Abstract
Ras-related protein Rab-31 (RAB31), a small guanosine 5'-triphosphate-binding protein, is a member of the Rab family and has been demonstrated to serve an oncogenic role in several common types of human cancer. However, the function of RAB31 in osteosarcoma (OS) has not been previously studied. The present study identified that the expression levels of RAB31 were significantly higher in OS tissue samples compared with matched adjacent non-tumor tissue samples, and high RAB31 expression was associated with malignant progression and a poor prognosis for patients with OS. Furthermore, it was identified that the expression levels of RAB31 were increased in OS cell lines compared with normal osteoblast cells. Silencing of RAB31 expression significantly inhibited OS cell proliferation, cell cycle progression, migration and invasion, and significantly increased the rate of cell apoptosis. In addition, the present study used a luciferase reporter assay to demonstrate that RAB31 was a direct target gene of microRNA-26b (miR-26b), which is a known tumor suppressor in OS. The expression levels of RAB31 were negatively associated with miR-26b expression in OS cells. Finally, miR-26b was demonstrated to be significantly decreased in OS tissues compared with adjacent non-tumor tissues, and an inverse correlation was observed between the expression levels of RAB31 and miR-26b in OS tissues. In summary, to the best of our knowledge, the present study is the first to report that RAB31 is a target gene of miR-26b, and silencing of RAB31 may inhibit OS growth and progression.