Abt-737 enhances apoptosis of gastric cancer cells induced by MCL-1 small-molecule inhibitor UMI-77 / 中国药理学通报

ABSTRACT

Aim: To investigate the promoting effect of Bcl-2/Bcl-xL inhibitor ABT-737 on apoptosis of gastric cancer cells induced by small molecule Mcl-1 inhibitor UMI-77, and to explore its possible mechanism. Methods: The response of gastric cancer MGC-803 and HGC-27 cells to different concentrations of UMI-77 was detected by MTS assay. In the UMI-77-resistant cell lines, the effect of treatment with UMI-77/ABT-737 alone or in combination on cell viability was detected by MTS assay. The apoptotic rate and the changes of the mitochondrial membrane potential were analyzed by flow cytometry. The cleavage of caspase-9, caspase-3 and PARP-1, as well as the expression level of Bcl-2 family members and IAP proteins, were determined by Western blot. Results: Compared with MGC-803 cells, HGC-27 cells were resistant to UMI-77. Treatment with ABT-737 alone in HGC-27 cells also induced minimal level of cell death. While treatment with both agents induced much greater decreased cell viability. All the dead cells were positive for Annexin V and mitochondrial membrane potential collapsed. Caspase-9, caspase-3 and its substrate PARP-1 were cleaved. All of these proved that the sensitization effect was achieved by activating the mitochondrial apoptotic pathway. Protein levels of XIAP, cIAP1 and cIAP2 decreased after treatment with UMI-77 plus ABT-737. It also resulted in the increase of NOXA and Bcl-2 along with the decline of PUMA and Mcl-1. Conclusions: The combination of UMI-77 and ABT-737 could significantly increase the sensitivity of gastric cancer cells to the Mcl-1 small molecule inhibitor UMI-77.