Glycosyltransferase vectors for treating cancer

TECHNICAL FIELD

[0002] This invention relates generally to the field of virology and cancer therapy. This disclosure provides vectors in which an encoding region for glycosyltransferase is linked to a genetic element that controls transcription in a tumor or tissue specific fashion.

BACKGROUND

[0003] Many forms of cancer are intractable to traditional courses of radiation or small molecule pharmaceuticals. Considerable interest has evolved in developing gene therapy vectors as chemotherapeutic agents.

[0004] A broad variety of therapeutic genes are currently under investigation in preclinical and in clinical studies (Walther et al., Mol. Biotechnol. 13:21, 1999). The candidate genes have very different origins and different mechanisms of action—which include cytokine genes, genes coding for immunostimulatory molecules/antigens, genes encoding bacterial or viral prodrug-activating enzymes (suicide genes), and tumor suppressor genes.

[0005] Some of the putative vectors are based on adenovirus. U.S. Pat. Nos. 5,631,236 and 6,096,718 (Baylor College of Medicine) cover a method of causing regression in a solid tumor, using a vector containing an HSV thymidine kinase (tk) gene, followed by administration of a prodrug such as ganciclovir. U.S. Pat. No. 6,096,718 (Baylor College of Medicine) relates to the use of a replication incompetent adenoviral vector, comprising an HSV tk gene under control of the α-lactalbumin promoter.

[0006] U.S. Pat. No. 5,801,029 and 5,846,945 (Onyx Pharmaceuticals) relate to adenovirus in which the E1a gene has been altered so as not to bind and inactivate tumor suppressor p53 or RB. This prevents the virus from inactivating tumor suppression in normal cells, which means the virus cannot replicate. However, the virus will replicate in cells that have shut off p53 or RB expression through oncogenic transformation.

[0007] U.S. Pat. No. 5,998,205 (GTI/Novartis) pertains to a tissue-specific replication-conditional adenovirus, comprising a transcriptional regulatory sequence (such as the α-fetoprotein promoter) operably linked to adenovirus early replication gene. U.S. Pat. No. 5,698,443 (Calydon) provides replication-conditional adenoviruses controlled by the PSA promoter. Alemany et al. (Cancer Gene Ther. 6:21, 1999) outline complementary adenoviral vectors for oncolysis. One vector contains cis replication elements and E1a under control of a tissue-specific promoter. The supplemental vector contains all other trans-acting adenovirus replication genes. Coinfection leads to controlled killing of hepatocarcinoma cells.

[0008] International Patent Publication WO 98/14593 (Geron) describes an adenovirus construct in which the tk gene is placed under control of the promoter for telomerase reverse transcriptase (TERT). This gene is expressed at high levels in cancer cells of any tissue type, and the vector renders cancer cell lines susceptible to toxic effects of ganciclovir. WO 00/46355 (Geron) describes an oncolytic virus having a genome in which a TERT promoter is linked to a genetic element essential for replication or assembly of the virus, wherein replication of the virus in a cancer cell leads to lysis of the cancer cell.

[0009] Koga et al. (Hu. Gene Ther. 11:1397, 2000) propose a telomerase-specific gene therapy using the hTERT gene promoter linked to the apoptosis gene Caspase-8 (FLICE). Gu et al. (Cancer Res. 60:5359, 2000) reported a binary adenoviral system that induced Bax expression via the hTERT promoter. They found that it elicited tumor-specific apoptosis in vitro and suppressed tumor growth in nude mice.

[0010] Other vectors are based on herpes family viruses, such as herpes simplex type 1 and 2. U.S. Patent 5,728,379 (Georgetown University) relates to replication competent HSV containing a transcriptional regulatory sequence operatively linked to an essential HSV gene. Exemplary is the IPC4 gene under control of the pro-opiomelanocortin promoter.

[0011] Other vectors are based on the retrovirus family. U.S. Patent 5,997,859 and EP 702084 B1 (Chiron) pertain to replication-defective recombinant retrovirus, carrying a vector construct capable of preventing, inhibiting, stabilizing or reversing infections, cancer, or autoimmune disease. The virus directs expression of an enzyme not normally expressed in the cells that converts a compound into a cytotoxic form. Exemplary is the HSV tk gene. WO 99/08692 proposes the use of reovirus in treating cancer, particularly ras-mediated neoplasms.

[0012] These proposed therapeutic agents are not currently approved for commercial use in the United States. There is a need to develop new constructs to improve efficacy and specificity of cancer treatment.

SUMMARY OF THE INVENTION

[0013] This invention provides a system for killing cancer cells in vitro or in vivo, using a polynucleotide encoding a glycosyltransferase under control of a tumor specific or tissue specific transcriptional control element. The glycosyltransferase typically forms a determinant on the cell surface to which some or all humans have naturally occurring antibody. In this manner, cancer cells will be culled on an ongoing basis by antibody already present in the circulation, without the need to follow the vector with an effector agent.

[0014] One embodiment of the invention is a polynucleotide as already described. Suitable glycosyltransferase enzymes include but are not limited to histo blood group A or B transferase from any upper primate (particularly human), and α(1,3)galactosyltransferase (α1,3GT) of any mammal that forms the Galα(1,3)Gal xenoantigen.

[0015] The transcriptional control element can be a tissue specific promoter, as exemplified below. Alternatively, the control element can be a tumor specific promoter, as exemplified below. Of particular interest is the promoter for telomerase reverse transcriptase (SEQ. ID NO:1). The polynucleotide can take the form of a viral vector (for example, adenovirus, herpes virus, or retrovirus), naked DNA, or a lipid composition (for example, a neutral or anionic lipid envelope, or a cationic liposome or micelle) that has a DNA or RNA component.

[0016] Polynucleotides of the invention can be used to prepare a medicament for human treatment, especially for conditions associated with hyperproliferation, such as cancer and other neoplasias.

[0017] Another embodiment of the invention is a polypeptide with glycosyltransferase activity, which comprises a consensus of mammalian α1,3GT sequences, or a humanized α1,3GT sequence, or catalytic subfragment thereof.

