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Augmentation of Immuno-Gene Therapy for Lung Cancer Using Chemotherapy
TUMOR VACCINES 570. Genetic Vaccination Against Yersinia pestis Using Recombinant Adenovirus Vectors Expressing the V Antigen Maria Chiuchiolo,1 Barry Shea,1 Julie L. Boyer,1 Neil R. Hackett,1 Ronald G. Crystal.1 1 Weill Medical College of Cornell University, New York, NY. Aerosolization of Yersinia pestis in a bioterrorism event would cause the pneumonic form of plague, a virulent, rapidly fatal disease that develops within a few days of exposure. At present, no Y. pestis vaccines are available in the USA. In a bioterror-induced outbreak, an effective vaccine must have a rapid onset of immunity with a single dose to prevent secondary cases. The V antigen of Y. pestis is a component of the type III secretory system that injects virulence factors into host cells; it is known that protective immune responses are elicited against V antigen when administered as purified protein, but multiple immunizations are required for efficacy. In the context that replication-defective adenovirus (Ad)-based gene transfer vectors encoding pathogen-specific antigens can stimulate strong immune responses without a requirement for repeat administration, we examined the immune responses generated against V antigen by immunization with an Ad vaccine vector encoding V antigen with mammalian preferred codons. Two vectors were constructed, AdV expressing the native V antigen sequence and AdsecV expressing a V gene fused to the human Igκ signal sequence for extracellular secretion. At 24 hr post-infection of A549 cells with AdsecV, V antigen could be detected in the culture media by Western analysis and in intracellular organelles by indirect immunofluorescence. We tested the hypothesis that anti-V immunity could be obtained by administration of these vectors to mice and that the secreted version would facilitate antigen uptake by antigen presenting cells and therefore be more efficient at inducing a humoral immune response. To compare anti-V antigen antibody titers evoked by each vaccine, BALB/c mice were immunized with a single intramuscular administration of either vector at a dose of 108 and 109 particles units (pu). At 2 wk post-immunization, the anti-V antigen IgG reciprocal titers in serum from AdV-immunized mice (n=5/group) were 280 ±60 and 3500± 900 for the 108 pu and 109 pu vaccine doses, respectively. In contrast, the anti-V antigen IgG reciprocal titers from AdsecV-immunized mouse sera were 3000± 400 (108 pu) and 9700± 3200 (109 pu). By 4 wk post-immunization, anti-V antigen IgG reciprocal titers were comparable in mice immunized with either AdsecV [2886±410 (108 pu), 3800±420 (109 pu)] or AdV [1600±300 (108 pu), 1800±420 (109 pu)]. The two vectors were also analyzed for stimulation of TH1 (IFN-γ) responses by ELISPOT. Ten days after intramuscular immunization with 109 pu AdV or AdsecV, CD4+ T cells were purified and were stimulated for 36 hr with syngeneic dendritic cells pulsed with purified recombinant V antigen. Antigen-specific IFN-γ producing CD4+ cells were observed for AdsecV-immunized mice (176±16 IFNγ+ / 105 CD4+ T cells) and for AdV mice (95±37 IFNγ + cells/105 CD4 cells). In conclusion, both vaccines can elicit robust humoral as well as cellular immune responses, but secreted V antigen stimulates a more rapid humoral response relative to the cell-associated protein.
