PMAIP1 and glioblastoma: Previous studies reported that apoptosis resistance in GBM cells could be due to the over-expression of inhibitors of apoptosis (Bcl-2, BIRC1, and BCL2L2) and the suppression of apoptosis inducers (BOK, PMAIP1, caspase-6, caspase-7, caspase-8, APAF1) [52].