The injection of irradiated tumor cells genetically engineered to express the granolocyte macrophage-colony stimulating factor (GM-CSF) is reported as stimulating antitumoral immunity in several animal models. We used the 9L gliosarcoma rat model to investigate the potency of this strategy in relation to the central nervous system. After in vitro transduction experiments to generate 9L murine cells producing GM-CSF (9LmGM-CSF cells), we found that with the exception of one rat subcutaneously (s.c.) grafted with 108 9LmGM-CSF cells, syngenic rats s.c. injected (dorsal route) with 106-108 viable 9LmGM-CSF cells did not develop s.c. 9L gliosarcomas, while rats s.c. grafted with the same number of naive 9L cells died between 25 and 45 days postgraft. Intracerebral stereotactic injections of 4.104 naive 9L (without s.c. 9LmGM-CSF treatment) killed all the rats within 18-24 days, while s.c. grafting with 108 9LmGM-CSF cells wholly prevented the development of 9L brain gliosarcomas. These results outline the feasibility of the GM-CSF gene transfer approach in glioma (or at least gliosarcoma) gene therapy and could therefore serve as a basis for the development of an adjuvant treatment of glioblastomas using GM-CSF-producing tumor cell vaccines.

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