MiR‐138 inhibits cell proliferation and reverses epithelial‐mesenchymal transition in non‐small cell lung cancer cells by targeting GIT1 and SEMA4C

Non-small-cell lung cancer (NSCLC) is one of the most common and lethal malignant tumours worldwide with a poor 5-year survival rate. Recent studies indicated that miRNAs have been involved in the tumorigenic driver pathways in NSCLC, but the relevant molecular mechanisms are not well-understood. In this study, we investigated the biological functions and molecular mechanisms of miR-138 in human NSCLC. The effects of miR-138 on the NSCLC cell growth and epithelial-mesenchymal transition (EMT) were first examined. Then the targeting connections of miR-138 with G-protein-coupled receptor kinase-interacting protein 1 (GIT1) and semaphorin 4C (SEMA4C) were confirmed by dual luciferase reporter assays. Finally, the effects of GIT1 and SEMA4C on the NSCLC cell growth and EMT were investigated respectively. We found that the ectopic expression of miR-138 resulted in a significant inhibition of NSCLC growth and reversion of EMT. GIT1 and SEMA4C were identified as two novel targets of miR-138. Furthermore, GIT1 and SEMA4C knockdown inhibited the cell growth and reversed EMT, just like the effects of miR-138 overexpression on NSCLC cells, whereas ectopic expression of GIT1 and SEMA4C partly rescued the suppressive effects of miR-138 in NSCLC cells. These data represent a crucial step towards the understanding of the novel roles and molecular mechanism of miR-138, GIT1 and SEMA4C in NSCLC progression, which may provide some new targets or prognostic biomarkers for NSCLC treatment, thus having implications in translational oncology.