Mechanism of the Regulatory Effect of Overexpression of circMTO1 on Proliferation and Apoptosis of Hepatoma Cells via miR-9-5p/NOX4 Axis

Purpose: To investigate the potential role of the circMTO1/miR-9-5p/NOX4 axis in liver cancer. Materials and Methods: Human genome-wide circrna microarray V2 was used for analyzing the expression profile of circRNAs in human tissue samples. The TargetScan database was used to predict target genes. Gene overexpression and silencing in hepatoma cell lines were achieved by transfecting the cells with suitable constructs. Quantitative real time PCR and Western blotting were used to analyze gene and protein expression levels. CCK-8 analysis was performed to detect cell proliferation and the transwell assay for analyzing cell migration. Annexin V-FITC/PI staining and immunohistochemistry were respectively used to detect apoptosis and protein expression. Results: CircMTO1 were down-regulated in the liver cancer tissues and cell lines compared to their respective normal controls. TargetScan database screening and dual luciferase assay revealed that circMTO1 was a molecular sponge of miR-9-5p, and NOX4 was the target gene of miR-9-5p. Overexpression of circMTO1 and NOX4 inhibited proliferation and migration of hepatoma cells, while the overexpression of miR-9-5p had the opposite effects. In contrast, overexpression of circMTO1 and NOX4 promoted apoptosis, while that of miR9-5p decreased the cell apoptosis rates. Conclusion: Overexpression of CircMTO1 acts as tumor suppressor in liver cancer by sponging miR-9-5p, which upregulates NOX4.