[0018] Also provided is a method of killing a cancer cell, comprising combining the cancer cell with a polynucleotide as already described. The invention includes a system for testing and manufacturing the glycosyltransferase vectors of this invention. The invention can be used for treating cancer in a subject by administering to the subject a polynucleotide as already described.

[0019] Other embodiments of the invention will be apparent from the description that follows.

DRAWINGS

[0020]
FIG. 1 is a map of adenovirus vector designated pGRN376, in which the promoter for telomerase reverse transcriptase (TERT) controls expression of the tk gene (Example 1).

[0021]
FIG. 2 is a photographic reproduction showing the effects of replication-conditional adenovirus on normal and cancer-derived cell lines (Example 2).

[0022]
FIG. 3 is a sequence listing comparing the human blood group A and B transferase amino acid sequences with α(1,3) galactosyltransferase (α1,3GT) of other species. A consensus version and a humanized version of α1,3GT are shown as SEQ. ID NOs:12 & 13. (−) represents a sequence gap; (. ) indicates a residue identical with the aligned marmoset α1,3GT sequence (Example 3). Other sequences shown in this figure are listed in Table 2.

[0023]
FIG. 4 is a sequence listing comparing the marmoset α1,3GT encoding sequence with the human α1,3GT pseudogene. The humanized α1,3GT encoding sequence is shown as SEQ. ID NO:16 (Example 3). The sequences shown in this figure are listed in Table 2.

DETAILED DESCRIPTION

[0024] A long-sought objective in cancer treatment is to design a therapeutic agent that effectively kills cancer cells wherever they are located, while sparing other cells in the vicinity that do not bear the malignant phenotype.

[0025] The invention described in this disclosure solves the problem by providing a therapeutic vector that encodes an enzyme that forms a target molecule on the cell surface that can be targeted by antibody in situ. Particularly effective are so-called natural antibodies that recognize features of foreign complex carbohydrates. A number of naturally occurring anti-carbohydrate antibodies are present in the circulation of humans without deliberate immunization. It is thought that these antibodies arise from cross-reacting mucins and other carbohydrate-bearing substances that people are routinely exposed to through their diet.

[0026] In one aspect of this invention, the carbohydrate targets are produced in greater abundance on tumor cells, because expression of the enzyme that makes the target is controlled by a transcriptional control element that is tumor or tissue specific. Tumor-specific targeting relies on control elements taken from genes expressed predominantly in cells that undergo repeated proliferation, or that are relatively undifferentiated. Such vectors are effective for treating a wide variety of tumor types at the primary site or elsewhere. Tissue-specific targeting relies on control elements taken from genes expressed in particular tissue types. Such vectors are especially useful for treating metastases, or tumors in which the tissue-specific element is relatively more abundant.

[0027] Treatment is effected by administering the vector systemically or locally so that it can migrate to and transfect the tumor cells causing the disease. The vector then causes expression of the new carbohydrate structure at the cell surface. This becomes a target for antibody in the circulation (or other components of the immune system, such as cytotoxic T cells, ADCC cells, or T helper/inducer cells) —which in turn leads to a number of possible effects—complement-mediated lysis, opsonization, cytotoxic killing, cytokine and interferon secretion, and inflammatory response.

[0028] This system is believed to offer two advantages over previous approaches to gene therapy for cancer.

[0029] The first advantage is that it can provide ongoing surveillance against the emergence of new malignancies. This is available when using a tumor-specific expression vector, such as the TERT promoter described below, and when the vector is capable of replication or remains expressible by the cell. In cancer cells, the vector will cause expression of the target carbohydrate, causing them to be recognized and eliminated by antibody. In cells that are not actively malignant, the vector will remain quiescent—until such time as the cell reverts to the cancer phenotype—whereupon the target carbohydrate will be expressed de novo, and the cell becomes eliminated in its turn. Since naturally occurring antibody is persistently available, there is no need to readminister an effector drug to eradicate any newly activated cancer cells.

[0030] The second advantage is that glycosyltransferases potentially provide a second level of specificity for malignant cells. In using tumor-specific promoters to drive gene expression, there is at least a theoretical concern that the vector may also have an effect on non-cancerous cells that up-regulate the promoter transiently as part of the normal replicative process of the cell. For example, TERT is expressed transiently by some actively growing stem cells, lymphocytes, and germinal tissue.

[0031] The potential second layer of specificity provided by glycosyltransferase is related to the density of carbohydrate determinants on the surface of certain types of progenitor cells. Immune lysis of cells through glycolipid antigen depends primarily on IgG antibody. The IgG molecule must span two antigenic determinants with its two combining sites in order to activate complement—binding to only one determinant (termed monogamous bivalency) is insufficient. This means there is a minimum density of determinants that must be present in order for the antibody to activate complement.

[0032] Fetal red cells bear a low density of ABO blood group determinants, attributable to paucity of branches in the oligosaccharide. This means that ABO blood group IgG antibodies can only bind monogamously (Romans et al., J. Immunol. 124:2807, 1980). If other fetal and embryonic cells express the branching enzyme in the same limited fashion, then they may also be less susceptible to complement lysis mediated by antibodies directed against any part of the same complex carbohydrate.

[0033] This theoretical rationale is provided to enhance the reader's appreciation of the invention. Those skilled in the art will appreciate that there are other advantages in the invention beyond those indicated above. This explanation is not meant to limit the claimed invention in any way.

[0034] Further explanation of the making and use of the vector constructs of the invention is provided in the sections that follow.

[0035] Definitions

[0036] The term “polynucleotide” refers to a polymeric form of nucleotides of any length. Included are genes and gene fragments, mRNA, tRNA, rRNA, ribozymes, cDNA, recombinant polynucleotides, branched polynucleotides, plasmids, vectors, isolated DNA and RNA, nucleic acid probes, and primers. As used in this disclosure, the term polynucleotides refer interchangeably to double- and single-stranded molecules. Unless otherwise specified or required, any embodiment of the invention that is a polynucleotide encompasses both a double-stranded form, and each of the two complementary single-stranded forms known or predicted to make up the double-stranded form.

[0037] A cell is said to be “genetically altered”, “transfected”, or “genetically transformed” when a polynucleotide has been transferred into the cell by any suitable means of artificial manipulation, or where the cell is a progeny of the originally altered cell that has inherited the polynucleotide. The polynucleotide will often comprise a transcribable sequence encoding a protein of interest, which enables the cell to express the protein at an elevated level. The genetic alteration is said to be “inheritable” if progeny of the altered cell have the same alteration.

