OSI-027 Alleviates Oxaliplatin Chemoresistance in Gastric Cancer Cells by Suppressing P-gp Induction

Area of Science:

• Oncology
• Molecular Biology
• Pharmacology

Background:

• Gastric cancer is a leading cause of cancer death globally.
• Targeting the mammalian target of rapamycin (mTOR) pathway is a promising strategy for cancer therapy.
• Multidrug resistance (MDR) mediated by P-glycoprotein (P-gp) is a significant challenge in gastric cancer treatment.

Purpose of the Study:

• To investigate the anti-cancer activity of OSI-027, a dual mTORC1/2 inhibitor, against gastric cancer cells.
• To evaluate the combination therapy of OSI-027 and oxaliplatin in gastric cancer.
• To explore the effects of OSI-027 on cell proliferation, cell cycle, apoptosis, and P-gp expression in gastric cancer.

Main Methods:

• In vitro experiments using gastric cancer cell lines (MKN-45 and AGS).
• Cell counting kit-8 and EdU staining for proliferation assessment.
• Flow cytometry for cell cycle and apoptosis analysis.
• Western blot to analyze mTOR pathway components and P-gp.
• Combination treatment with OSI-027 and oxaliplatin, with and without P-gp siRNA.

Main Results:

• OSI-027 inhibited gastric cancer cell proliferation by inducing G0/G1 cell cycle arrest.
• OSI-027 effectively blocked both mTORC1 and mTORC2 signaling, downregulating key proteins like Akt, p70S6k, 4EBP1, cyclin D1, and CDK4.
• OSI-027 suppressed P-gp expression, enhancing oxaliplatin-induced apoptosis and overcoming MDR.
• A synergistic cytotoxic effect was observed between OSI-027 and oxaliplatin, which was dependent on P-gp.

Conclusions:

• Dual mTORC1/mTORC2 inhibition with OSI-027 demonstrates significant anti-cancer activity in gastric cancer cells.
• OSI-027 potentiates the efficacy of oxaliplatin by downregulating P-gp and overcoming multidrug resistance.
• These findings support the further investigation of dual mTOR inhibitors like OSI-027 as a potential therapeutic strategy for gastric cancer.