Abstract
OBJECTIVE: To investigate the effect of dihydroartemisinin (DHA) for enhancing the inhibitory effect of cisplatin (DDP) on DDP-resistant nasopharyngeal carcinoma cell line HNE1/DDP and explore the mechanism. METHODS: CCK-8 method was used to assess the survival rate of HNE1/DDP cells treated with DHA (0, 5, 10, 20, 40, 80, and 160 μmol/L) and DDP (0, 4, 8, 16, 32, 64, 128 μmol/L) for 24 or 48 h, and the combination index of DHA and DDP was calculated using Compusyn software. HNE1/DDP cells treated with DHA, DDP, or their combination for 24 h were examined for cell viability, proliferation and colony formation ability using CCK-8, EdU and colony-forming assays. Flow cytometry was used to detect cell apoptosis and intracellular reactive oxygen species (ROS). The expression levels of apoptosis-related proteins cleaved PARP, cleaved caspase-9 and cleaved caspase-3 were detected by Western blotting. The effects of N-acetyl-cysteine (a ROS inhibitor) on proliferation and apoptosis of HNE1/DDP cells with combined treatment with DHA and DDP were analyzed. RESULTS: Different concentrations of DHA and DDP alone both significantly inhibited the viability of HNE1/DDP cells. The combination index of DHA (5 μmol/L) combined with DDP (8, 16, 32, 64, 128 μmol/L) were all below 1. Compared with DHA or DDP alone, their combined treatment more potently decreased the cell viability, colony-forming ability and the number of EdU-positive cells, and significantly increased the apoptotic rate, intracellular ROS level, and the expression levels of cleaved PARP, cleaved caspase-9 and cleaved caspase-3 in HNE1/DDP cells. N-acetyl-cysteine pretreatment obviously attenuated the inhibitory effect on proliferation and apoptosis-inducing effect of DHA combined with DDP in HNE1/DDP cells (P<0.01). CONCLUSION: DHA enhances the growth-inhibitory and apoptosis-inducing effect of DDP on HNE1/DDP cells possibly by promoting accumulation of intracellular ROS.