ABSTRACT:Objective To investigate the differential gene expression of nasopharyngeal carcinoma cell line CNE-2 and CNE-2R exposed to X-rays.Methods We used neutral comet assay to detect the intrinsic radiosensitiv-ity of tumor cells,immunofluorescence to detect the phosphorylated histone γH2AX and Rad5 1 foci formation and to assay the time-dose effects on cell radiation injury and radiation radiosensitivity change after irradiation.The dif-ferential gene expression was screened with cDNA microarray by DNA damage repair related gene chip.Differenti-ally expressed proteins screened were confirmed by Western blot.Results After 2 h of 4 Gy 9MeV-β-ray irradia-tion,CNE-2R cells had aggravated DNA damage compared to CNE-2 cells and the damage was more obvious with the prolongation of time.It suggested that cell DNA damage severity was more obvious.The immunofluorescence showed the positive rates ofγH2AX cells in CNE-2 cell line were higher than those in CNE-2R cell line.There were 37 different genes related to DNA damage repair in CNE-2 cell line compared with CNE-2R cell line,while 24 up-regulated and 13 down-regulated genes were found in SiHaR cells.In them,there were 6 genes whose ratios were 6 times higher and 3 genes whose ratios were lower than 0.1.Western blot verified the results of four differentially expressed proteins compared with CNE-2 cells,in which GADD45a and RRAD1 expression levels were significantly lowered in CNE-2R while the RAD9a and RCF2 protein significantly increased.Conclusion The radioresistance of CNE-2R cells is significantly related to DNA damage repair capacity in certain mutations at the gene level.It is possible to regulate cell radiosensitivity by regulating the related gene.