Dimethyl celecoxib sensitizes gastric cancer cells to ABT‐737 via AIF nuclear translocation

Gastric cancer is the fourth most common cancer in the world. The clinical applications of both chemotherapy and targeted drugs are limited because of the complexity of gastric cancer. In this study, sulforhodamine B, colony formation assay, 4',6‐diamidino‐2‐phenylindole (DAPI) stain, flow cytometry were used to determine the in vitro cytotoxicity, apoptosis and mitochondrial membrane potential of gastric cancer AGS and HGC‐27 cells before and after treatment. Real‐time PCR and Western blot were used to analyse the mRNA transcription and protein expression respectively. Confocal microscopy was used to determine the localization of target protein within the cells. Treatment with the combination of ABT‐737 and 2,5‐dimethyl‐celecoxib (DMC) showed strong synergistic effect in both AGS and HGC‐27 cells. Moreover, DMC would not influence the intracellular prostaglandin E2 (PGE2) level, thus lacking the toxicity profile of celecoxib. Interestingly, given the significant synergistic effect, combination treatment did not affect the protein expression of BH‐3 proteins including Puma, Noxa and Bim. In combination treatment, cell apoptosis was found independent of caspase‐3 activation. The translocation of apoptosis‐inducing factor (AIF) from mitochondrion to nuclear was responsible for the induced apoptosis in the combination treatment. Taken together, this study provided a novel combination treatment regimen for gastric cancer. Furthermore, the existence of caspase‐independent apoptotic pathway induced by treatment of ABT‐737 was not yet seen until combined with DMC, which shed light on an alternative mechanism involved in Bcl‐2 inhibitor‐induced apoptosis.