-DOTA conjugates decreased during 1 h incubation at 37° C. (
There has been reported the specific and saturable accumulation of 3B9 in EL4 tumors after cytotoxic chemotherapy treatment compared to the irrelevant control of matched isotype, Sal5 (Al-Ejeh et al., 2007). This model was used to investigate the significance of the above described modification of antibody properties after conjugation in vivo. Biodistribution of 3B9-DOTA in chemotherapy treated mice was affected when prepared at 200-fold molar excess of DOTA-NHS-ESTER compared to that prepared at 50-fold excess (
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/AU07/01543 | 10/11/2007 | WO | 00 | 1/4/2010 |
| Number | Date | Country | |
|---|---|---|---|
| 60851213 | Oct 2006 | US |
