Abstract:Objective To investigate the effects of circular RNA 0000064 (circ_0000064) targeting miR-503 on the biological behavior of thyroid cancer cells.Methods The expression levels of circ_0000064 and miR-503 in the thyroid cancer tissues and the corresponding adjacent tissues of 21 cases were assessed using real-time quantitative PCR (RT-qPCR). Circ_0000064 small interfering RNA (si-circ_0000064), miR-503 mimic, si-circ_0000064 + miR-503 inhibitor (anti-miR-503) were transfected into thyroid cancer SW579 cells, respectively. The plate cloning formation test and cell counting kit (CCK-8) method were applied to calculate the proliferation of SW579 cells, and Transwell test was performed to detect the migration and invasion of SW579 cells. Flow cytometry was selected to detect the cell apoptosis, and Western blotting was employed to detect the expressions of epithelial cadherin (E-cadherin) and neural cadherin (N-cadherin) proteins. The targeted regulation relationship between circ_0000064 and miR-503 was confirmed by dual luciferase reporter assay and RT-qPCR.Results The expression of circ_0000064 was significantly higher in thyroid cancer tissues than in adjacent tissues (P<0.05), while the expression of miR-503 was significantly lower in thyroid cancer tissues than in adjacent tissues (P<0.05). The cell viability, colony formation numbers, migration and invasion numbers, and N-cadherin protein expression of SW579 cells were significantly decreased (P<0.05), while E-cadherin protein expression was significantly increased (P<0.05) after silencing circ_0000064. The cell viability, colony formation numbers, migration and invasion numbers, N-cadherin protein expression of SW579 cells were significantly decreased (P<0.05), while E-cadherin protein expression was significantly increased (P<0.05) after overexpressing miR-503. miR-503 was the target gene of circ_0000064, and silencing circ_0000064 significantly increased the expression of miR-503 (P<0.05). miR-503 inhibition significantly weakened the effects of silencing circ_0000064 on the biological behavior of SW579 cells (P<0.05).Conclusion Silencing circ_0000064 can inhibit the proliferation, migration and invasion, and induce the apoptosis of thyroid cancer cells by up-regulating the expression of miR-503, thereby inhibiting the progression of thyroid cancer.