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

Abstract

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.

Competing Endogenous RNA Networks in Glioma

“…MiR-760 is a well-identified tumor-suppressive miRNA that functions in many types of cancers, including hepatocellular carcinoma ( Tian et al, 2018 ), breast cancer ( Han et al, 2016 ), and non-small cell lung cancer ( Zhu et al, 2019 ), via regulating the malignant properties of tumor, such as cell proliferation, apoptosis, migration, and drug resistance. Then, Zhang Y. et al (2020) confirmed that MEF2D is targeted by miR-760 glioma cells. MEF2D is a transcription factor of the myocyte-specific enhancer factor 2 (MEF2) family involved in the regulation of the differentiation and development of muscle and neuronal cells ( McKinsey et al, 2002 ).…”

“… Zhang Y. et al (2020) further explored the circCPA4 function in glioma cells and found that suppression of the circRNA inhibits tumor cell proliferation, migration, and invasion while promoting cell apoptosis and radiosensitivity in vitro and repressing tumor growth in vivo . They pointed out that a higher expression of circCPA4 is positively correlated with tumor size, WHO grade, and poor prognosis in patients.…”

“…They pointed out that a higher expression of circCPA4 is positively correlated with tumor size, WHO grade, and poor prognosis in patients. Differently from Peng et al (2019) in the mechanism, Zhang Y. et al (2020) revealed that circCPA4 sponges MEF2D (myocyte enhancer factor 2D)-targeting miR-760 to promote glioma progress. Knockdown of miR-760 can reverse the antitumor effects mediated by the suppression of circCPA4.…”

CircCPA4 induces ASCT2 expression to promote tumor property of non‐small cell lung cancer cells in a miR‐145‐5p‐dependent manner

“…An early study has indicated that circCPA4 contributes to the aggressive progression of glioma. 26 Additionally, our F I G U R E 7 CircCPA4/miR-145-5p/ASCT2 axis regulated intracellular glutamine, glutamate and α-KG levels. (a-c) Si-NC, si-circCPA4, si-circCPA4 + inhibitor NC, and si-circCPA4 + miR-145-5p inhibitor were transfected into A549 and H1299 cells, and the corresponding kits were used to evaluate intracellular glutamine, glutamate and α-KG levels.…”

Research Progress on Circular RNA in Glioma

“…Radiation-induced damage to the glioma microenvironment may generate a tumor-susceptible niche and facilitate invasion and migration of residual glioma cells, contributing to disease relapse. CircATP8B4 and circCPA4 are overexpressed in glioma and reduce radiation sensitivity of glioma cells by serving as sponges for miR-766 and miR-760, respectively ( 38 , 120 ). Studies have also shown that circ_VCAN expressed at a higher level in radioresistant gliomas cells compared to sensitive cells and overexpression of circ_VCAN accelerate carcinogenesis and reduce the radiosensitivity of gliomas by regulating miR-1183 ( 39 ).…”