Background and purpose
Sorafenib, a potent inhibitor that targets several kinases associated with tumourigenesis and cell survival, has been approved for clinical treatment as a single agent. However, combining sorafenib with other agents improves its anti-tumour efficacy in various preclinical tumour models. ABT-263, a second-generation BH3 mimic, binds to the anti-apoptotic family members Bcl-2, Bcl-xL and Bcl-w, and has been demonstrated to enhance TNFSF10 (TRAIL)-induced apoptosis in human hepatocarcinoma cells. Hence, we investigated the effects of ABT-263 treatment combined with sorafenib. Experimental approach: The effects of ABT-263 combined with sorafenib were investigated in vitro, on cell viability, clone formation and apoptosis, and the mechanism examined using western blot and flow cytometry. This combination was also evaluated in vivo, in a mouse xenograft model; tumour growth, volume and weights were measured and a TUNEL assay performed. Key
Purpose
Sorafenib, a potent inhibitor that targets several kinases associated with tumourigenesis and cell survival, has been approved for clinical treatment as a single agent. However, combining sorafenib with other agents improves its anti-tumour efficacy in various preclinical tumour models. ABT-263, a second-generation BH3 mimic, binds to the anti-apoptotic family members Bcl-2, Bcl-xL and Bcl-w, and has been demonstrated to enhance TNFSF10 (TRAIL)-induced apoptosis in human hepatocarcinoma cells. Hence, we investigated the effects of ABT-263 treatment combined with sorafenib. Experimental approach: The effects of ABT-263 combined with sorafenib were investigated in vitro, on cell viability, clone formation and apoptosis, and the mechanism examined using western blot and flow cytometry. This combination was also evaluated in vivo, in a mouse xenograft model; tumour growth, volume and weights were measured and a TUNEL assay performed. Key
Results
ABT-263 enhanced sorafenib-induced apoptosis while sparing non-tumourigenic cells. Although ABT-263 plus sorafenib significantly stimulated intracellular reactive oxygen species production and subsequent mitochondrial depolarization, this was not sufficient to trigger cell apoptosis. ABT-263 plus sorafenib significantly decreased Akt activity, which was, at least partly, involved in its effect on apoptosis. Bax and p21 (CIP1/WAF1) were shown to play a critical role in ABT-263 plus sorafenib-induced apoptosis. Combining sorafenib with ABT-263 dramatically increased its efficacy in vivo.