TUMOR VACCINES 571. Expression of IL-27 in Murine Carcinoma Cells Produces T Cell-Dependent and Independent Antitumor Effects Masatoshi Tagawa,1 Masako Chiyo,1,2 Osamu Shimozato,1 Ling Yu,1 Takehiko Fujisawa.2 1 Division of Pathology, Chiba Cancer Center Research Institute, Chiba, Japan; 2Department of Thoracic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan. Interleukin (IL)-27 is a recently identified heterodimeric cytokine and is composed of p28, a newly identified IL-12p35-related protein, and Epstein-Barr virus-induced gene 3 (EBI3), an IL-12p40-related protein. IL-27 is produced primarily from activated dendritic cells and induces proliferation of naive but not memory CD4-positive T cells. It also synergizes with IL-12 in interferon (IFN)-γ production from naive T and natural killer (NK) cells. WSX-1/TCCR, one of the IL-27 receptor (R) molecules, is highly expressed in lymphoid organs particularly in naive CD4-positive T and NK cells, and the IL-27/WSX-1 signaling induces the T-bet transcription factor and IL-12Rβ2 expression. These data suggest that IL-27 play a crucial role in the initiation of type 1 helper T cell differentiation before the IL-12/IL-12R system and can augment cell-mediated immunity. We constructed p28-internal ribosomal entry site-EBI3 cDNA (IL-27) and found that IL-27 secreted from COS-7 cells induced both IL12Rβ1 and IL-12Rβ2 expression, and production of IFN-γ from naive spleen cells. We then examined whether Colon 26 murine colon carcinoma cells that were retrovirally transduced with the IL27 gene (Colon 26/IL-27) could produce antitumor effects in inoculated mice. Although proliferation in vitro of Colon 26/IL-27 cells was not different from that of parent cells, syngeneic BALB/c mice rejected Colon 26/IL-27 tumors inoculated and subsequently acquired tumor-specific protective immunity. The antitumor effects were dependent on the amounts of IL-27 secreted. In contrast, mice inoculated with Colon 26 cells transduced with either the p28 or EBI3 gene developed tumors and survival of the mice remained the same as that of the mice inoculated with parent cells. Syngeneic nude mice developed Colon 26/IL-27 tumors but the growth was retarded compared with that of parent tumors. Depletion of NK cells from nude mice with anti-asialo GM1 Ab diminished the growth retardation of Colon 26/IL-27 tumors. Survival of severe combined immunodeficiency (SCID) mice that received subcutaneous inoculation of Colon 26/IL-27 cells was not different from that of the SCID mice inoculated with parent cells. Antibody-mediated depletion showed that IFN-γ was produced from CD4-positive and CD8-positive T, and NK cells of the mice that rejected Colon 26/IL27 tumors. Cytotoxic activity against Colon 26 cells but not irrelevant tumor cells was also detected from the mice. These data collectively suggest that expressed IL-27 in tumors produces T cell-dependent and -independent antitumor effects and is a possible therapeutic strategy for cancer.
572. Augmentation of Immuno-Gene Therapy for Lung Cancer Using Chemotherapy Eiji Suzuki,1 Veena Kapoor,1 Arminder S. Jassar,1 Andrew Haas,1 Larry R. Kaiser,1 Steven M. Albelda.1 1 Thoracic Oncology Research Laboratories, University of Pennsylvania, Philadelphia, PA. RATIONALE: We reported that adenovirus-mediated murine IFNbeta (Ad.muIFN-beta) transfer eradicates murine malignant mesothelioma via a CD8+ T cell-dependent mechanism. However, Ad.muIFN-beta was much less effective in a minimally immunogenic model of lung cancer (LC), Lewis Lung Carcinoma (LLC). We hypothesized that combining chemotherapy (to induce cancer cell
Molecular Therapy Volume 9, Supplement 1, May 2004 Copyright The American Society of Gene Therapy
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TUMOR VACCINES death and increase antigen availability) with Ad.muIFN-beta would be more effective. We used the drug gemcitabine (gem) since it is one of the most effective cytotoxic agents for human LC and has recently been reported to spare T-cell function. METHODS: C57BL/6 mice bearing flank LLC tumors (tumor volumes: 80-100 mm3) were injected intra-tumorally (IT) with 1x109 pfu of Ad.muIFN-beta with or without intra-peritoneal injection with 120 µg/g gem. Chemotherapy was given either 5 days before or after gene therapy. Effects of depletion of CD4+, CD8+ , and NK cells were examined after antibody depletion. To determine if cancer cell death was important, we generated a gem-resistant LLC line by slowly increasing gem concentrations in media. NK cell activity was measured using a Cr51 release assay (Target cell: Cr51 labeled YAC-1, Effector cell: spleen cells from tumor bearing mice treated with gem, Ad.muIFN-beta or the combination) and cytolytic T-lymphocyte (CTL) activity from splenocytes was assessed using in vivo Winn assays. To explore mechanisms of the gem effect, we performed adhesion assays. A mouse endothelial cell line (H5V) was treated with gem for 24 hrs and isolated spleen cells labeled with Cr51 were then allowed to adhere on the test cells for 3 hrs. RESULTS: IT injection of either Ad.muIFN-beta or gem alone had minimal anti-tumor activity in this model. In contrast, combination treatment had significant antitumor activity, but only if gem was given after Ad.muIFN-beta. The combination worked equivalently in gem-resistant LLC suggesting the effect was not dependent on gem-induced tumor cell death, but was due to immunological effects. This was supported by experiments showing: 1) the anti-tumor effects were abolished by NK cell depletion; 2) elimination of CD8+ T cells did not effect initial anti-tumor effects, but blocked growth inhibition during later time points. CD4+ T cell depletion had no effect. Further studies showed that NK cells were activated by Ad.muIFN-beta. Winn assay showed that CD8+ T cells from mice 8 days after the combination treatment had LLC cell lytic activity, while CD8+ T cells from mice 4 days after the combination treatment were not lytic. Adhesion assays showed that significantly higher numbers of splenocytes adhered to H5V cells treated with gem. CONCLUSIONS: Our data suggests that although IT injection of Ad.muIFN-beta activates NK cell activity, the activated NK cells could only effectively enter the tumor site and subsequently induce a CD8+ T cell response if the tumor endothelium was “activated” by gem. This study shows an example of synergy between chemotherapy and immuno-gene therapy and suggests a novel mechanism by which this occurs. A better understanding of this process will lead to improved design of future clinical trials.
