Interferon- α enhances CD95L-induced apoptosis of human malignant glioma cells

Abstract

CD95 ligand (CD95L)-induced apoptosis is a novel immunotherapeutic approach to malignant glioma. Here, we report that interferon- α (IFN- α) sensitizes LN-229 and T98G human malignant glioma cells to CD95L-induced apoptosis. In contrast to the effects of IFN- γ and TNF- α which sensitize glioma cells to CD95 antibody-induced apoptosis in part by enhancing CD95 expression, IFN- α has no effect on CD95 expression at the cell surface of LN-229 and T98G cells. To confirm that changes in CD95 expression are not required for the effects of IFN- α, we show that IFN- α enhances CD95L-induced apoptosis even in CD95-transfected LN-308 glioma cells. These LN-308 cells have little endogenous CD95 expression but express high levels of CD95 from a stably integrated CD95 expression plasmid. The sensitizing effects of IFN- α appear to be independent of cell cycle effects of IFN- α and are unaffected by ectopic expression of the bcl-2 proto-oncogene. IFN- α enhances CD95L-induced activation of caspase-3, a critical mediator of CD95L-induced cell death. IFN- α also increases the cytotoxic effects of BCNU, teniposide and cytarabine in both cell lines, and of vincristine in LN-229 cells. Doxorubicin and 5-fluorouracil toxicity are unaffected by IFN- α. IFN- α may be a useful adjunct to novel strategies of immunochemotherapy for malignant gliomas that target CD95-mediated apoptosis.