MiR-205 functions as a tumor suppressor via targeting TGF-α in osteosarcoma

Osteosarcoma (OS) is the most common primary bone cancer, and it is most prevalent in children and young adults. The prognosis of OS remains poor, and survival of OS reached a plateau. The discovery of microRNAs (miRNAs) provides a new possibility for the early diagnosis and treatment of OS. In this study, we detected the expression level of miR-205 and Transforming growth factor-alpha (TGF-α) in 15 cases of clinical OS tissues and adjacent normal bone tissues. We found that the expression of miR-205 was significantly lower in OS tissues than in normal bone tissues; the expression of TGF-α mRNA was significantly increased in OS tissues than in normal bone tissues, the miR-205 was negatively correlated with TGF-α levels in both OS and normal bone tissues. Functional studies demonstrated that miR-205 significantly decreased the capability of cell proliferation, invasion and migration and induced G0/G1 growth arrest and apoptosis in OS cells. By using bioinformatics analytic tool (Targetscan), the 3'UTR of TGF-α gene was found to be a target of miR-205. Luciferase report assay further confirmed that TGF-α 3'UTR is a direct target of miR-205. We also found that the expression of TGF-α mRNA and protein was significantly down-regulated or up-regulated after miR-205 mimic or miR-205 inhibitor transfection. TGF-α knockdown study further showed that miR-205 regulated cell proliferation, invasion and migration by targeting TGF-α in OS. Enforced expression of TGF-α sufficiently restore the effects of miR-205 on cell proliferation, invasion and migration. In conclusion, our study suggested that miR-205 may function as a tumor suppressor via targeting TGF-α in OS, and the abnormal expression of miR-205 might be a key factor in OS progression.