573. Immuno Gene Therapy of Feline Fibrosarcoma Using Intratumoral Magnetofection for Gene Delivery – Preliminary Results of a Veterinary Clinical Study Ulrike Schillinger,1 Niels Kjaergaard,2 Kathrin Wiedmann,2 Anne Loecher,2 Stefanie Schlemmer,2 Bianca Schwarz,1 Tina Kempf,1 Johannes Hirschberger,2 Roberto Koestlin,3 Christian Plank,1 Bernd Gansbacher,1 Thomas Brill.1 1 Institute of Experimental Oncology, Technical University Munich, Munich, Germany; 2Dept. of Veterinary Internal Medicine, Ludwig-Maximilian University, Munich, Germany; 3Dept. of Veterinary Surgery, Ludwig-Maximilian University, Munich, Germany. Feline fibrosarcoma is one of the most common feline tumors. It arises spontaneously, is rarely metastatic and relapses within 6 months after standard therapy (surgical resection) in 75 % of the cases. This makes it an ideal model for evaluating immunostimulatory therapeutic strategies. Moreover, besides aggressive surgical excision no effective and versatile treatment is available. Here we report preliminary results from a comparative clinical S216
study where the genes for human IL-2, feline IFN-γ, or human GMCSF, respectively, alone or in combination, were administered. The study design is prospective, randomized, placebo-controlled (= standard therapy) and comprises five arms: (1) standard therapy, i.e. surgery alone; (2) administration of adenovirus coding for IL-2/ IFN-γ or (3) IFN-γ alone into the tumor bed after surgery; (4) presurgical intra-tumoral injection of adenovirus coding for IL-2/ IFN-γ and (5) nonviral Magnetofection of the human GM-CSF gene into the tumor before surgery. The procedure included phase I dose finding studies for the gene therapy groups followed by a phase II comprising 20 patients per group. Preliminary clinical endpoint is relapse-free survival for one year. Magnetofection, which has been developed in our laboratory, is the association of vectors with magnetic particles and gene delivery under the influence of a magnetic field (Scherer et al. 2002, Gene Ther. 9:102-109; Plank et al. 2003, Biol. Chem. 384:737-747). It was applied here in order to achieve improved retention of the injected vector dose in the tumor and in order to eventually achieve better tissue penetration by the vector. Plasmid DNA with the GM-CSF gene under the control of the CMV promoter was associated with polyethylenimine-coated magnetic particles (chemicell, Berlin, Germany), and a dose corresponding to 1250 µg DNA in a volume of 500 µl saline was administered twice in a one week interval prior to surgery into the biologically active margins of the fibrosarcoma. A neodymium-iron-boron permanent magnet was fixed on the tumor adjacent to the injection sites during one hour after vector injection. Pre- and postsurgical diagnosis included monitoring for toxicity, fever, blood cell count, for some treatments serum cytokine levels and evaluation of cytokine expression in tumors. The expression of the cytokine genes was demonstrated for all treatments. All gene-therapeutic treatments led to prolonged relapse-free survival (one year time points: 50 % for postsurgical adenovirus administrations into the tumor bed, 37 % for presurgical intratumoral adenovirus administrations, and 52 % for presurgical Magnetofection versus 23 % for surgery alone). Among the evaluated treatments Magnetofection is the most versatile, most cost-effective, and most relevant in veterinary practise as it avoids the legally required safety precautions associated with the use of recombinant viruses. With further patients admitted to the study, long-term follow-up will warrant a profound assessment of the benefits of this treatment.