[0038] A “control element” or “control sequence” is a nucleotide sequence that contributes to the functional regulation of a polynucleotide, such as replication, duplication, transcription, splicing, translation, or degradation of the polynucleotide. Transcriptional control elements include promoters, enhancers, and repressors.

[0039] Particular gene sequences referred to as promoters, like the “TERT promoter”, or the “PSA promoter”, are polynucleotide sequences derived from the gene referred to that promote transcription of an operatively linked gene expression product. It is recognized that various portions of the upstream and intron untranslated gene sequence may in some instances contribute to promoter activity, and that all or any subset of these portions may be present in the genetically engineered construct referred to. The promoter may be based on the gene sequence of any species having the gene, unless explicitly restricted, and may incorporate any additions, substitutions or deletions desirable, as long as the ability to promote transcription in the target tissue. Genetic constructs designed for treatment of humans may comprise a segment that at least 90% identical to a promoter sequence of a human gene. A particular sequence can be tested for activity and specificity, for example, by operatively linking to a reporter gene (Example 1).

[0040] Genetic elements are said to be “operatively linked” if they are in a structural relationship permitting them to operate in a manner according to their expected function. For instance, if a promoter helps initiate transcription of the coding sequence, the coding sequence can be referred to as operatively linked to (or under control of) the promoter. There may be intervening sequence between the promoter and coding region so long as this functional relationship is maintained.

[0041] In the context of encoding sequences, promoters, and other gene elements, the term “heterologous” indicates that the element is derived from a genotypically distinct entity from that of the rest of the entity to which it is being compared. For example, a promoter or gene introduced by genetic engineering techniques into a context; in which it does not occur in nature is said to be a heterologous polynucleotide. An “endogenous” genetic element is an element that is in the same place in the chromosome where it occurs in nature, although other gene elements may be artificially introduced into a neighboring position.

[0042] The terms “polypeptide”, “peptide” and “protein” are used interchangeably to refer to polymers of amino acids of any length. The polymer may comprise modified amino acids, it may be linear or branched, and it may be interrupted by non-amino acids.

[0043] The term “antibody” as used in this disclosure refers to both polyclonal and monoclonal antibody. The ambit of the term deliberately encompasses not only intact immunoglobulin molecules, but also such fragments and genetically engineered derivatives of immunoglobulin molecules, T cell receptors, and their equivalents as may be prepared by techniques known in the art, and which retain binding specificity of the antigen combining site.

[0044] General Techniques

[0045] Methods in molecular genetics and genetic engineering are described generally in the current editions of Molecular Cloning: A Laboratory Manual, (Sambrook et al.); Oligonucleotide Synthesis (M. J. Gait, ed.,); Animal Cell Culture (R. I. Freshney, ed.); Gene Transfer Vectors for Mammalian Cells (Miller & Calos, eds.); Current Protocols in Molecular Biology and Short Protocols in Molecular Biology, 3rd Edition (F. M. Ausubel et al., eds.); and Recombinant DNA Methodology (R. Wu ed., Academic Press). Reagents, cloning vectors, and kits for genetic manipulation referred to in this disclosure are available from commercial vendors such as BioRad, Stratagene, Invitrogen, and ClonTech.

[0046] For a description of the molecular biology of cancer, the reader is referred to Principles of Molecular Oncology (M. H. Bronchud et al. eds., Humana Press, 2000); The Biological Basis of Cancer (R. G. McKinnel et al. eds., Cambridge University Press, 1998); and Molecular Genetics of Cancer (J. K. Cowell ed., Bios Scientific Publishers, 1999).

[0047] General techniques for the development, testing, and administration of biomolecular chemotherapeutics are provided in Gene Therapy of Cancer, Adv. Exp. Med. Biol. vol. 451 (P. Walden ed., Plenum Publishing Corp., 1998); Cancer Gene Therapy, Adv. Exp. Med. Biol. vol. 465(N. A. Habib ed., Kluwer Academic Pub, 2000); and Gene Therapy of Cancer: Methods and Protocols, Meth. Mol. Med. vol. 35 (W. Walther & U. Stein eds., Humana Press, 2000).

[0048] Effector Genes for Tumor Cell Depletion

[0049] The vectors of this invention comprise an encoding region that forms a carbohydrate determinant on the cell surface as a target for cancer cell lysis.

[0050] Exemplary are glycosyltransferases that synthesize an alloantigen or xenoantigen widely expressed on different tissue types.

[0051] In humans, an α(1,2)fucosyltransferase uses N-acetyl lactosamine acceptor groups on cell surface glycoproteins and glycolipids to form Fucα(1,2)Galβ(1,4)GlocNAc, which is blood group H substance. This in turn serves as an acceptor for the ABO histo blood group transferases, which form terminal allodeterminants on the complex carbohydrate. Blood group A transferase adds GaINAc to form GalNAcα(1,3)Gal (A substance). Blood group B transferase adds Gal instead to form Galα(1,3)Gal (B substance).

[0052] According to the blood group of an individual, one or both of these transferases are expressed in essentially all nucleated cells, resulting in expression of A and B substance on the cell surface. Red cells also abundantly present A and B substance, by virtue of synthesis before enucleation, and subsequent adsorption of glycolipids from plasma. Naturally occurring antibodies circulate in the blood that react against the ABO determinants that are not self-antigens. One advantage of using an ABO transferase as the effector sequence is that the H precursor substance will be available on the surface membrane of virtually any tumor.

[0053] The nucleotide and protein sequence of A transferase and B transferase are provided below. See also U.S. Pat. Nos. 5,068,191 and 5,326,857. The two enzymes are close homologs of each other, differing by only a few amino acids. Another advantage of using an ABO transferase as the effector sequence is that the expressed protein is of human origin, and unlikely to be immunogenic by virtue of its similarity to another gene product expressed as a self antigen in the patient being treated.

