Living T9 glioma cells expressing membrane macrophage colony-stimulating factor produce immediate tumor destruction by polymorphonuclear leukocytes and macrophages via a "paraptosis"-induced pathway that promotes systemic immunity against intracranial T9 gliomas.

Cloned T9-C2 glioma cells transfected with membrane macrophage colony-stimulating factor (mM-CSF) never formed subcutaneous tumors when implanted into Fischer rats, whereas control T9 cells did. The T9-C2 cells were completely killed within 1 day through a mechanism that resembled paraptosis. Vacuolization of the T9-C2 cell's mitochondria and endoplasmic reticulum started within 4 hours after implantation. By 24 hours, the dead tumor cells were swollen and terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL)-positive. Bcl2-transduced T9-C2 cells failed to form tumors in rats. Both T9 and T9-C2 cells produced cytokine-induced neutrophil chemoattractant that recruited the granulocytes into the tumor injection sites, where they interacted with the tumor cells. Freshly isolated macrophages killed the T9-C2 cells in vitro by a mechanism independent of phagocytosis. Nude athymic rats treated with antiasialo GM1 antibody formed T9-C2 tumors, whereas rats treated with a natural killer cell (NK)-specific antibody failed to form tumors. When treated with antipolymorphonuclear leukocyte (anti-PMN) and antimacrophage antibodies, 80% of nude rats formed tumors, whereas only 40% of the rats developed a tumor when a single antibody was used. This suggests that both PMNs and macrophages are involved in the killing of T9-C2 tumor cells. Immunocompetent rats that rejected the living T9-C2 cells were immune to the intracranial rechallenge with T9 cells. No vaccinating effect occurred if the T9-C2 cells were freeze-thawed, x-irradiated, or treated with mitomycin-C prior to injection. Optimal tumor immunization using mM-CSF-transduced T9 cells requires viable tumor cells. In this study optimal tumor immunization occurred when a strong inflammatory response at the injection of the tumor cells was induced.

T9 glioma cells expressing membrane-macrophage colony stimulating factor produce CD4+ T cell-associated protective immunity against T9 intracranial gliomas and systemic immunity against different syngeneic gliomas.

Cloned T9 glioma cells (T9-C2) expressing the membrane form of macrophage colony stimulating factor (mM-CSF) inoculated subcutaneously into rats do not grow and glioma-specific immunity is stimulated. Immunotherapy experiments showed that intracranial T9 tumors present for one to four days could be successfully eradicated by peripheral vaccination with T9-C2 cells. CD4+ and CD8+ T splenocytes from immunized rats, when restimulated in vitro with T9 cells, produced interleukin-2 and -4. Protective immunity against intracranial T9 gliomas could only be adoptively transferred into naive rats by the CD4+ splenocytes obtained from T9-C2 immunized rats. Rats immunized by the T9-C2 tumor cells also resisted two different syngeneic gliomas (RT2 and F98) but allowed a syngeneic NUTU-19 ovarian cancer to grow. Such cross-protective immunity against unrelated gliomas suggests that mM-CSF transfected tumor cells have immunotherapeutic potential for use as an allogeneic tumor vaccine.