Fas (APO-1/CD95) signaling pathway is intact in radioresistant human glioma cells.

Radiation-induced apoptosis can be mediated through pathways initiated by either DNA damage or ceramide-induced Fas signaling. Glioblastoma multiforme is a primary brain tumor that is highly resistant to irradiation, and U-87 MG, SF126, and T98G are glioblastoma-derived cell lines that mimic this characteristic. We found that these radioresistant glioma cells are susceptible to Fas-mediated cell death induced by treatment with either anti-Fas antibody or exogenous ceramide. Fas-mediated cell death in these cell lines is p53-independent. These data demonstrate that apoptosis can be induced by ceramide and mediated through the Fas pathway in glioma cells, although high-dose ionizing radiation fails to trigger this pathway.