[0054] Mammals other than humans, apes and Old World monkeys do not form H precursor substance, but instead convert the N-acetyl lactosamine acceptor into the Galα(1,3)Gal determinant. Galα(1,3)Gal epitope is expressed prominently on the surface of nucleated cells, including hepatic cells, renal cells, and vascular endothelium—and is the main target for the natural antibodies mediating xenograft rejection (reviewed by Joziasse et al., Biochim. Biophys. Acta 1455:403, 1999; Sandrin et al., Frontiers Biosci. 2:31,1997).

[0055] The Galα(1,3)Gal epitope is made by a specific enzyme, α(1,3)galactosyltransferase (α1,3GT). In humans and other primates that don't express the Galα(1,3)Gal product, the α1,3GT locus is inactivated (Gailili et al., Proc. Natl. Acad. Sci. USA 15:7401, 1991). There are frameshift and nonsense mutations within the locus, turning it into a non-functional, processed pseudogene (Laarsen et al., J. Biol. Chem. 265:7055,1990; Joziasse et al., J. Biol. Chem. 266:6991,1991).

[0056] For use in this invention, α1,3GT of any species can be used. A number of α1,3GT sequences are provided below. For use in human therapy, it may be beneficial to use an α1,3GT that differs as little as possible from the human pseudogene sequence, while retaining the same specificity. The complete marmoset α1,3GT sequence is provided below, and can be humanized by substituting residues from the human pseudogene that do not alter the binding or catalytic site. If desired, glycosyltransferases can also be truncated down to the minimal size of the catalytically active enzyme (Henion et al., Glycobiology 4:193, 1994).

[0057] Other glycosyltransferases can also be identified for use in this invention. Candidates include transferases responsible for other carbohydrate blood group alloantigens (for example, Lewis, P, li blood groups). Candidates also include non-mammalian glycosyltransferases, and transferases responsible for making determinants present on embryonic cells of humans and other species that are not found on most adult cells.

[0058] The choice of a particular transferase may involve a number of considerations and routine empirical testing. One consideration is the density of determinants formed on transfected cells. As discussed earlier, certain glycosyltransferases may synthesize a lower density of determinants on stem cells by virtue of the relative paucity of branched precursor substances on those cells. By judicious selection of the transferase, it may be possible to titrated the density of determinants formed. For example, A- and B-transferases will have exclusive access to H substance if transfected into type O cells, or will compete 1:1 with each other as counterparts. α1,3GT is expected to produce less determinant, because it must compete in humans with the α(1,2)fucosyltransferase that forms H substance. It has been found that α1,3GT fairs less well in this competition because of its position in the Golgi, which in turn is a function of the N-terminal membrane-anchoring domain. It is possible to switch the α(1,2)fucosyltransferase cytoplasmic domain onto α1,3GT in order to increase the density of Galα(1,3)Gal epitopes produced (Osman et al., J. Biol. Chem. 271:33105,1996).

[0059] Transcriptional Control Elements for Tumor Targeting

[0060] The control element is selected with a view to the protein expression patterns in cancer cells compared with non-malignant cells that will also be exposed to the vector.

[0061] Many tumor-specific transcriptional control elements can be used in this invention. These control elements cause elevated transcription of the encoding sequence they are linked to in tumor cells of a variety of different types. Examples are promoters that control telomerase reverse transcriptase (TERT), carcinoembryonic antigen (CEA), hypoxia-responsive element (HRE), autocrine motility factor receptor (Grp78), L-plastin, and hexokinase II.

[0062] The promoter for TERT is exemplary. Sequence of the human TERT gene (including upstream promoter sequence) is provided below. The reader is also referred to U.K. Patent GB 2321642 B (Cech et al., Geron Corporation and U. Colorado), International Patent Publications WO 00/46355 (Morin et al., Geron Corporation), WO 99/33998 (Hagen et al., Bayer Aktiengesellschaft), and Horikawa et al. (Cancer Res., 59:826, 1999). Other TERT sequences can also be used; the mouse sequence is provided in WO 99/27113 (Morin et al., Geron Corporation). A lambda phage clone designated λGΦ5, containing ˜13,500 bases upstream from the hTERT encoding sequence, is available from the ATCC under Accession No. 98505. Example 1 illustrates the testing and use of TERT promoter sequences in vector expression systems. Those skilled in the art will appreciate that promoter sequences not contained in λGΦ5 but homologous and capable of promoting preferential expression in cancer cells can be used with similar effect. For example, a TERT promoter can comprise a sequence of 25, 50, 100, or 200 consecutive nucleotides that is 80%, 90%, or 100% identical (or can hybridize under stringent conditions) to a sequence contained in SEQ. ID NO:1.

[0063] As an alternative, a transcriptional control element can be used that is tissue-specific. Constructs of this kind will cause preferential expression of the glycosyltransferase, if the level of expression of the endogenous gene is higher in tumor cells than in non-malignant tissue of the same type. They are also useful to treat tumors that have metastasized away from the primary site. Examples are promoters that control transcription of albumin (liver-specific), a-fetoprotein (AFP, liver-specific), prostate-specific antigen (PSA, prostate-specific), mitochondrial creatine kinase (MCK, muscle-specific), myelin basic protein (MBP, oligodendrocyte-specific), glial fibrillary acidic protein (GFAP, glial cell specific), and neuron-specific enolase (NSE, neuron-specific). See U.S. Pat. No. 5,871,726 (Calydon), WO 98/39466 (Calydon), U.S. Pat. No. 5998205 (Genetic Therapy Inc.).

[0064] Additional promoters suitable for use in this invention can be taken from other genes that are preferentially expressed in tumor cells. Such genes can be identified, for example, by differential display and comparative genomic hybridization: see U.S. Pat. Nos. 5,759,776 and 5,776,683. Alternatively, microarray analysis can be performed cDNA fragments of candidate genes in a 96 or 384 well format, and then spotted directly onto glass slides. To compare mRNA preparations from cancer cells and a matched non-malignant control, one preparation is converted into Cy3-labeled cDNA, while the other is converted into Cy5-labeled cDNA. The two cDNA preparations are hybridized simultaneously to the microarray slide, and then washed to eliminate non-specific binding. Any given spot on the array will bind each of the cDNA products in proportion to abundance of the transcript in the two original mRNA preparations. The slide is then scanned at wavelengths appropriate for each of the labels, and the relative abundance of mRNA is determined. Preferably, the level of expression of the effector gene will be at least 5-fold or even 25-fold higher in the undifferentiated cells relative to the differentiated cells. Having identified transcriptional control elements of interest, specificity can be tested in a reporter construct where the control element is used to control transcription of a reporter gene, such as green fluorescence protein, secreted alkaline phosphatase, or β-galactosidase.

