[en] Objective: To investigate the effect of elemene on the radiosensitivity of A549 cells and its possible molecular mechanism. Methods: The effect of radiosensitivity was detected by colony forming assay. The protein expressions of DNA-PKcs, Bcl-2 and P53 were detected with Western blot. The correlation between the protein expression of DNA-PKcs and Bcl-2, DNA-PKcs and P53 was analyzed. Results: Elemene had radiosensitizing effect on A549 cells, with the SER_D0 and SER_Dq 1.54 ± 0.20 and 1.43±0.15, respectively for 10 μg/ml elemene, and 1.63 ±0.32 and 1.75 ±0.19, respectively for 20 μg/ml elemene. Compared with irradiation group, the expression of DNA-PKcs was reduced significantly in 10, 20 μg/ml elemene combined with radiation group (t=7.52, 8.33, P<0.05), so was for Bcl-2 (t=10.74, 11.33, P<0.05). The expression of P53 protein increased significantly (t=-9.25, 7.66, P<0.05). There was a remarkable negative correlation between the expression of DNA-PKcs and P53 (r=-0.569, P<0.05), and a remarkable positive correlation between DNA-PKcs and Bcl-2 (r=0.755, P<0.05 ). Conclusions: Elemene has radiosensitizing effect on A549 cells, which might be related to down-regulation of DNA-PKcs gene expression, up-regulation of P53 and down-regulation of Bcl-2. (authors)