Melatonin reverses nasopharyngeal carcinoma cisplatin chemoresistance by inhibiting the Wnt/beta-catenin signaling pathway.

Cisplatin (DDP)-based concurrent chemo-radiotherapy is a standard approach to treat locoregionally advanced nasopharyngeal carcinoma (NPC). However, many patients eventually develop recurrence and/or distant metastasis due to chemoresistance. In this study, we aimed to elucidate the effects of melatonin on DDP chemoresistance in NPC cell lines in vitro and vivo, and we explored potential chemoresistance mechanisms. We found that DDP chemoresistance in NPC cells is mediated through the Wnt/beta-catenin signaling pathway. Melatonin not only reversed DDP chemoresistance, but also enhanced DDP antitumor activity by suppressing the nuclear translocation of beta-catenin, and reducing expression of Wnt/beta-catenin response genes in NPC cells. In vivo, combined treatment with DDP and melatonin reduced tumor burden to a greater extent than single drug-treatments in an orthotopic xenograft mouse model. Our findings provide novel evidence that melatonin inhibits the Wnt/beta-catenin pathway in NPC, and suggest that melatonin could be applied in combination with DDP to treat NPC.