Novel chemokine for mobilizing stem cells

Abstract

Novel chemokines for mobilizing stem cells are provided. Methods of mobilizing stem cells are also provided.

Description

BACKGROUND OF THE INVENTION

[0002] Hematopoietic cells have very important roles in a number of different processes in the body. For example, leukocytic hematopoietic cells are important in maintaining the body's defenses against disease; monocytes, macrophages and lymphocytes are involved in potentiating the body's responses to infection and tumors, while granulocytes are involved in overcoming infection, parasites and tumors. Platelets, another hematopoietic cell, form an important element in the hemostatic mechanism through initiating thrombus formation by their adhesion to each other and to damaged surfaces, and by the release of factors which assist in the formation of the fibrin clot. Erythrocytes are mainly involved in the transport of oxygen.

[0003] All of these blood cells are derived from a single progenitor cell called the hematopoietic stem cell. Stem cells are both pluripotent, in that they give rise to all different cell types, and capable of self renewal. Hematopoietic stem cells make up only a small percentage of bone marrow cells and are normally quiescent. However, when stimulated to divide, these stem cells produce a differentiated daughter cell with great proliferative potential. Sequential rounds of division and differentiation give rise to an enormous amplification of cell numbers which is necessary for the production of mature blood cells. This process of division and differentiation is subject to regulation at many levels to control cell production.

[0004] Numerous studies have led to the definition of functions of several hematopoietic regulatory messengers. These biomolecules have been characterized as stimulatory, e.g., Colony Stimulating Factors (CSFs) and interleukins (IL-1, IL-3, IL-5 and IL-9); inhibitory, e.g., transforming growth factor-β (TGF-β), interferon, prostaglandin E, tumor necrosis factor, macrophage inflammatory protein-1 (MIP-1), lactoferrin, acidic isoferritins, acSKDP, and pEEDCK (a synthetic HP5B monomer); or enhancing, e.g., TGF-β, IL-6, IL-4, IL-9, IL-11, MIP-1, MIP-2, leukemia inhibitory factor and Steel factor. Pelus et al., Experimental Hematology 22:239-247 (1994). Stimulatory biomolecules have been found to promote division of particular cell lineages. For example, G-CSF derives neutrophil production, while erythropoietin promotes formation of erythrocytes.

[0005] A number of these biomolecules and additional agents have been found to induce the mobilization of hematopoietic stem cells.

[0006] A single injection of IL-8 has been shown to induce mobilization of pluripotent stem cells that are able to provide permanent reconstitution of myeloid cells and of T and B lymphocytes. Laterveer et al., Blood 85:2269-2275 (1995). IL-8 belongs to a family of pro-inflammatory molecules called chemokines. This family has been divided into two subfamilies, the CXC and CC chemokines, based on whether the first two cysteine residues in a conserved motif are adjacent to each other or are separated by an intervening residue. In general, CXC, which include IL-8, melanoma growth-stimulating activity (MGSA) and platelet factor (PF4), are potent chemoattractants and activators of neutrophils but not monocytes. In contrast, CC chemokines, which include RANTES, monocyte chemotactic protein 1 (MCP-1) and MIP-1, are chemoattractants for monocytes but not neutrophils.

[0007] Stem cell inhibitors (SCIs) such as the CC chemokines, murine and human MIP-1α (LD78), have also been shown to enhance the release and mobilization of cells into the peripheral blood. WO 94/28916; Simm et al., Blood 84:2937 (1994).

[0008] Increased mobilization of stem cells in patients treated with sequentially administered interleukin-3 and GM-CSF compared with GM-CSF alone has been reported by Brugger et al., Blood 79:1193-1200 (1992). In addition, it has been shown that the absolute number of peripheral blood progenitor cells can be expanded in vitro by culture in a cocktail of cytokines, usually including SCF, IL-3, and either IL-6 or IL-1. Bodine, D., Experimental Hematology 23:293-295 (1995).

[0009] SK&F 107647, a hematoregulatory agent containing an ethylene bridge in place of the cysteine bridge of HP5B, has been demonstrated to be a potent simulator of in vitro myelopoiesis. Pelus et al., Experimental Hematology 22:239-247 (1994). Injection of SK&F 107647 in normal mice resulted in a two- to six-fold increase in serum colony-stimulating activity. Administration of this agent over four days resulted in significant increases in the number of granulocyte-macrophage, erythroid, and multipotential progenitor cells, as well as stimulating their cell cycle rates.

