The role of autophagy in the radiosensitivity of the radioresistant human nasopharyngeal carcinoma cell line CNE-2R

PURPOSE: The present study aimed to study the role of autophagy in the radiosensitivity of the radioresistant human nasopharyngeal carcinoma cell line CNE-2R. METHODS: Before being irradiated, CNE-2R cells were treated with the autophagy inhibitor chloroquine diphosphate (CDP) or the autophagy inducer rapamycin (RAPA). Microtubule-associated protein light chain 3 (LC3-II) and p62 were assessed using Western blotting analysis 48 hours after CNE-2R cells were irradiated. The percentage of apoptotic cells was assessed via flow cytometry. CNE-2R cell viability was evaluated using the Cell Counting Kit-8 (CCK8). The radiosensitivity of cells was assessed via clone formation analysis. RESULTS: The level of autophagy in CNE-2R cells improved as the radiation dose increased, reaching the maximum at a dose of 10 Gy. Autophagy was most significantly inhibited by 60 µmol/L CDP in CNE-2R cells, but was obviously enhanced by 100 nmol/L RAPA. Compared with the irradiation (IR) alone group, in the IR + CDP group, autophagy was significantly inhibited, viability was low, the rate of radiation-induced apoptosis was increased, and radiosensitivity was upregulated. In contrast, cells of the IR + RAPA group exhibited greater autophagy, higher viability, a lower rate of radiation-induced apoptosis, and downregulated radiosensitivity. CONCLUSION: The autophagy level is negatively correlated with radiosensitivity for the radio-resistant human nasopharyngeal carcinoma cell line CNE-2R.