Effects of miRNA-21 expression on radio-sensitivity of NSCLC cell. A, Elevated miRNA-21 was observed after γ- ray radiation with a dose of 6 Gy, and its level was highest at 8 hours. B, A549 cells were transfected with miRNA-21 RNAi and scrambled RNAi vector. Expression of miRNA-21 was detected in 48 hours after transfection miRNA-21 level decreased in RNAi cells. C, Cells were exposed to various doses of IR (0 Gy, 2 Gy, 4 Gy, 6 Gy and 8 Gy) at a rate of 2.4 Gy/min 48 hours after transfection, then clonogenic assay was performed. Knock-down of miRNA-21 promoted the radio-sensitivity of A549 cells,*p<0.05.