Metformin combined with cisplatin reduces anticancer activity via ATM/CHK2-dependent upregulation of Rad51 pathway in ovarian cancer

Ovarian cancer (OC) is the deadliest malignancy of the female reproductive system. The standard first-line therapy for OC involves cytoreductive surgical debulking followed by chemotherapy based on platinum and paclitaxel. Despite these treatments, there remains a high rate of tumor recurrence and resistance to platinum. Recent studies have highlighted the potential anti-tumor properties of metformin (met), a traditional diabetes drug. In our study, we investigated the impact of met on the anticancer activities of cisplatin (cDDP) both in vitro and in vivo. Our findings revealed that combining met with cisplatin significantly reduced apoptosis in OC cells, decreased DNA damage, and induced resistance to cDDP. Furthermore, our mechanistic study indicated that the resistance induced by met is primarily driven by the inhibition of the ATM/CHK2 pathway and the upregulation of the Rad51 protein. Using an ATM inhibitor, KU55933, effectively reversed the cisplatin resistance phenotype. In conclusion, our results suggest that met can antagonize the effects of cDDP in specific types of OC cells, leading to a reduction in the chemotherapeutic efficacy of cDDP.