[0065] Formulation and Administration of Cancer Therapeutics

[0066] A number of viral vectors are suitable for cancer gene therapy according to the invention. For general principles in vector construction, the reader is referred to Viral Vectors for Gene Therapy (B. J. Carter, Biotechnology 1999, XVIII, 562 p. 393,1999).

[0067] Adenovirus vectors provide transient gene expression, and can be constructed to be replication competent or replication incompetent. For general principles in adenovirus construction, see Danthinne et al., Gene Ther. 7:1707, 2000, Bilbao et al., Adv. Exp. med. Biol. 451:365, 1998, and U.S. Pat. No. 5,631,236 (Baylor College of Medicine), U.S. Pat. No. 5,670,488 (Genzyme), U.S. Pat. No. 5,698,443 (Calydon), U.S. Pat. No. 5,712,136 (GenVec), U.S. Pat. No. 5,880,102 (Duke University), U.S. Pat. No. 5,994,128 (IntroGene), U.S. Pat. No. 6,040,174 (Transgene), U.S. Pat. No. 6,096,718 (Gene Targeting Corp).

[0068] Retrovirus vectors can be constructed to provide gene expression that is inheritable by progeny of the cell it infects. U.S. Pat. Nos. 5,698,446 and 6,133,029 (Chiron). Vectors can also be based on viruses of the herpes family. U.S. Pat. No. 5,728,379 (Georgetown University). Adeno-associated virus, reovirus, and a number of other viruses are also suitable.

[0069] As an alternative, the vectors of this invention can be constructed on a technology which is not virus based. Suitable are nucleic acid-lipid complexes of various kinds, where the lipid protects the nucleic acid en route to the tumor, and facilitates entry into the cell. One form is cationic liposomes or micelles. Li et al. (Gene Ther. 5:930,1998) generally describe cationic lipid—promoter—DNA complexes for intravenous gene delivery. Another form is neutral or anionic liposomes, where the DNA is encapsulated in a lipid envelope that may express other components to inhibit non-specific uptake. U.S. Pat. No. 5,981,501 (Inex) and U.S. Pat. No. 6,043,094 (Sequus/Alza). The composition may resemble an artificial viral envelope. U.S. Pat. No. 5,766,625 (U. Florida) and WO 97/04748 (Advanced Therapies).

[0070] Also part of the invention are viral constructs in which gene expression is cell-specific, and the virus itself is replication conditional. See generally Todo et al., Cancer Gene Ther. 7:939, 2000; and WO 00/46355 (Geron). In this embodiment, the glycosyltransferase encoding region is under control of a tissue or tumor specific control element—and a gene essential for replication or packaging of the virus is also under control of a tissue or tumor-specific control element. Genes required for replication of adenovirus include E1a, E1b, E2, and E4. Genes required for replication of HSV include ICP6 and ICP4. Glycosyltransferase expression and viral replication can be controlled by the same promoter—or they can be controlled by different promoters, providing a further level of specificity for cancer cells.

[0071] Constructs comprising different glycosyltransferase encoding regions and different regulatory control elements can be tested and compared in several different assay systems. Suitable cells for these assays include human tumor cells expressing the gene from which the regulatory control element of the virus is taken (e.g., hTERT), matched with cell lines from a similar non-malignant tissue, or a tissue expressing about the same density of acceptor substrate for the glycosyltransferase. The cells can be transduced with the test vector, with a vector not comprising the glycosyltransferase sequence (negative control), and with a vector in which the glycosyltransferase is under control of a constitutive promoter (such as CMV or PGK).

[0072] Expression of the glycosyltransferase can be detected at the RNA level by RT-PCR, and at the protein level by immunocytochemistry, according to standard techniques. Expression of the cell-surface determinant synthesized by the glycosyltransferase can be detected using epitope-specific antibody or lectin, for example, by FACS. Human type B serum contains antibodies to A substance and to the Galα(1,3)Gal xenoantigen. The “IB4” lectin from Bandeiraea (Griffonia) simplicifolia (Sigma Cat. L 3019) is specific for α-D-galactosyl residues and binds both the Galα(1,3)Gal epitope, and B blood group substance. Antigen density can be compared for vectors with different promoters and effectors in quantitative assays using labeled monovalent antibody. Monogamous bivalency (the ability or inability of specific IgG to bind by more than one combining site) can be measured in suspended cells using the antiglobulin test (Romans et al., J. Immunol. 124:2807, 1980).

[0073] Ultimately, efficacy of the constructs of this invention can be assessed by their ability to trigger complement-mediated tumor cell lysis. A panel of tumor and non-tumor lines in culture is transfected with the vector, and then exposed to a source of epitope-specific antibody plus complement. For typical vectors encoding α1,3GT, fresh human serum will contain sufficient antibody and complement to cause specific lysis. For typical vectors encoding an A or B transferase, fresh serum of O blood type should cause lysis. If fresh serum is not available for the product of a particular glycosyltransferase, lysis can be measured using specific antibody and guinea pig complement. Rather than measuring lysis, the cells can be treated for a brief interval and then injected into a suitable mouse model, to determine if the treatment inhibits tumor growth.

[0074] General validation of the approach and titration of virus can be confirmed using a α1,3GT vector in α1,3GT knockout mice. U.S. Pat. No. 5,849,991 (Bresatch) reports mice that are homozygous for inactivated α1,3GT, resulting in lack of expression of Galα(1,3)Gal epitope, as determined by specific antibody. A model is developed in which the mice are injected with a representative human cancer cell line, such as a glioma. After solid tumors have developed of a sizeable diameter, the mice are injected intravenously or intratumorally with the α1,3GT vector. A dose of 105 to 108 pfu is the predicted test range for HSV vectors. Once the α1,3GT is expressed, anti-Galα(1,3)Gal in the plasma of these mice should opsonize the tumor cells, slowing tumor growth, potentially causing regression and increased survival.

