RESUMO
Cell-based gene therapy after cytokine gene transfer is being investigated for autologous and allogeneic vaccination in cancer therapy. Here we show that mice vaccinated with 3-5 x 10(6) interleukin 12 (IL-12) gene-transduced CT26 colon cancer cells developed a long-lasting antitumor immune memory able to reject not only parental cells but also syngeneic, LM3 mammary, and MCE fibrosarcoma tumorigenic cells. In contrast, mice vaccinated with 0.5-1 x 10(6) CT26 cells transduced with pBabe neo IL-12 retrovirus cells (CT26-IL12) were only able to reject parental cells. An increase in the total circulating levels of IgG2a and a clear shift toward a systemic Th1 response developed, regardless of the amount of injected CT26-IL12 cells. On the contrary, a strong increase in anti-CT26-specific IgG2a levels was observed only when 3-5 x 10(6) CT26-IL12 cells were injected. Immunocompetent mice vaccinated with 3-5 x 10(6) CT26-IL12 cells developed local nodules for a few days, which then ceased growing. These nodules comprised mainly blood vessels, suggesting that an angiogenic process was taking place. CD8+ T cells were responsible for the anti-LM3 tumor cell memory, whereas CD4+ T cells were not involved. Splenocytes and lymphocytes obtained from mice immunized against CT26 cells were able to kill LM3 cells in vitro. Adoptive transfer of lymphocytes obtained from animals immunized against CT26 colon cancer cells suppressed LM3 mammary tumor growth in tumor-bearing mice. The present studies raised the possibility of isolating CTL clones and identifying CTL epitopes shared by different tumor cell types, which can be a target for cancer therapy.
Assuntos
Vacinas Anticâncer/imunologia , Neoplasias do Colo/imunologia , Neoplasias do Colo/terapia , Fibrossarcoma/terapia , Interleucina-12/imunologia , Neoplasias Mamárias Experimentais/terapia , Animais , Especificidade de Anticorpos , Linfócitos T CD8-Positivos/imunologia , Vacinas Anticâncer/genética , Vacinas Anticâncer/uso terapêutico , Neoplasias do Colo/genética , Neoplasias do Colo/prevenção & controle , Fibrossarcoma/imunologia , Fibrossarcoma/prevenção & controle , Técnicas de Transferência de Genes , Imunoglobulina A/sangue , Imunoglobulina G/sangue , Memória Imunológica/imunologia , Imunoterapia Adotiva/métodos , Interleucina-12/genética , Linfócitos/imunologia , Neoplasias Mamárias Experimentais/imunologia , Neoplasias Mamárias Experimentais/prevenção & controle , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Neovascularização Patológica/imunologia , Células Th1/imunologia , Transdução GenéticaRESUMO
Tumor cells transduced with retrovirus carrying the herpes simplex-1 virus thymidine kinase (HSV-tk) are capable of transforming the antiviral drug ganciclovir (GVC) into a metabolic form only toxic to dividing cells. The efficiency of this suicide gene therapy is increased by a "bystander" effect resulting not only in the death of the recipient cell, but also in the death of non modified surrounding cells. Even though the mechanism of this "bystander" effect remains to be elucidated, strong evidence suggest that the immune system plays a main role to achieve complete tumor eradication. In the present study we evaluate the efficiency of this suicide system on three different tumor models: one human melanoma, one murine melanoma, and a rat glioblastoma. Tumors were established by injection of tumor cells s.c. in nude and C57Bl/6 mice, respectively, and stereotactically into the brain of Sprague Dawley rats. Animals in the treated group were co-injected with packaging cells producing recombinant retrovirus carrying the HSV-tk gene, and followed by i.p. administration of GVC. In short term studies, we observed inhibition of tumor growth for all the tumor models evaluated (p < 0.01). In long term studies, using the C6 rat glioma line, 50% of the animals survived longer than 75 days (p < 0.0001), and were able to reject a contralateral challenges with C6 parental cells. Histological and immunohistochemical analysis showed the presence at an inflammatory infiltrate composed by T lymphocytes, macrophages and polymorphonuclear cells. These data demonstrate that suicide genes might represent an attractive form of cancer gene therapy in the treatment of brain tumors and their intracerebral dissemination.