APAF1 and glioma: Multiple molecular aberrations contribute to TRAlL-resistance of glioma, such as lower expression of caspase-8 [82], overexpression of c-FLIP [71], Bcl-2 [25] and Bcl-xL [63] or loss or structural alterations of TRAIL-R1, TRAIL-R2, Apaf-1, Smac and Bid [49, 97].