574. Systemic IL-12 Eliminates Pre-Established Leukemia in a Murine Model of Philadelphia Chromosome Positive Acute Lymphoblastic Leukemia Tanja A. Gruber,1 Dianne C. Skelton,1 Karen Pepper,1 Denise Peterson,1 Donald B. Kohn.1 1 Bone Marrow Transplant and Research Immunology, Childrens Hospital Los Angeles, Los Angeles, CA. Acute Lymphoblastic Leukemia (ALL) is the most frequent type of leukemia in children and represents roughly 30% of all childhood malignancies. With current chemotherapy protocols event-free survival in children with ALL has reached 75%. The 25% of patients who relapse can often be predicted based on certain prognostic factors including infants less than one year of age and/or the presence of the Philadelphia chromosome (Ph+). Our laboratory has established a murine model of Ph+ ALL utilizing a cell line, BM185, generated by the transformation of Balb/c bone marrow with the Bcr-Abl oncogene. Balb/c mice injected with as few as one thousand BM185 cells die within three to four weeks of challenge, with heavy tumor burdens in the blood, spleen, and bone marrow. Irradiated BM185 cells transduced with various immunomodulators including CD80, CD40 Ligand, and GM-CSF, are able to initiate anti-leukemic immune responses, and can prevent the development of leukemia in Molecular Therapy Volume 9, Supplement 1, Ma y 2004
Copyright The American Society of Gene Therapy
TUMOR VACCINES 571. Expression of IL-27 in Murine Carcinoma Cells Produces T Cell-Dependent and Independent Antitumor Effects Masatoshi Tagawa,1 Masako Chiyo,1,2 Osamu Shimozato,1 Ling Yu,1 Takehiko Fujisawa.2 1 Division of Pathology, Chiba Cancer Center Research Institute, Chiba, Japan; 2Department of Thoracic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan. Interleukin (IL)-27 is a recently identified heterodimeric cytokine and is composed of p28, a newly identified IL-12p35-related protein, and Epstein-Barr virus-induced gene 3 (EBI3), an IL-12p40-related protein. IL-27 is produced primarily from activated dendritic cells and induces proliferation of naive but not memory CD4-positive T cells. It also synergizes with IL-12 in interferon (IFN)-γ production from naive T and natural killer (NK) cells. WSX-1/TCCR, one of the IL-27 receptor (R) molecules, is highly expressed in lymphoid organs particularly in naive CD4-positive T and NK cells, and the IL-27/WSX-1 signaling induces the T-bet transcription factor and IL-12Rβ2 expression. These data suggest that IL-27 play a crucial role in the initiation of type 1 helper T cell differentiation before the IL-12/IL-12R system and can augment cell-mediated immunity. We constructed p28-internal ribosomal entry site-EBI3 cDNA (IL-27) and found that IL-27 secreted from COS-7 cells induced both IL12Rβ1 and IL-12Rβ2 expression, and production of IFN-γ from naive spleen cells. We then examined whether Colon 26 murine colon carcinoma cells that were retrovirally transduced with the IL27 gene (Colon 26/IL-27) could produce antitumor effects in inoculated mice. Although proliferation in vitro of Colon 26/IL-27 cells was not different from that of parent cells, syngeneic BALB/c mice rejected Colon 26/IL-27 tumors inoculated and subsequently acquired tumor-specific protective immunity. The antitumor effects were dependent on the amounts of IL-27 secreted. In contrast, mice inoculated with Colon 26 cells transduced with either the p28 or EBI3 gene developed tumors and survival of the mice remained the same as that of the mice inoculated with parent cells. Syngeneic nude mice developed Colon 26/IL-27 tumors but the growth was retarded compared with that of parent tumors. Depletion of NK cells from nude mice with anti-asialo GM1 Ab diminished the growth retardation of Colon 26/IL-27 tumors. Survival of severe combined immunodeficiency (SCID) mice that received subcutaneous inoculation of Colon 26/IL-27 cells was not different from that of the SCID mice inoculated with parent cells. Antibody-mediated depletion showed that IFN-γ was produced from CD4-positive and CD8-positive T, and NK cells of the mice that rejected Colon 26/IL27 tumors. Cytotoxic activity against Colon 26 cells but not irrelevant tumor cells was also detected from the mice. These data collectively suggest that expressed IL-27 in tumors produces T cell-dependent and -independent antitumor effects and is a possible therapeutic strategy for cancer.
