CRM-A, BCL-2 AND NDGA INHIBIT CD95L-INDUCED APOPTOSIS OF MALIGNANT GLIOMA-CELLS AT THE LEVEL OF CASPASE-8 PROCESSING

Susceptibility to CD95 (Fas/APO-1)-mediated apoptosis in human glioma cells depends on CD95 expression and unknown factors that regulate sig nal transduction, Thus, LN-18 cells are highly sensitive to CD95 ligan d (CD95L) whereas LN-229 cells require coexposure to inhibitors of RNA or protein synthesis for induction of apoptosis, Here, we report that caspase 8 and 3 activation, poly(ADP-ribose)polymerase cleavage and a poptosis are inhibited by the lipoxygenase inhibitor, nordihydroguaret ic acid (NDGA), or ectopic expression of crm-A or bcl-2, CD95L-induced glioma cell apoptosis does not involve ceramide generation. Apoptosis induced by exogenous ceramide resembles CD95-mediated apoptosis in th at bcl-2 is protective but differs in that NDGA and crm-A have no effe ct and in that cycloheximide (CHX) inhibits rather than potentiates ce ramide-induced cell death. We conclude that caspase 8 and caspase 3 ac tivation, but not ceramide generation, are required for CD95 ligand-in duced apoptosis of glioma cells and that bcl-2, crm-A and NDGA all act upstream of caspases to inhibit apoptosis.