Combination of metformin and RG7388 enhances inhibition of growth and induction of apoptosis of ovarian cancer cells through the PI3K/AKT/mTOR pathway

Ovarian cancer is a gynecological cancer that has the highest mortality rate and is often resistant to conventional treatments. Therefore, development of new therapies is essential. Metformin (MET), which is the priority drug for treatment of type 2 diabetes, has received increasing attention because of its anti-tumor effects. Here, we examined combined anti-tumor effects of MET and RG7388, the only MDM2 (mouse double minute 2 homolog) antagonist that has entered phase III clinical trials, on ovarian cancer cell lines. We examined effects on proliferation by Cell Counting Kit-8 (CCK-8) and colony formation assays, and effects on apoptosis by flow cytometric analysis and Hoechst staining. Western blotting was used to measure protein expression in cells and tissues treated with MET and/or RG7388. Flow cytometry was used to measure reactive oxygen species (ROS). We also examined the effects of MET and/or RG7388 on inhibition of A2780 cell growth in vivo. The combination of MET and RG7388 significantly increased growth inhibition, apoptosis, and ROS of A2780 and SKOV3 cells compared with either agent alone. Additionally, in vitro and in vivo results showed that MET and/or RG7388 inhibited the phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway and their combination had a stronger effect. Our findings suggest that the combination of MET and RG7388 enhances growth inhibition and apoptosis induction of ovarian cancer cells through the PI3K/AKT/mTOR pathway and accumulation of intracellular ROS. •Combination of metformin and an MDM2 antagonist enhanced the inhibition of ovarian cancer cells proliferation.•The combination of metformin and RG7388 significantly promoted the apoptosis of ovarian cancer cells.•Metformin and RG7388 induced ROS accumulation in ovarian cancer cells.•Metformin combined with RG7388 inhibited PI3K/Akt/mTOR pathway.