[0075] Treatment of human patients having a tumor depends on the nature of the vectors available and the carbohydrate determinants naturally expressed on their cells. Patients of blood type O (˜46% of the U.S. population) will have natural antibody to both A and B substance, and can be treated with a vector encoding either A or B transferase. Patients of blood type A (˜38%) or B (˜12%) will have natural antibody to the opposite determinant, and can be treated with a vector encoding the corresponding transferases. Patients of blood type AB (˜4% of the population) will not be treatable using either vector. It is possible to use a mixture of A and B transferase vectors as a universal reagent for patients of blood types A, B, and O (˜96% of the population). The lytic potential of the mixture may be somewhat reduced in blood types A and B, since the transferases will be codominantly expressed.

[0076] A universal reagent suitable for treating all ABO blood groups is a vector made using the α1,3GT transferase. Since humans don't have the anti-Galα(1,3)Gal epitope, essentially everyone should have naturally occurring antibody. α1,3GT must compete in humans for the N-acetyl lactosamine acceptor substrate with the α(1,2)fucosyltransferase that makes H substance. Since α1,3GT fairs less well in this competition because of its position in the Golgi (Osman et al., J. Biol. Chem. 271:33105, 1996), a higher density of epitope will be formed by a construct that encodes the N-terminal membrane anchoring domain of the α(1,2)fucosyltransferase fused to the extramembrane catalytic domain of α1,3GT.

[0077] Dosage and formulation of medicaments intended for human therapy are designed based on the animal model experiments. For general guidance on formulation and testing of medicament formulations for human administration, the reader is referred to Biopharmaceutical Drug Design and Development (S. Wu-Pong et al. eds, Humana Press 1999); Biopharmaceuticals: Biochemistry and Biotechnology (G. Walsh, John Wiley & Sons, 1998); and the most current edition of Remington: The Science and Practice of Pharmacy (A. Gennaro, Lippincott, Williams & Wilkins). Pharmaceutical compositions of this invention may be packaged in a container with written instructions for use of the cells in human therapy, and the treatment of cancer.

[0078] The examples that follow are provided by way of further illustration, and are not meant to limit the claimed invention.

EXAMPLES

Example 1

Preparation of Vectors Controlling Transcription in Cells Expressing Telomerase Reverse Transcriptase

[0079] The lambda clone designated λGΦ5 containing the hTERT promoter is deposited with the American Type Culture Collection (ATCC), 10801 University Blvd., Manassas, Va. 20110 U.S.A., under Accession No. 98505. λGΦ5 contains a 15.3 kbp insert including approximately 13,500 bases upstream from the hTERT coding sequence.

[0080] A Not1 fragment containing the hTERT promoter sequences was subcloned into the Not1 site of pUC derived plasmid, which was designated pGRN142. A subclone (plasmid pGRN140) containing a 9 kb Ncol fragment (with hTERT gene sequence and about 4 to 5 kb of lambda vector sequence) was partially sequenced to determine the orientation of the insert. pGRN140 was digested using Sall to remove lambda vector sequences, the resulting plasmid (with removed lambda sequences) designated pGRN144. The pGRN144 insert was then sequenced.

[0081] SEQ. ID NO:1 is a listing of the sequence data obtained. Nucleotides 1-43 and 15376-15418 are plasmid sequence. Thus, the genomic insert begins at residue 44 and ends at residue 15375. The beginning of the cloned cDNA fragment corresponds to residue 13490. There are Alu sequence elements located ˜1700 base pairs upstream. The sequence of the hTERT insert of pGRN142 can now be obtained from GenBank (http://www.ncbi.nlm.nih.gov/) under Accession PGRN142.INS AF121948. Numbering of hTERT residues for plasmids in the following description begins from the translation initiation codon, according to standard practice in the field. The hTERT ATG codon (the translation initiation site) begins at residue 13545 of SEQ. ID NO:1. Thus, position −1, the first upstream residue, corresponds to nucleotide 13544 in SEQ. ID NO:1.

[0082] Expression studies were conducted with reporter constructs comprising various hTERT upstream and intron sequences. A BgIII-Eco47IIII fragment from pGRN144 (described above) was digested and cloned into the BgIII-NruI site of pSEAP2Basic (ClonTech, San Diego, Calif.) to produce plasmid designated pGRN148. A second reporter-promoter, plasmid pGRN150 was made by inserting the BgIII-Fspl fragment from pGRN144 into the BgIII-NruI sites of pSEAP2. Plasmid pGRN173 was constructed by using the EcoRV-Stul (from +445 to −2482) fragment from pGRN144. This makes a promoter reporter plasmid that contains the promoter region of hTERT from approximately 2.5 kb upstream from the start of the hTERT open reading frame to just after the first intron within the coding region, with the initiating Met codon of the hTERT open reading frame changed to Leu. Plasmid pGRN175 was made by APA1(Klenow blunt)-SRF1 digestion and religation of pGRN150 to delete most of the Genomic sequence upstream of hTERT. This makes a promoter/reporter plasmid that uses 204 nucleotides of hTERT upstream sequences (from position −36 to −117). Plasmid pGRN176 was made by PML1-SRF1 religation of pGRN150 to delete most of the hTERT upstream sequences. This makes a promoter/reporter plasmid that uses 204 nucleotides of hTERT upstream sequences (from position −36 to −239).

[0083] Levels of secreted placental alkaline phosphatase (SEAP) activity were detected using the chemiluminescent substrate CSPDTM (ClonTech). SEAP activity detected in the culture medium was found to be directly proportional to changes in intracellular concentrations of SEAP mRNA. The pGRN148 and pGRN150 plasmids (hTERT promoter-reporter) and the pSEAP2 plasmid (positive control, containing the SV40 early promoter and enhancer) were transfected into test cell lines. pGRN148 and pGRN150 constructs drove SEAP expression as efficiently as the pSEAP2 in immortal (tumor-derived) cell lines. Only the pSEAP2 control gave detectable activity in mortal cells.

