Silencing LncRNA OIP5-AS1 increases radiosensitivity of non-small cell lung cancer A549 cell line by up-regulating miR-34c-5p expression

Objective: To investigate the effect of LncRNA OIP5-AS1 on radiosensitivity of non-small cell lung cancer (NSCLC) cells and its mechanism. Methods: The radiation-resistant cell A549R was established by using A549 cells irradiated by X-ray 6Gy in 5 fractions. The expression levels of OIP5-AS1 and miR-34c-5p in A549 and A549R cells were detected by qRT-PCR. OIP5-AS1 inhibitor or miR-34c-5p mimetic was transfected into A549R cells, or OIP5-AS1 overexpression plasmid was transfected into A549 cells. Cell apoptosis was detected by flow cytometry. Cell radiosensitivity was analyzed by colony formation assay. The expression levels of p-Chk2 and p-ATM proteins were measured by Western blot. Dual luciferase assay was adopted to verify the relationship between OIP5-AS1 and miR-34c-5p. Results: Compared with A549 cells, the expression of OIP5-AS1 was significantly up-regulated in A549R cells (1.97 ± 0.11 vs. 1.01 ± 0.05, P < 0.05), whereas the expression of miR-34c-5p was remarkably down-regulated (0.43 ± 0.02 vs. 1.02 ± 0.06, P < 0.05). The expression levels of p-Chk2 and p-ATM proteins in A549R cells in the silencing OIP5-AS1 + 6Gy group were significantly lower (0.43 ± 0.03 vs. 1.39 ± 0.15, 0.51 ± 0.05 vs. 1.21 ± 0.11, both P < 0.05), whereas the apoptotic rate was significantly higher than those in the silencing control + 6Gy group [(13.29 ± 1.25)% vs. (28.47 ± 2.31)%, P < 0.05)]. The expression levels of p-Chk2 and p-ATM proteins in A549 cells in overexpressing OIP5-AS1 + 6 Gy group were significantly higher than those in overexpression control + 6 Gy group (1.23 ± 0.13 vs. 0.75 ± 0.06, 1.08 ± 0.11 vs. 0.59 ± 0.04, both P < 0.05). Inhibiting miR-34c-5p expression reversed the effect of silencing OIP5-AS1 on survival fraction of A549R cells (SER = 1.42). OIP5-AS1 negatively regulated the expression of miR-34c-5p. Conclusion: Silencing OIP5-AS1 enhances the radiosensitivity of radiation-resistant A549 cells by up-regulating the expression of miR-34c-5p, providing a potential target for radiotherapy of NSCLC cells. (authors)