:
Gastric cancer is one of the most common malignancies worldwide and the third leading cause of cancer-related
death. In the present study, we investigated the potential activity of OSI-027, a potent and selective mammalian target of rapamycin complex 1/2 (mTOR1/2) dual inhibitor, alone or in combination with oxaliplatin against gastric cancer cells in
vitro. Cell counting kit-8 assays and EdU staining were performed to examine the proliferation of cancer cells. Cell cycle
and apoptosis were detected by flow cytometry. Western blot was used to detect the elements of the mTOR pathway and Pgp in gastric cancer cell lines. OSI-027 inhibited the proliferation of MKN-45 and AGS cells by arresting the cell cycle in
the G0/G1 phase. At the molecular level, OSI-027 simultaneously blocked mTORC1 and mTORC2 activation, and resulted
in the downregulation of phosphor-Akt, phpspho-p70S6k, phosphor-4EBP1, cyclin D1, and cyclin-dependent kinase4
(CDK4). Additionally, OSI-027 also downregulated P-gp, which enhanced oxaliplatin-induced apoptosis and suppressed
multidrug resistance. Moreover, OSI-027 exhibited synergistic cytotoxic effects with oxaliplatin in vitro, while a P-gp siRNA knockdown significantly inhibited the synergistic effect. In summary, our results suggest that dual mTORC1/mTORC2
inhibitors (e.g., OSI-027) should be further investigated as a potential valuable treatment for gastric cancer.