[0084] The ability of the hTERT promoter to specifically drive the expression of the thymidine kinase (tk) gene in tumor cells was tested using a variety of constructs: One construct, designated pGRN266, contains an EcoRI-FseI PCR fragment with the tk gene cloned into the EcoRI-FseI sites of pGRN263. pGRN263, containing approximately 2.5 kb of hTERT promoter sequence, is similar to pGRN150, but contains a neomycin gene as selection marker. pGRN267 contains an EcoRI-FseI PCR fragment with the tk gene cloned into the EcoRI-FseI sites of pGRN264. pGRN264, containing approximately 210 bp of hTERT promoter sequence, is similar to pGRN176, but contains a neomycin gene as selection marker. pGRN268 contains an EcoRI-Xbal PCR fragment with the tk gene cloned into the EcoRI-Xbal (unmethylated) sites of pGRN265. pGRN265, containing approximately 90 bp of hTERT promoter sequence, is similar to pGRN175, but contains a neomycin gene as selection marker.

[0085] These hTERT promoter/tk constructs, pGRN266, pGRN267 and pGRN268, were re-introduced into mammalian cells and tk/+ stable clones (and/or mass populations) were selected. Ganciclovir treatment in vitro of the tk/+ cells resulted in selective destruction of all tumor lines tested, including 143B, 293, HT1080, Bxpc-3′, DAOY and NIH3T3. Ganciclovir treatment had no effect on normal BJ cells.

[0086]
FIG. 1 is a map of the TPAC adenovector pGRN376. It was made by cloning the NOT1-BAMH1 fragment from pGRN267 into the NOT1-BGL2 sites of pAdBN (Quantum Biotech). The 7185 bp vector comprises the herpes simplex thymidine kinase (tk) gene under control of the medium-length hTERT promoter sequence.

Example 2

Killing Cancer Cells Using Vectors Controlled by the TERT Promoter

[0087] A replication-conditional adenovirus was constructed by placing a gene involved in viral replication under control of the hTERT promoter, which should activate transcription in telomerase-expressing cancer cells. The viral construct comprised the Inverted Terminal Repeat (ITR) from adenovirus Ad2; followed by the hTERT medium-length promoter (phTERT176) operably linked to the adenovirus E1a region; followed by the rest of the adenovirus deleted for the E3 region (ΔE3). As a positive control, a similar construct was made in which E1a was placed under control of the CMV promoter, which should activate transcription in any cell.

[0088] Reagents were obtained as follows. pBR322, restriction enzymes: NEB, Beverly, Mass. Adenovirus Type 2 (Ad2), tissue culture reagents: Gibco/BRL, Grand Island, N.Y. Profection Mammalian Transfection Systems: Promega, Madison, Wis. Tumor and Normal Cell lines: ATCC, Manassas, Va., except BJ line, which was obtained from J. Smith, U. of Texas Southwestern Medical Center.

[0089] Briefly, a pBR322-based plasmid was constructed which contains the Adenovirus Type 2 genome with deletions from 356-548nt (E1a promoter region) and 27971-30937nt (E3). A multiple cloning region was inserted at the point of deletion of the E1a promoter, and hTERT promoter (−239 to −36nt) or CMV promoter (−524 to −9nt) was subsequently cloned. Numbering of the CMV sequence is in accordance with Akrigg et al., Virus Res. 2:107, 1985. Numbering of the Ad2 sequence is in accordance with “DNA Tumor Viruses: Molecular Biology of Tumor Viruses”, J. Tooze ed., Cold Spring Harbor Laboratory, N.Y. These plasmid DNAs were digested with SnaBI to liberate ITRs, then phenol-chloroform extracted, precipitated and transfected into 293A cells for propagation of the virus. Several rounds of plaque purifications were performed using A549 cells, and a final isolate was expanded on these same cells. Viruses were titered by plaque assay on 293A cells, and tested for the presence of 5′ WT Ad sequences by PCR. DNA was isolated from viruses by HIRT extraction.

[0090]
FIG. 2 shows the effect of these viruses on normal and cancer-derived cell lines. Each cell line was plated and infected at an MOI=20, ˜24h post plating. The cells were then cultured over a period of 17-48 days, and fed every fourth day. The pictures shown in the Figure were taken 7 days after infection. The top row of each section shows the results of cells that were not virally infected (negative control). The middle row shows the results of cells infected with oncolytic adenovirus, in which replication gene E1a is operably linked to the hTERT promoter. The bottom row of each section shows the results of cells infected with adenovirus in which E1a is operably linked to the CMV promoter (positive control). Results are summarized in Table 1.

1TABLE 1Effect of Oncolytic Virus on Cancerous and Non-cancerous CellsUninfectedLysis byLysis bycellphTERT-pCMV-Cell LineOriginCulture ConditionsLysisE1ΔE3E1ΔE3BJforeskin fibroblast90% DMEM/M199 +NONOYES10% FBSIMRlung fibroblast90% DMEM/M199 +NONOYES10% FBSWI-38lung fibroblast90% DMEM/M199 +NONOYES10% FBS +5 μg mL gentamicinA549lung carcinoma90% RPMI +NOYESYES10% FBSAsPC-1adenocarcinoma,90% RPMI +NOYESYESpancreas10% FBSBxPC-3adenocarcinoma,90% EMEM +NOYESYESpancreas10% FBSDAOYmedulloblastoma90% EMEM +NOYESYES10% FBSHeLa:cervical carcinoma90% EMEM +NOYESYES10% FBSHT1080fibrosarcoma90% EMEM +NOYESYES10% FBS

[0091] All cell lines tested were efficiently lysed by AdCMV-E1 dIE3 by day 17 post-infection. All tumor lines were lysed by AdphTERT-E1dIE3 in a similar, but slightly delayed period, while normal lines showed no signs of cytopathic effect and remained healthy out to 6 weeks post-infection.

[0092] The results demonstrate that an oncolytic virus can be constructed by placing a genetic element essential for replication of the virus under control of an hTERT promoter. Replication and lysis occurs in cancer cells, but not in differentiated non-malignant cells.

Example 3

Killing Cancer Cells Using Glycosyltransferase Vectors and Natural Antibody

[0093] Adenovirus vectors comprising encoding sequences for glycosyltransferase under control of the TERT promoter are constructed by cloning the encoding sequence behind the hTERT promoter sequence of pGRN267, as described in Example 1.

