CircCPA4 Promotes the Malignant Phenotypes in Glioma via miR-760/MEF2D Axis

Circular RNA carboxypeptidase A4 (circCPA4) has been shown to involve in the tumorigenesis of glioma. However, the function and the molecular mechanism of circCPA4 in glioma remain inadequate. Levels of circCPA4 and microRNA (miR)-760 were detected by quantitative real-time polymerase chain reaction. Cell proliferation, apoptosis, migration, and invasion were analyzed using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), colony formation, flow cytometry, and transwell assays, respectively. Western blot was used to detect the protein levels of matrix metallopeptidase 2 (MMP2), MMP9 and myocyte enhancer factor 2D (MEF2D). The interaction between miR-760 and circCPA4 or MEF2D was analyzed by the dual-luciferase reporter assay or RNA pull-down assay. In vivo experiments were conducted using murine xenograft models. We found circCPA4 was highly expressed in glioma, and circCPA4 knockdown suppressed tumor cell proliferative, migratory and invasive behaviors, but enhanced cell apoptosis and radiosensitivity in glioma. CircCPA4 directly bound to miR-760 to suppress its expression, and miR-760 inhibition reversed circCPA4 knockdown-mediated inhibition of cell malignant phenotypes in glioma. MEF2D was a target of miR-760, and miR-760 performed anti-tumor effects by targeting MEF2D in glioma cells. Meanwhile, we found circCPA4 could indirectly regulate MEF2D by sponging miR-760. Importantly, xenograft analysis suggested that circCPA4 knockdown impeded tumor growth in vivo via regulating miR-760 and MEF2D. In conclusion, circCPA4 knockdown suppressed cell malignant phenotypes in glioma via miR-760/MEF2D axis to impede the progression of glioma, suggesting potential therapeutic targets for glioma treatment.