A novel circ_MACF1/miR-942-5p/TGFBR2 axis regulates the functional behaviors and drug sensitivity in gefitinib-resistant non-small cell lung cancer cells.

BACKGROUND: Resistance to gefitinib remains a major obstacle for the successful treatment of non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) mutations. In this paper, we studied the precise actions of circular RNA (circRNA) microtubule actin crosslinking factor 1 (circ_MACF1) in gefitinib resistance.

METHODS: We established gefitinib-resistant NSCLC cells (PC9/GR and A549/GR). The levels of circ_MACF1, microRNA (miR)-942-5p, and transforming growth factor beta receptor 2 (TGFBR2) were gauged by quantitative real-time PCR (qRT-PCR) or western blot. Subcellular fractionation and Ribonuclease R (RNase R) assays were done to characterize circ_MACF1. Cell survival, proliferation, colony formation, apoptosis, migration, and invasion were detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), 5-Ethynyl-2'-Deoxyuridine (EdU), colony formation, flow cytometry, and transwell assays, respectively. Dual-luciferase reporter assays were used to verify the direct relationship between miR-942-5p and circ_MACF1 or TGFBR2. The xenograft assays were used to assess the role of circ_MACF1 in vivo.

RESULTS: Circ_MACF1 was down-regulated in A549/GR and PC9/GR cells. Overexpression of circ_MACF1 repressed proliferation, migration, invasion, and promoted apoptosis and gefitinib sensitivity of A549/GR and PC9/GR cells in vitro, as well as inhibited tumor growth under gefitinib in vivo. Circ_MACF1 directly targeted miR-942-5p, and miR-942-5p mediated the regulatory effects of circ_MACF1. TGFBR2 was identified as a direct and functional target of miR-942-5p. Circ_MACF1 modulated TGFBR2 expression through miR-942-5p.

CONCLUSION: Our findings demonstrated that circ_MACF1 regulated cell functional behaviors and gefitinib sensitivity of A549/GR and PC9/GR cells at least partially by targeting miR-942-5p to induce TGFBR2 expression.