CircECE1 promotes osteosarcoma progression through regulating RAB3D by sponging miR-588

BACKGROUND: Circular RNAs (circRNAs) have been confirmed to be involved in cancer pathogenesis. However, the underlying mechanism of circRNA endothelin converting enzyme 1 (circECE1) in osteosarcoma (OS) development is still not understood. METHODS: The expression levels of circECE1, microRNA-588 (miR-588) and RAB3D, member RAS oncogene family (RAB3D) were gauged by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot. OS cell proliferation was assessed by cell counting kit-8 (CCK-8) assay and 5-ethynyl-2’-deoxyuridine (EdU) assay. OS cell apoptosis rate and metastasis were identified by flow cytometry and transwell assay. Dual-luciferase reporter analysis and RNA immunoprecipitation (RIP) assay were performed to confirm the interactions among circECE1, miR-588 and RAB3D. Xenograft tumor models were established to explore circECE1 function in vivo. Immunohistochemistry (IHC) assay was applied to analyze RAB3D level after circECE1 knockdown. RESULTS: In OS, circECE1 expression was higher than that in normal chondroma tissues. High levels of circECE1 were positively linked to OS cell viability, proliferation, migration and invasion, and negatively linked to OS cell apoptosis rate. It was found that circECE1 was a miR-588 sponge, and miR-588 inhibitor abrogated the influence of si-circECE1 on OS cells. MiR-588 targeted RAB3D to further regulate the pathological process of OS. Moreover, silencing circECE1 blocked OS tumor growth in vivo. CONCLUSION: We elucidated the function of a novel circECE1/miR-588/RAB3D axis in OS progression.