[0094] SEQ. ID NO:2 and SEQ. ID NO:4 provide the encoding sequences for the A and B transferase, respectively.

[0095]
FIG. 3 is a comparison of the known mammalian α1,3GT protein sequences, the ABO transferases, and the amino acid translation of the human α1,3GT pseudogene. Based on this comparison and a comparison of the gene sequences, a humanized version of the marmoset α1,3GT protein sequence has been devised (SEQ. ID NO:13). Another α1,3GT sequence has been devised in which the marmoset prototype has been adapted with substitutions in the extracellular domain to enhance activity, based on a consensus of other mammalian α1,3GT amino acid sequences (SEQ. ID NO:12).

[0096]
FIG. 4 provides a listing of a humanized α1,3GT encoding sequence, adapting the marmoset nucleic acid sequence with conservative and silent substitutions in the human pseudogene (SEQ. ID NO:16).

[0097] A model adenovirus vector is made using the sheep α1,3GT encoding sequence shown in SEQ. ID NO:17. Briefly, a EcI136II fragment from a plasmid comprising the cDNA coding sequence plus ˜70 bp of untranslated upstream sequence is cloned into the EcoRI(Klenow blunted)-FseI(Klenow blunted) sites of pGRN267 such that the sheep α1,3GT gene is in the same orientation as the hTERT promoter. Then a Not1-BamHI fragment from the plasmid containing the transcription pause region, the hTERT promoter, the sheep α1,3GT gene sequence and the SV40 polyA signal is cloned into the Not1-BgIII sites of pAdBN (Quantum), which is then made into an adenovirus vector according to the manufacturer's technology.

[0098] Ability of α1,3GT and ABO transferase vectors to promote tumor cell lysis is tested using a panel of established cell lines as in Example 2.

[0099] First, the ABO phenotype of each line is determined by incubating alternate wells with fresh human serum of the A and B blood type at 37° C. for 30-60 min, and measuring trypan blue exclusion.

[0100] Fresh cells are then transduced with the test vectors at a suitable MOI, and cultured in a serum-free medium. Vectors comprising the opposite ABO transferase or α1,3GT under control of the TERT promoter are used to treat the test well. The same transferase under control of the CMV promoter is a positive control. A promoterless vector, a vector comprising ABO matched transferase, and empty vector can all serve as negative controls.

[0101] After 2 or 7 days, the cells are washed, and overlaid with fresh ABO matched human serum. After incubation at 37° C. for 30-60 min, 0.4% trypan blue is added, and the percentage of lysed (blue staining) cells is determined.

SEQUENCE DATA

[0102]

2

TABLE 2

Sequences listed in this Disclosure

SEQ. ID NO:
Designation
Reference

1
Lambda clone designated λGφ5
GenBank Accession AF121948

(ATCC Accession No. 98505)
International Patent Publication

Contains human Telomerase Reverse
WO 00/46355.

Transcriptase (hTERT) genomic insert

(residues 44-15375). The ATG translation

initiation site begins at residue 13545.

2
Human histo blood group A transferase
GenBank Accession J05175

cDNA sequence
See also Accession Nos. AF134413 &

AF134412;

Yamamoto et al., Nature May 17 1990;

345: 229 (1990);

U.S. Pat. No. 5,326,857

3
Human histo blood group A transferase
(supra)

amino acid sequence

4
Human histo blood group B transferase
GenBank Accession AF134414

cDNA sequence
Yamamoto et al., Nature May 17 1990;

345: 229 (1990);

U.S. Pat. No. 5,326,857

5
Human histo blood group B transferase
(supra)

amino acid sequence

6
Marmoset α1,3-galactosyltransferase
GenBank Accession S71333

amino acid sequence
Henion et al., Glycobiology 4,193 (1994)

7
Amino acid translation of human
(infra)

1,3-galactosyltransferase pseudogene

8
Sheep α1,3-galactosyltransferase
Chris Denning & John Clark, Geron Biomed

amino acid sequence

9
Bovine α1,3-galactosyltransferase
GenBank Accession J04989

amino acid sequence
Joziasse et al. “Bovine α1−>3-

galactosyltransferase” J. Biol. Chem. 264,

14290 (1989)

10
Pig α1,3-galactosyltransferase
GenBank Accession L36152

amino acid sequence
Sus scrofa alpha-1,3-galactosyltransferase

mRNA.

Strahan et al. “cDNA sequence and

chromosome localization of pig α1,3

galactosyltransferase” Immunogenetics 41,

101 (1995)

See also GenBank Accession L36535

Sandrin et al. “Characterization of cDNA

clones for porcine a(1,3)galactosyl

transferase” Xenotransplantation (1994)

11
Mouse α1,3-galactosyltransferase
GenBank Accession M26925

amino acid sequence
Larsen et al. “Isolation of a cDNA encoding

a murine UDP galactose: β-D-galactosyl-1,4-

N-acetyl-D-glucosaminide alpha-1,3-

galactosyltransferase” Proc. Natl. Acad.

Sci. USA 86, 8227 (1989)

See also GenBank Accession IM85153

Joziasse et al. “Murine alpha-1,3-

galactosyltransferase: A single gene locus

specifies four isoforms of the enzyme by

alternative splicing” J. Biol. Chem. 267,

5534 (1992)

12
Consensus α1,3-galactosyltransferase
This Invention

amino acid sequence

13
Humanized α1,3-galactosyltransferase
This Invention

amino acid sequence

14
Marmoset α1,3-galactosyltransferase
GenBank Accession S71333

cDNA sequence
Henion et al., Glycobiology 4,193 (1994)

15
Human α1,3-galactosyltransferase
GenBank Accession J05421

pseudogene sequence
Larsen et al., J. Biol. Chem. .265: 7055,

1990

See also GenBank Accession M60263

Joziasse et al. “Characterization of an

alpha-1−>3-galactosyltransferase

homologue on human chromosome 12 that

is organized as a processed pseudogene”

J. Biol. Chem. 266, 6991 (1991)

16
Humanized α1,3-galactosyltransferase
This Invention

encoding sequence

17
Sheep α1,3-galactosyltransferase
Chris Denning & John Clark, Geron Biomed

encoding sequence

[0103]

Glycosyltransferase vectors for treating cancer

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