Silencing lncRNA HOTTIP affects radiosensitivity of non-small cell lung cancer cell lines by up-regulating miR-663a

Objective: To investigate the effect of lncRNA HOTTIP on the radiosensitivity of four non-small cell lung cancer cell lines cultured in vitro by regulating the expression of miR-663a. Methods: Four non-small cell lung cancer cell lines (H838, H157, A549, and H1299) were irradiated with different radiation intensities (0, 2, 4, 6, and 8 Gy). Cell survival was detected by colony formation assay. The expression levels of HOTTIP and miR-663a were detected by qRT-PCR. A549 and H1299 cells were selected for the subsequent experiment. After silencing HOTTIP and/or over-expressing miR-663a, cell survival was detected by colony formation assay. Cell apoptosis was detected by flow cytometry. The expression levels of Cleaved caspase-3, Cleaved PARP and γ-H₂AX were quantitatively measured by Western blot. The targeting relationship between HOTTIP and miR-663a was verified by dual luciferase reporter assay and qRT-PCR. Results: The expression of HOTTIP was up-regulated, whereas that of miR-663a was down-regulated in the radiation-resistant H157, A549 and H1299 cells. Silencing HOTTIP or over-expressing miR-663a inhibited the survival of A549 and H1299 cells (radiosensitization ratios were 1.562 and 1.507, respectively), promoted the expression of Cleaved caspase-3, Cleaved PARP and γ-H₂AX, and accelerated cell apoptosis induced by radiation exposure. miR-663a was a target gene of HOTTIP, and HOTTIP negatively regulated the expression of miR-663a. The inhibition of miR-663a reversed the effect of silencing HOTTIP on the radiosensitivity of non-small cell lung cancer cells. Conclusion: Silencing HOTTIP can suppress the survival of non-small cell lung cancer cells and promotes cell apoptosis by up-regulating the expression of miR-663a, thereby enhancing the radiosensitivity of non-small cell lung cancer cell lines. (authors)