ING5 belongs to the inhibitor of growth (ING) candidate tumor suppressor family, which is involved in multiple cellular functions, such as cell cycle regulation, apoptosis, and chromatin remodelling. Previously, we reported that ING5 overexpression inhibits EMT by regulating EMT-related molecules, including Snail1, at the mRNA and protein levels. However, the mechanisms remain unclear. In the current study, we identify that ING5 overexpression induces the upregulation of miR-34c-5p. The expression levels of both ING5 and miR-34c-5p in NSCLC tissues from the TCGA database are decreased compared with that in adjacent tissues. Higher expression levels of both ING5 and miR-34c-5p predict longer overall survival (OS). Snail1 is the target gene of miR-34c-5p, as predicted by an online database, which is further verified by a dual-luciferase reporter assay. The expression level of Snail1 in NSCLC cells is markedly reduced following miR-34c-5p overexpression, leading to the inactivation of the Snail1 downstream TGF-β/Smad3 signaling pathway. The TGF-β signaling-specific inhibitor LY2157299 reverses the enhanced EMT, proliferation, migration, and invasion abilities induced by the miR-34c-5p inhibitor. Furthermore, tail vein injection of miR-34c-5p agomir inhibits xenografted tumor metastasis. Overall, this study concludes that miR-34c-5p, induced by ING5 overexpression, is a tumor suppressor that targets Snail1 and mediates the inhibitory effects of ING5 on the EMT and invasion of NSCLC cells. These results provide a novel mechanism mediating the antitumor effects of ING5.
Keywords: inhibitor of growth protein 5 (ING5), miR-34c-5p; non-small cell lung cancer (NSCLC), invasion and metastasis, diagnostic and prognostic biomarkers.