Circular RNA TTBK2 promotes the development of human glioma cells via miR-520b/EZH2 axis

D.-H. Yuan, J. Zhao, G.-F. Shao

Department of Neurosurgery, Zhuji People’s Hospital of Zhejiang Province, Zhuji, China. ningzhi2687526@163.com

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• Oncology

OBJECTIVE: Glioma is a highly malignant human disease characterized by limited response to clinical therapy. Evidence indicated that circular RNA Tau tubulin kinase 2 circular RNAs (circ-TTBK2) participated in glioma pathogenesis. However, the precise effect of circ-TTBK2 on glioma progression is needed to be highlighted.

MATERIALS AND METHODS: The levels of circ-TTBK2, microRNA-520b (miR-520b), and enhancer of zeste homologue 2 (EZH2) were detected via quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) or Western blot. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay was performed to determine cell proliferation in vitro. Besides, a flow cytometry assay was conducted to examine apoptosis of A172 and U251 cells. Cell invasion was identified using the transwell assay. Moreover, Dual-Luciferase reporter assay was used to confirm the interaction between miR-520b and circ-TTBK2 or EZH2. The role of circ-TTBK2 in glioma progression was exposed using xenograft tumor experiments.

RESULTS: The levels of circ-TTBK2 and EZH2 were markedly augmented, whereas miR-520b expression level was notably reduced in glioma tissues and cell lines. Either circ-TTBK2 or EZH2 detection could clearly facilitate cell apoptosis and block proliferation and invasion in A172 and U251 cells, while the effect of circ-TTBK2 or EZH2 deficiency was reverted by co-transfecting with miR-520 inhibitor. Moreover, circ-TTBK2 exerted its roles via miR-520b/EZH2 axis in glioma cells, and the knockdown of circ-TTBK2 could hinder the progression of glioma.

CONCLUSIONS: Circ-TTBK2/miR-520b/EZH2 axis modulated cell proliferation, apoptosis, and invasion in glioma cell lines, and might serve as potential targets for glioma diagnosis and therapy.

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