Co-expression of Fas and Fas ligand in human non-astrocytic glial tumors

The study of Fas (APO-1/CD95) and Fas ligand (FasL) expression in human glial neoplasms has been primarily restricted to astrocytomas. Using immunohistochemistry, we analyzed 35 non-astrocytic glial neoplasms (12 WHO grade II ependymomas, 15 grade II oligodendrogliomas, and 8 grade III oligodendrogliomas) for these factors. A significant correlation was found between Fas and FasL expression within the same tumors (P = 0.001). Western blotting was used to corroborate these findings in 7 of these tumors (3 ependymomas and 4 oligodendrogliomas). Theoretically, the co-expression of Fas and FasL should render gliomas susceptible to suicidal and fratricidal elimination. Their progressive nature, however, suggests that gliomas have acquired mechanisms to prevent Fas-mediated apoptosis. Expression of the anti-apoptotic protooncogene bcl-2 is one potential way in which Fas/FasL-bearing gliomas can escape this fate. Although expression of Bcl-2 protein was found in 6 of 12 (50%) grade II ependymomas, 5 of 15 (33%) grade II oligodendrogliomas, and 6 of 8 (75%) grade III oligodendrogliomas, no correlation between Fas/FasL co-expression and Bcl-2 production could be demonstrated, indicating that protection from Fas-mediated apoptosis probably involves other mechanisms. Received: 10 November 1998 / Revised: 15 March 1999 / Accepted: 24 March 1999