Abstract: bjective To investigate the effect of nuclear apoptosis⁃inducing factor 1 (NAIF1) on the radiosensitivity of nasopharyngeal carcinoma (NPC) CNE⁃2R cells. Methods The expression levels of NAIF1 in NPC CNE⁃2 and CNE⁃2R cells were detected by Western blot. CNE⁃2R cells were infected with overexpressed NAIF1 lentivirus (LV⁃NAIF1 group) and its negative control lentivirus (LV⁃NC group) respectively. The mRNA and protein expression levels of NAIF1 were detected by RT⁃qPCR and Western blot. The CCK⁃8 assay and colony formation assay were performed to evaluate the proliferation and colony formation ability in each group of cells under different doses of irradiation (0, 2, 4, 6, 8 Gy) and the corresponding survival fractions were calculated. The cell cycle distributions of cells before and after exposure to 6 Gy of X⁃ray in each group were analyzed by flow cytometry. Results Compared with CNE⁃2 cells, the protein expression level of NAIF1 was significantly decreased in CNE⁃2R cells (P<0.001). Compared with the LV⁃NC group, the mRNA and protein expression levels of NAIF1 in CNE⁃2R cells were significantly increased in the LV⁃NAIF1 group (all P<0.001). After different doses of irradiation, overexpressed NAIF1 inhibited the proliferation ability of CNE⁃2R cells (P<0.05), and significantly decreased the colony formation number and survival fraction of CNE⁃2R cells (P<0.05). After irradiation with 6 Gy, compared with the LV⁃NC group, overexpressed NAIF1 made more CNE⁃2R cells arrest in the G2/M phase which was the most radiosensitive phase of a cell cycle (P<0.01).   Conclusions NAIF1 is down⁃regulated in NPC CNE⁃2R cells. The overexpression of NAIF1 may enhance the radiosensitivity of NPC CNE⁃2R cells by inhibiting cell proliferation and arresting the cell cycle at the G2/M phase.

Key words:  Nasopharyngeal carcinoma, Nuclear apoptosis-inducing factor 1（NAIF1）, Radiosensitivity