572. Augmentation of Immuno-Gene Therapy for Lung Cancer Using Chemotherapy Eiji Suzuki,1 Veena Kapoor,1 Arminder S. Jassar,1 Andrew Haas,1 Larry R. Kaiser,1 Steven M. Albelda.1 1 Thoracic Oncology Research Laboratories, University of Pennsylvania, Philadelphia, PA. RATIONALE: We reported that adenovirus-mediated murine IFNbeta (Ad.muIFN-beta) transfer eradicates murine malignant mesothelioma via a CD8+ T cell-dependent mechanism. However, Ad.muIFN-beta was much less effective in a minimally immunogenic model of lung cancer (LC), Lewis Lung Carcinoma (LLC). We hypothesized that combining chemotherapy (to induce cancer cell
Molecular Therapy Volume 9, Supplement 1, May 2004 Copyright The American Society of Gene Therapy
S215
TUMOR VACCINES death and increase antigen availability) with Ad.muIFN-beta would be more effective. We used the drug gemcitabine (gem) since it is one of the most effective cytotoxic agents for human LC and has recently been reported to spare T-cell function. METHODS: C57BL/6 mice bearing flank LLC tumors (tumor volumes: 80-100 mm3) were injected intra-tumorally (IT) with 1x109 pfu of Ad.muIFN-beta with or without intra-peritoneal injection with 120 µg/g gem. Chemotherapy was given either 5 days before or after gene therapy. Effects of depletion of CD4+, CD8+ , and NK cells were examined after antibody depletion. To determine if cancer cell death was important, we generated a gem-resistant LLC line by slowly increasing gem concentrations in media. NK cell activity was measured using a Cr51 release assay (Target cell: Cr51 labeled YAC-1, Effector cell: spleen cells from tumor bearing mice treated with gem, Ad.muIFN-beta or the combination) and cytolytic T-lymphocyte (CTL) activity from splenocytes was assessed using in vivo Winn assays. To explore mechanisms of the gem effect, we performed adhesion assays. A mouse endothelial cell line (H5V) was treated with gem for 24 hrs and isolated spleen cells labeled with Cr51 were then allowed to adhere on the test cells for 3 hrs. RESULTS: IT injection of either Ad.muIFN-beta or gem alone had minimal anti-tumor activity in this model. In contrast, combination treatment had significant antitumor activity, but only if gem was given after Ad.muIFN-beta. The combination worked equivalently in gem-resistant LLC suggesting the effect was not dependent on gem-induced tumor cell death, but was due to immunological effects. This was supported by experiments showing: 1) the anti-tumor effects were abolished by NK cell depletion; 2) elimination of CD8+ T cells did not effect initial anti-tumor effects, but blocked growth inhibition during later time points. CD4+ T cell depletion had no effect. Further studies showed that NK cells were activated by Ad.muIFN-beta. Winn assay showed that CD8+ T cells from mice 8 days after the combination treatment had LLC cell lytic activity, while CD8+ T cells from mice 4 days after the combination treatment were not lytic. Adhesion assays showed that significantly higher numbers of splenocytes adhered to H5V cells treated with gem. CONCLUSIONS: Our data suggests that although IT injection of Ad.muIFN-beta activates NK cell activity, the activated NK cells could only effectively enter the tumor site and subsequently induce a CD8+ T cell response if the tumor endothelium was “activated” by gem. This study shows an example of synergy between chemotherapy and immuno-gene therapy and suggests a novel mechanism by which this occurs. A better understanding of this process will lead to improved design of future clinical trials.
