Regulation of osteosarcoma cell invasion through osteopontin modification by miR-4262

Osteopontin (OPN) is a phosphorylated glycoprotein that plays a critical role in the invasion of osteosarcoma (OS), the most common primary malignant bone tumor. Since microRNAs (miRNAs) have been well documented as key players in the tumorigenesis, cancer cell growth, and metastases, determination of the involved miRNAs that may regulate OPN-mediated OS cell invasion appears to be one important question in the current understanding and therapeutic strategies for OS. Here, we found that the levels of miR-4262 were significantly decreased and the levels of OPN were significantly increased in OS specimens, compared to the paired adjacent non-tumor tissue. Moreover, miR-4262 and OPN inversely correlated in OS specimens. The 5-year survival of the patients with lower miR-4262 levels in the resected OS was worse than that of patients with high miR-4262 levels. Bioinformatics analyses showed that miR-4262 targeted the 3'-UTR of OPN mRNA to inhibit its translation, which was proved by luciferase reporter assay. Furthermore, miR-4262 overexpression inhibited OPN-mediated cell invasion, while miR-4262 depletion increased OPN-mediated cell invasion in OS cells, in both a transwell cell invasion assay and a scratch wound healing assay. Together, our data suggest that suppression of miR-4262 in OS cells may promote OPN-mediated cancer invasion, highlighting miR-4262 as an intriguing therapeutic target to prevent OS metastases.