CASP9 and glioblastoma: Silencing of Usp9X by siRNA results in down-regulation of Usp9X protein levels, concomitant suppression of Bag3, strong activation of caspase-9/-3 and apoptosis induction (Figure 5C-5D), suggesting that suppression of Usp9X is a pivotal regulator of intrinsic apoptosis and a potent sensitizer for intrinsic apoptotic stimuli in TP53-mutated glioblastoma cells.