573. Immuno Gene Therapy of Feline Fibrosarcoma Using Intratumoral Magnetofection for Gene Delivery – Preliminary Results of a Veterinary Clinical Study Ulrike Schillinger,1 Niels Kjaergaard,2 Kathrin Wiedmann,2 Anne Loecher,2 Stefanie Schlemmer,2 Bianca Schwarz,1 Tina Kempf,1 Johannes Hirschberger,2 Roberto Koestlin,3 Christian Plank,1 Bernd Gansbacher,1 Thomas Brill.1 1 Institute of Experimental Oncology, Technical University Munich, Munich, Germany; 2Dept. of Veterinary Internal Medicine, Ludwig-Maximilian University, Munich, Germany; 3Dept. of Veterinary Surgery, Ludwig-Maximilian University, Munich, Germany. Feline fibrosarcoma is one of the most common feline tumors. It arises spontaneously, is rarely metastatic and relapses within 6 months after standard therapy (surgical resection) in 75 % of the cases. This makes it an ideal model for evaluating immunostimulatory therapeutic strategies. Moreover, besides aggressive surgical excision no effective and versatile treatment is available. Here we report preliminary results from a comparative clinical S216
study where the genes for human IL-2, feline IFN-γ, or human GMCSF, respectively, alone or in combination, were administered. The study design is prospective, randomized, placebo-controlled (= standard therapy) and comprises five arms: (1) standard therapy, i.e. surgery alone; (2) administration of adenovirus coding for IL-2/ IFN-γ or (3) IFN-γ alone into the tumor bed after surgery; (4) presurgical intra-tumoral injection of adenovirus coding for IL-2/ IFN-γ and (5) nonviral Magnetofection of the human GM-CSF gene into the tumor before surgery. The procedure included phase I dose finding studies for the gene therapy groups followed by a phase II comprising 20 patients per group. Preliminary clinical endpoint is relapse-free survival for one year. Magnetofection, which has been developed in our laboratory, is the association of vectors with magnetic particles and gene delivery under the influence of a magnetic field (Scherer et al. 2002, Gene Ther. 9:102-109; Plank et al. 2003, Biol. Chem. 384:737-747). It was applied here in order to achieve improved retention of the injected vector dose in the tumor and in order to eventually achieve better tissue penetration by the vector. Plasmid DNA with the GM-CSF gene under the control of the CMV promoter was associated with polyethylenimine-coated magnetic particles (chemicell, Berlin, Germany), and a dose corresponding to 1250 µg DNA in a volume of 500 µl saline was administered twice in a one week interval prior to surgery into the biologically active margins of the fibrosarcoma. A neodymium-iron-boron permanent magnet was fixed on the tumor adjacent to the injection sites during one hour after vector injection. Pre- and postsurgical diagnosis included monitoring for toxicity, fever, blood cell count, for some treatments serum cytokine levels and evaluation of cytokine expression in tumors. The expression of the cytokine genes was demonstrated for all treatments. All gene-therapeutic treatments led to prolonged relapse-free survival (one year time points: 50 % for postsurgical adenovirus administrations into the tumor bed, 37 % for presurgical intratumoral adenovirus administrations, and 52 % for presurgical Magnetofection versus 23 % for surgery alone). Among the evaluated treatments Magnetofection is the most versatile, most cost-effective, and most relevant in veterinary practise as it avoids the legally required safety precautions associated with the use of recombinant viruses. With further patients admitted to the study, long-term follow-up will warrant a profound assessment of the benefits of this treatment.
574. Systemic IL-12 Eliminates Pre-Established Leukemia in a Murine Model of Philadelphia Chromosome Positive Acute Lymphoblastic Leukemia Tanja A. Gruber,1 Dianne C. Skelton,1 Karen Pepper,1 Denise Peterson,1 Donald B. Kohn.1 1 Bone Marrow Transplant and Research Immunology, Childrens Hospital Los Angeles, Los Angeles, CA. Acute Lymphoblastic Leukemia (ALL) is the most frequent type of leukemia in children and represents roughly 30% of all childhood malignancies. With current chemotherapy protocols event-free survival in children with ALL has reached 75%. The 25% of patients who relapse can often be predicted based on certain prognostic factors including infants less than one year of age and/or the presence of the Philadelphia chromosome (Ph+). Our laboratory has established a murine model of Ph+ ALL utilizing a cell line, BM185, generated by the transformation of Balb/c bone marrow with the Bcr-Abl oncogene. Balb/c mice injected with as few as one thousand BM185 cells die within three to four weeks of challenge, with heavy tumor burdens in the blood, spleen, and bone marrow. Irradiated BM185 cells transduced with various immunomodulators including CD80, CD40 Ligand, and GM-CSF, are able to initiate anti-leukemic immune responses, and can prevent the development of leukemia in Molecular Therapy Volume 9, Supplement 1, Ma y 2004
Copyright The American Society of Gene Therapy