Objective To study the role Erk/Slug signal pathway in the radiosensitivity of MDAMB-231 cells.Methods MDA-MB-231 cells were transfected with NF-κBp65 siRNA,PUMA siRNA and Slug siRNA respectively or treated with U0126 for 24h,then the cells were irradiated with 4 Gy γ-ray.At different time points post-irradiation,the expressions of Erk1/2,NF-κBp65,Slug and PUMA protein were detected.The cell survival rate and apoptotic index were detected by MTT and TUNEL methods.Resluts Compared with 4 Gy irradiated group,the expression of PUMA was reduced in NF-κB p65 siRNA/4 Gy group,the expressions of Slug and Erk1/2 were obviously decreased but PUMA increased in U0126/4 Gy group,the expression of Erk1/2 had no change but the expression of PUMA increased significantly in Slug siRNA/4 Gyγ group.Meanwhile,at 48h post-irradiation,for U0126/4 Gy group and Slug siRNA/4 Gy group,cells survival rates were decreased to 19.78 ±2.71 (F=11.39,P＜0.05) and 17.41 ±4.58(F=15.31,P＜0.05),cell apoptosis rates were 28.61 ±4.70 (F=9.84,P＜0.05) and 27.55±6.41(F =10.31,P ＜ 0.05),respectively.At 24 h post-irradiation,for NF-κB p65 siRNA/4 Gy group and PUMA siRNA/4 Gy group,cell survival rates approached to 85.65 ± 9.60 (F =12.31,P ＜ 0.05) and 87.53±11.50 (F=13.68,P＜0.05),and cell apoptosis rates declined to 3.28 ±0.78 (F=10.83,P ＜ 0.05) and 3.46 ± 0.84 (F =9.92,P ＜ 0.05).Conclusions The radiosensitivity of MDA-MB-231cells was relative to the induction of NF-κB up-regulated PUMA,and the radioresistance was caused by the up-regulation of Slug induced by Erk1/2,which inhibited the expression of PUMA.