Circ_ANKIB1 stabilizes the regulation of miR-19b on SOCS3/STAT3 pathway to promote osteosarcoma cell growth and invasion.

Osteosarcoma is a highly malignant tumor. The molecular mechanism of its occurrence and development has not yet been clarified. Current studies have found that noncoding RNAs, such as circular RNAs (circRNAs) and microRNAs (miRNAs), play important regulatory roles in the progression of diseases. Our previous studies have shown that miR-19b is an oncogene in osteosarcoma. Further studies have shown that circ_ANKIB1 has binding sites for miR-19b, and both molecules were generally upregulated in osteosarcoma cells. RIP assay, RNA pull down, and dual-luciferase reporter gene assay showed that circ_ANKIB1 could directly bind to miR-19b and act as an miR-19b sponge in osteosarcoma cells. Circ_ANKIB1 promoted miR-19b expression, inhibited the expression of the downstream target gene SOCS3, and then activated the STAT3 pathway. When cotransfected with circ_ANKIB1 siRNA, and miR-19b mimics, the expression of SOCS3 and the phosphorylation level of STAT3 did not change significantly. Continuous detection of cell growth and invasion showed that the downregulation of circ_ANKIB1 or miR-19b significantly inhibited cell proliferation and invasion, but increased the apoptotic level. When cotransfected with circ_ANKIB1 siRNA and miR-19b mimics or SOCS3 siRNA, the cell proliferation, apoptosis, and invasion levels did not change significantly, suggesting that circ_ANKIB1 could affect the STAT3 pathway and osteosarcoma cell growth and invasion by enhancing the regulation of miR-19b on the downstream target gene SOCS3. These findings suggest that circRNAs stabilize miRNA functions, and further studies on this new function of circRNAs will provide a meaningful reference for the diagnosis and treatment of tumors and other diseases.