Circ_0051079 silencing inhibits the malignant phenotypes of osteosarcoma cells by the TRIM66/Wnt/β-catenin pathway in a miR-625-5p-dependent manner

BACKGROUND: Circular RNA (circRNA) is a newly-discovered endogenous transcript that has been reported to participate in osteosarcoma (OS) progression. However, the underlying mechanism of circ_0051079 modulating OS development remains unclear. METHODS: RNA expressions of circ_0051079, miR-625-5p and tripartite motif containing 66 (TRIM66) were detected by quantitative real-time polymerase chain reaction. Protein expression was checked by Western blot analysis. The functional effects of circ_0051079 on OS cell malignancy were investigated by cell counting kit-8, clonogenicity, transwell, tube formation and flow cytometry assays. The interactions among circ_0051079, miR-625-5p and TRIM66 were identified by dual-luciferase reporter and RNA immunoprecipitation assays. Mouse xenograft model assay was performed to elucidate the effects of circ_0051079 knockdown on tumor formation in vivo. RESULTS: Circ_0051079 and TRIM66 expressions were significantly upregulated, but miR-625-5p was downregulated in OS tissues and cells compared with control groups. Circ_0051079 expression was significantly associated with tumor-node-metastasis stage and tumor size of OS patients. Circ_0051079 knockdown inhibited OS cell proliferation, migration and invasion, repressed angiogenesis but induced cell apoptosis, accompanied by the decreases of PCNA and Bcl-2 production and an increase of Bax production. MiR-625-5p, a target miRNA of circ_0051079, participated in regulating circ_0051079-induced effects. Also, TRIM66 was identified as a target mRNA of miR-625-5p, and partially attenuated the inhibitory effects of miR-625-5p in OS cells. Circ_0051079 modulated the Wnt/β-catenin pathway through TRIM66 in vitro. Importantly, circ_0051079 silencing reduced TRIM66 expression by interacting with miR-625-5p. Further, circ_0051079 depletion inhibited tumor formation in vivo. CONCLUSION: Circ_0051079 regulated OS development by the miR-625-5p/TRIM66/Wnt/β-catenin pathway, providing a novel therapeutic target for OS.