Circular RNA hsa_circ_0000517 modulates hepatocellular carcinoma advancement via the miR-326/SMAD6 axis

BACKGROUND: Hepatocellular carcinoma (HCC) is the most common malignant heterogeneous disease in primary liver tumors. Circular RNA hsa_circ_0000517 (hsa_circ_0000517) is connected with HCC prognosis. Nevertheless, there are few studies on the role and mechanism of hsa_circ_0000517 in HCC. METHODS: Expression of hsa_circ_0000517, miR-326, and SMAD family member 6 (SMAD6) was detected by quantitative real-time polymerase chain reaction (qRT-PCR). Cell viability, colony formation, cell cycle, migration, and invasion were determined though Cell Counting Kit-8 (CCK-8), colony formation, flow cytometry, wound healing, or transwell assays. Protein levels of Cyclin D1, matrix metalloproteinase-2 (MMP2), matrix metalloproteinase-9 (MMP9), SMAD6, and proliferating cell nuclear antigen (PCNA) were examined with western blot analysis. The relationship between hsa_circ_0000517 or SMAD6 and miR-326 was determined via dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. The role of hsa_circ_0000517 in vivo was confirmed via xenograft assay. RESULTS: Hsa_circ_0000517 and SMAD6 were up-regulated while miR-326 was down-regulated in HCC tissues and cells. Hsa_circ_0000517 down-regulation repressed cell proliferation, colony formation, migration, and invasion, and induced cell cycle arrest in HCC cells in vitro, and constrained tumor growth in vivo. Notably, hsa_circ_0000517 regulated SMAD6 expression via acting as a competing endogenous RNA (ceRNA) for miR-326. And the repressive influence on malignant behaviors of HCC cells mediated by hsa_circ_0000517 inhibition was reversed by miR-326 inhibitors. Moreover, SMAD6 elevation overturned the inhibitory impacts of miR-326 mimics on malignant behaviors of HCC cells. CONCLUSIONS: Hsa_circ_0000517 depletion repressed HCC advancement via regulating the miR-326/SMAD6 axis.