Salinomycin and oxaliplatin synergistically enhances cytotoxic effect on human colorectal cancer cells in vitro and in vivo.

Oxaliplatin (OXA) is widely used for colorectal cancer (CRC) as a first-line chemotherapy. However, drug resistance and peripheral neurotoxicity prevail in colorectal cancer therapy. Salinomycin (SAL) makes cancer cells sensitive to ionizing radiation and chemotherapeutic drugs. Chemotherapy regimens that combine more than two drugs can improve the outcome of patients. In the present study, we detected apoptosis and mitochondrial function in CRC cells through MTT assays, Annexin V-FITC/PI staining, colony-forming assays, intracellular reactive oxygen species (ROS) measurements, western blotting and so on. We used CompuSyn software to calculate combination index (CI). The effect of SAL and OXA was synergistic. The combination treatment inhibited cell proliferation, migration and colony formation but increased the expression of proapoptotic proteins and promoted cell apoptosis of CRC cells. In vitro experiments demonstrated that the SAL and OXA cotreatment increased intracellular ROS levels in CRC cell lines, decreased the MMP and activated the mitogen-activated protein kinase (MAPK) pathway, thus inhibiting the proliferation of CRC cells and promoting the apoptosis of CRC cells. Pretreatment with N-acetylcysteine (NAC) reversed this effect. Cotreatment with SAL and OXA increases the apoptotic effects in OXA-treated CRC cell lines. In vivo, combined treatment of SAL and OXA markedly inhibited the tumor growth compared to either drug alone. SAL enhances OXA-induced antitumor effects in CRC both in vitro and in vivo by ROS-mediated mitochondrial apoptosis and activation of the MAPK pathway. These results may provide a rationale for combining SAL with OXA for CRC treatment.