Omeprazole improves chemosensitivity of gastric cancer cells by m(6)A demethylase FTO-mediated activation of mTORC1 and DDIT3 up-regulation

The curative effect for patients with advanced gastric cancer is still unsatisfactory. Proton pump inhibitors could be a promising treatment strategy that could sensitize gastric cancer cells to antitumor drugs further; however, the underlying molecular mechanism remains to be further elucidated. In this research, it was found that omeprazole pretreatment could enhance the inhibitory effect of 5-Fu, DDP and TAX on gastric cancer cells. Interestingly, omeprazole pretreatment enhanced the total m(6)A level of cells due to the decreased FTO. TCGA analysis showed that FTO expression is up-regulated in GC tissues and is negatively correlated with disease-free survival of GC patients. It was also found that FTO inhibition induced by omeprazole enhanced the activation of mTORC1 signal pathway that inhibited the prosurvival autophagy so as to improve the antitumor efficiency of chemotherapeutic drugs on GC cells. Meanwhile, transcript level of DDIT3, which is an apoptosis-related tumor suppressor gene downstream of mTORC1, was regulated by omeprazole-induced FTO silence through an m(6)A-dependent mechanism. The present study, for the first time, found that m(6)A modification and its eraser FTO may play a role in the improvement of chemosensitivity mediated by proton pump inhibitor omeprazole.