Abstract: Objective To examine the expressions of multidrug resistance gene (MDR)-1 and P-glycoprotein (P-gp) in nasopharyngeal squamous cell carcinoma CNE1 cell line before and after X-ray exposure. Methods CNE1 cells were exposed to X-ray. After the irradiation, the CNE1 cells were cultured for 24 hours and tested. The mRNA expressions of MDR-1 in CNE1 cells were measured by semiquantitative realtime polymerase chain reaction (RT-PCR) before and after X-ray exposure, and the protein expressions of P-gp in CNE1 cells were detected by Western blotting. The protein expressions of Pgp in CNE1 cells were observed by confocal microscope before and after X-ray exposure. Results The results of RT-PCR showed that the absorbance (A) values of MDR1 mRNA in CNE1 cells were 0.17±0.01 and 0.34±0.03 before and after irradiation, and the difference was statistically significant (t=16.541, P＜0.001). The results of Western blotting showed that the A values of P-gp protein in CNE1 cells were 0.02±0.01 and 0.04±0.01, and the difference was statistically significant (t=4.612, P=0.016). The green fluorescence intensity of P-gp protein in CNE1 cells after X-ray irradiation was higher than that before X-ray irradiation by confocal microscope. Conclusion X-ray irradiation can cause the high expressions of MDR-1 and P-gp in CNE1 cells, suggesting that X-ray irradiation can induce the occurrence of multidrug resistance in CNE1 cells.

Key words: Nasopharyngeal neoplasms, CNE1 cells, Drug resistance, multiple, X-ray irradiation