[0010] It has also been found that pretreatment with stem cell stimulating factor such as G-CSF can expand the pool of progenitor cells susceptible for mobilization by these agents, further increasing their mobilizing effect. For example, the combination of MIP-1 a with G-CSF was found to increase white cell count in the blood as compared to G-CSF alone. Simm et al., Blood 84:2937 (1994). Co-administration of SCI with G-CSF caused the enhanced mobilization of a number of cell types including neutrophils, monocytes, eosinphils, lymphocytes and basophil. WO 94/28916. Administration of G-CSF alone had no effect on the release of eosinphils or basophils after two days of administration. Similar effects were observed when other agents such as GM-CSF, f-Met-Leu-Phe or IL-8 were coadministered with SCIs.

[0011] New chemokines have now been identified which also mobilize stem cells in an animal. These chemokines can be administered alone, or in combination with a colony stimulating factor or hemoregulatory agent to enhance mobilization of stem cells.

SUMMARY OF THE INVENTION

[0012] An object of the present invention is to provide novel chemokines for the mobilization of stem cells in an animal.

[0013] Another object of the invention is to provide a method of mobilizing stem cells.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 shows the sequence and alignment of the novel chemokines with known chemokines.

DETAILED DESCRIPTION OF THE INVENTION

[0015] In recent years, the availability of recombinant cytokines and the use of hematopoietic stem cell support have resulted in the widespread application of high-dose chemotherapy regimens designed to improve the success of cancer therapy. Despite significant advances, however, delayed recovery of hematopoiesis remains an important source of morbidity and mortality for patients treated with this approach. Since their discovery over 20 years ago, peripheral blood hematopoietic progenitor cells (PBPCs) have been increasingly used to supplement and even replace bone marrow as the source of hematopoietic support in a variety of situations.

[0016] Purified populations of cells are increasingly being used therapeutically and it would therefore be advantageous to be able to increase the number of circulating blood cells. It is useful to be able to harvest hematopoietic cells prior to chemotherapy or radiotherapy, thus, protecting them from harmful effects of this therapy; after therapy, the cells can be returned to the patient. It would therefore be highly beneficial to provide an agent which promoted the release and mobilization of a number of hematopoietic cells. Such an agent would be useful for enhancing the response to infection.

[0017] Peripheral blood cell transplantation is an important procedure in the treatment of cancer patients with high dose chemotherapy. In such treatment, patients are treated to induce clinical remission of their cancer, then during the remission, successive treatment with CSF, for example, by priming with cyclophosphamide then administration of G-CSF, causes eventual mobilization of cells from the bone marrow to the peripheral circulation for harvesting of leukophoresed blood; then the patient is given high dose chemotherapy or radiotherapy and the resultant bone marrow failure is compensated for by infusion of the stored blood or cells collected previously. This procedure may be modified by the omission of the initial induction of remission, and whole blood may be collected rather than leukophoresed blood. The mobilization effects of the present invention makes it a candidate both to replace CSFs in such cancer treatment regimes, and also to complement the mobilization effects of CSFs in combined treatments.

[0018] The two subfamilies of chemokines (CXC and CC) are ever-expanding, and presumably the individual members have similar, if slightly divergent, functions. The chemokines disclosed in the present invention are new members of the CC subfamily and are structurally similar to MPC-1, MPC-3, hRANTES, mMIP-1α, and mMIP-1β (FIG. 1). The effect of these chemokines in inducing leukophilia will find clinical and veterinary application in all utilities where the raising of hematopoietic cell levels is important. For example, a chemokine of the present invention can be used to enhance immune responses against chronic infections, particularly parasitic and bacterial infections. It may also have a role in promoting wound healing.

