Abstract: Objective The aim of this study was to investigate the mechanism of miR-616 enhancing the radiosensitivity of lung cancer cells by targeting TIMP-2.Methods Lung cancer HCC827 cells were routinely cultured and HCC827 cells were irradiated with X-rays as the RI group,which emitted at a fixed dose rate of 4 Gy/min;the energy classification of X-rays used to irradiate the cells was 8 Gy,and the incubation time was 24 h.HCC827 cells were transfected with miR-616-shRNA as the miR-616 inhibitor group.HCC827 cells were transfected with miR-616-shRNA and then were used X-ray irradiation by X-ray generator as the miR-616 inhibitor + RI group.The above cells were cultured for 72 hours,and six replicates were set in each dose.At the end of the experiment,MTT assay was used to determine cell proliferation,Giemsa staining was used to determine the colony percentage,flow cytometry was used to determine apoptosis and distribution of cell cycle,Transwell chamber was used to determine cell invasion,RT-PCR and Western blot were used to determine the expression miR-616 and TIMP-2 genes at levels of mRNA and protein.Results Compared with the HCC827 cells group,the OD values,survival rate,number of clone formation,number of transmembrane cells,the level of miR-616 mRNA in the RI group,miR-616 inhibitor group,and miR-616 inhibitor + RI group were reduced(P＜0.05).Compared with the RI group and the miR-616 inhibitor group,the OD values,survival rate,number of clone formation,number of membrane cells,and the level of miR-616 mRNA in the miR-616 inhibitor + RI group were decreased(P＜0.05).Compared with the HCC827 cells group,apoptotic rates,the cell cycle at the G1 phase,and the expression of TIMP-2 at levels of mRNA and protein in the RI group,miR-616 inhibitor group,and miR-616 inhibitor + RI group were increased(P＜0.05).Compared with the RI group and miR-616 group,apoptotic rates,the cell cycle at the G1 phase,and the expression of TIMP-2 at levels of mRNA and protein in the miR-616 inhibitor + RI group were increased(P＜0.05).Conclusion The down-regulated expression of miR-616 can enhance the radiosensitivity of lung cancer cells in vitro,and then enhance the radiation-mediated inhibition of tumor viability,cell apoptosis induced and cell cycle arrested.The mechanism may be related to the inhibition of miR-616,which can promote the related expression of TIMP-2 gene and protein.

Key words: MicroRNA-616, TIMP-2, Lung cancer cells, Radiosensitivity