ABT-737 promotes tBid mitochondrial accumulation to enhance TRAIL-induced apoptosis in glioblastoma cells

Abstract

To search for novel strategies to enhance the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis pathways in glioblastoma, we used the B-cell lymphoma 2/Bcl2-like 2-inhibitor ABT-737. Here we report that ABT-737 and TRAIL cooperate to induce apoptosis in several glioblastoma cell lines in a highly synergistic manner (combination index c and second mitochondria-derived activator of caspase (Smac) into the cytosol and caspase activation are strongly increased in cotreated cells. Of note, knockdown of Bid significantly decreases ABT-737- and TRAIL-mediated Bax activation and apoptosis. Also, caspase-3 silencing reduces ABT-737- and TRAIL-induced Bid cleavage and apoptosis, indicating that a caspase-3-driven, mitochondrial feedback loop contributes to Bid processing. Importantly, ABT-737 profoundly enhances TRAIL-triggered apoptosis in primary cultured glioblastoma cells derived from tumor material, underlining the clinical relevance. Also, ABT-737 acts in concert with TRAIL to suppress tumor growth in an in vivo glioblastoma model. In conclusion, the rational combination of ABT-737 and TRAIL cooperates to trigger tBid mitochondrial accumulation and apoptosis. This approach presents a promising strategy for targeting the apoptosis pathways in glioblastoma, which warrants further investigation.