[0019] The chemoattractant activity of these chemokines can be boosted by pretreatment with a colony stimulating factor such as G-CSF or GM-CSF. Alternatively, the hematoregulatory peptides SK&F 107647 (currently in clinical trials), FLT-3 ligand (Immunex) or any other G-CSF mimetics (peptide and non-peptide) may be used. These stimulants may have an even more dramatic effect on these novel chemokines than on those already known due to their slight structural differences. For example, CKB-6 in combination with G-CSF was effective as a mobilizing factor. As known in the art, these peptides are useful in stimulating myelopoiesis in patients suffering from reduced myelopoietic activity, including bone marrow damage, agranulocytosis and aplastic anemia. Also included are patients who have depressed bone marrow function due to immunosuppressive treatment to suppress tissue reactions (i.e., bone marrow transplant surgery). They may also be used to promote more rapid regeneration of bone marrow after cytostatic chemotherapy and radiation therapy for neoplastic and viral diseases. There may also be a value where patients have serious infections due to a lack of immune response following bone marrow failure.

[0020] The hematopoietic stem cells released and harvested in the manner described above may be useful for subsequent in vitro and ex vivo manipulations to deliver gene products in gene therapy. Another embodiment is co-administration with cytotoxic drugs.

[0021] The following examples are provided for illustrative purposes only and are not intended to limit the invention.

EXAMPLES

Example 1

Mobilization Assay for Novel Chemokines as Single Agents

[0022] A panel of novel chemokines will be tested as individual stem cell mobilization agents in BDF 1 mice. These chemokines include, but should not be limited to: Ckβ-1, Ckβ-4, Ckβ-6, Ckβ-7, Ckβ-8, Ckβ-9, Ckβ-10, Ckβ-11, Ckβ-12, Ckβ-13, and Ckα-1. Each agent will be assayed in concentrations of 50, 10, and 2 μg/mouse and administered via SC, IM, or a PO route. The kinetics of chemokine mobilization of stem cells will be monitored in 15 minute intervals over a period of 60 minutes by collecting blood samples from the mice by cardiac puncture. The mobilized stem cells will be collected by a densing gradient (Lympholyte M.). Cells are washed then frozen for future usage. The mobilization profile of the blood differentials will be assessed using a Technicon HI hematology analyzer. Mobilization of inflammatory cells such as PMNs, eosinophils, and basophils will be taken into account when evaluating the overall potential inflammatory profile. The chemokine IL-8, which mobilizes hematopoietic stem cells as a single factor, will be included in these studies as a positive control.

Example 2

Mobilization Assay for Novel Chemokines in Combination with Hematostimulants

[0023] J In these studies, hematostimulants will be assayed in combination with the aforementioned chemokines as mobilization factors. These agents include: G-CSF, GM-CSF, SK&F 107647, and FLT-3 ligand. However, any G-CSF mimetic (hematostimulants which are not colony stimulating factors like G-CSF or GMCSF, but have hematopoietic activity) may be used. In combination studies, G-CSF will be administered IP to mice four days prior to the novel chemokines. As in Example 1, the dose of chemokine and time of blood collection will be varied. Combination studies with hematostimulant pre-treatment will utilize MIP-1α as the positive control.

Example 3

CFU Assay

[0024] Blood samples collected during the mobilization phase will be assessed for colony forming units (CFU-GM) at days 7 and 14. Cells are adjusted to 2×106 cells/ml in McCoys medium with 15×FBS serum. A single layer agar system utilizing the following is used: McCoys medium enriched with nutrients (NaHCO3, pyruvate, amino acids and vitamins); 0.3% Bacto agar. To this is added cells from the blood samples (final concentration=2×105 cells/ml). The agar plates are incubated at 37° C., 5% CO2 for 7 days. Colonies of proliferating cells (CFU-GM) are counted utilizing a microscope. In addition, early hematopoietic high proliferative potential (HPP) progenitors, will be counted in the day 14 CFU cultures.

Claims

1. A chemokine comprising the amino acid sequence of any one of SEQ ID NOS:1-10, wherein said chemokine is capable of mobilizing stem cells.

2. A method of mobilizing stem cells in an animal comprising administering to an animal and effective amount of a chemokine comprising an amino acid sequence selected from the group consisting of any one of SEQ ID NOS: 1-10.

3. The method of claim 2 further comprising administering a colony stimulating factor.

4. The method of claim 2 further comprising administering a hematoregulatory agent.