Circ_0000745 strengthens the expression of CCND1 by functioning as miR-488 sponge and interacting with HuR binding protein to facilitate the development of oral squamous cell carcinoma.

BACKGROUND: The implication of circular RNAs (circRNAs) in human cancers has aroused much concern. In this study, we investigated the function of circ_0000745 and its potential functional mechanisms in oral squamous cell carcinoma (OSCC) to further understand OSCC pathogenesis. METHODS: The expression of circ_0000745, miR-488 and cyclin D1 (CCND1) mRNA was measured by quantitative real-time polymerase chain reaction (qPCR). Cell proliferation capacity was assessed by cell counting kit-8 (CCK-8) assay and colony formation assay. Cell cycle progression and cell apoptosis were determined by flow cytometry assay. The protein levels of CCND1, PCNA, Cleaved-caspase 3 and HuR were detected by western blot. Animal study was conducted to identify the role of circ_0000745 in vivo. The targeted relationship was verified by dual-luciferase reporter assay, pull-down assay or RNA immunoprecipitation (RIP) assay. RESULTS: The expression of circ_0000745 was increased in OSCC tissues and cells. Circ_0000745 downregulation inhibited OSCC cell proliferation and induced cell cycle arrest and apoptosis in vitro, as well as blocked tumor growth in vivo. MiR-488 was a target of circ_0000745, and circ_0000745 downregulation suppressed OSCC development by enriching miR-488. Besides, circ_0000745 regulated CCND1 expression by targeting miR-488. In addition, circ_0000745 regulated CCND1 expression by interacting with HuR protein. CCND1 knockdown also inhibited OSCC cell proliferation and induced cell cycle arrest and apoptosis in vitro, and CCND1 overexpression recovered the inhibitory effects on OSCC cell malignant behaviors caused by circ_0000745 downregulation. CONCLUSIONS: Circ_0000745 regulated the expression of CCND1 partly by acting as miR-488 sponge and interacting with HuR protein, thus promoting the progression of OSCC.