Abstract
MicroRNAs (miRNAs) as small non-coding RNAs act as either tumor suppressors or oncogenes in human cancers, of which miR-149-5p (miR-149) is involved in tumor growth and metastasis, but its role and molecular mechanisms underlying osteosarcoma growth are poorly understood. The correlation of miR-149 expression with clinicopathological characteristics and prognosis in patients with sarcoma was analyzed by The Cancer Genome Atlas (TCGA) RNA-sequencing data. Osteosarcoma cell growth affected by miR-149 was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and colony formation assays. As a result, we found that the expression level of miR-149 was markedly downregulated in human sarcoma samples and were negatively associated with tumor size, acting as an independent prognostic factor for overall survival of the sarcoma patients. Restoration of miR-149 expression suppressed osteosarcoma cell growth, while its knockdown reversed these effects. Furthermore, we identified TNFRSF12A (TNF receptor superfamily member 12A), also called fibroblast growth factor-inducible 14 (Fn14) as a direct target of miR-149, and TNFRSF12A and its ligand TNFSF12 (TNF superfamily member 12), also called tumor necrosis factor-related weak inducer of apoptosis (TWEAK), were both negatively correlated with miR-149 expression in sarcoma samples. Knockdown of TNFRSF12A suppressed cell growth, but its overexpression weakened the antiproliferative effects of miR-149 via the PI3K/AKT (AKT serine/threonine kinase) signaling pathway. Altogether, our findings show that miR-149 functions as a tumor suppressor in osteosarcoma via inhibition of the TWEAK-Fn14 axis and represents a potential therapeutic target in patients with osteosarcoma.