miR-548b inhibits the proliferation and invasion of malignant gliomas by targeting metastasis tumor-associated protein-2.

microRNAs (miRNAs) play important roles in cancer development and progression. In this study, we explored the expression and biological roles of miR-548b in human gliomas. The expression of miR-548b in human glioma tissues and cell lines was examined. Gain-of-function experiments were conducted to determine the roles of miR-548b in glioma cell growth, invasiveness, and tumorigenesis. Bioinformatic analysis and luciferase reporter assays were performed to identify direct target genes for miR-548b. miR-548b was underexpressed in human glioma tissues and cell lines. Re-expression of miR-548b significantly inhibited the proliferation and colony formation of U87 and U373 glioma cells. Enforced expression of miR-548b significantly impaired the invasiveness of glioma cells. Notably, metastasis tumor-associated protein-2 (MTA2) was a direct target of miR-548b. Overexpression of miR-548b negatively regulated endogenous MTA2 expression in U87 cells. Rescue experiments with an MTA2 construct lacking the 3'-untranslated region showed that enforced expression of MTA2 significantly restored cell proliferation and invasion in miR-548b-overexpressing cells. In-vivo studies confirmed that miR-548b overexpression retarded the growth of U87 xenograft tumors, which was accompanied by reduced expression of MTA2. In conclusion, miR-548b exerts its tumor-suppressive activity in glioma through repression of MTA2. Restoration of miR-548b may have therapeutic potential in glioma.