Abstract: Objective The aims of this study were to establish a radioresistant human lung cancer cell line H1975R,and to explore the role of miR-17 in the formation of radioresistance.Methods The lung cancer radioresistant cell line H1975R was established in vitro by continuous irradiation with gradient dose.The radiosensitivity of H1975R and H1975 cells was verified by colony formation assay.We determined the expression levels of miR-17 in parental cells and radioresistant cells by quantitative RT-PCR and The expression of miR-17 was up-regulated or down-regulated,and the changes in radiosensitivity were compared.Cell proliferation was detected by CCK-8 assay.Flow cytometry was performed to determine apoptosis and cycle distribution.Results The radiobiological parameters(D₀,N,D_q and SF₂)of H1975R cells were greater than those in the H1975 cells(P＜0.05),indicating a stronger radioresistance.From the Results of RT-PCR,the expression level of miR-17 in H1975R cells was 2.67 times than that in H1975 cells(P＜0.01).After up-regulating expression of miR-17 in H1975 cells,its radiosensitivity was reduced,but the proliferation,anti-apoptosis and the proportion of cells in the G₂/M phase increased(P＜0.05).Similarly,after down-regulating expression of miR-17 in H1975R cells,the radiosensitivity increased,while the cell proliferation and anti-apoptosis ability decreased,and the proportion of cells in the G₂/M phase decreased(P＜0.05).Conclusion miR-17 is involved in the regulation of radioresistance in non-small cell lung cancer,which may become a new target for the treatment of radioresistance.

Key words: Non-small cell lung cancer, Radioresistance, Proliferation, Apoptosis, miR-17