Retracted Article: Overexpression of circ_0034642 contributes to hypoxia-induced glycolysis, cell proliferation, migration and invasion in gliomas by facilitating TAGLN2 expression via sponging miR-625-5p

Glioma is an aggressive brain cancer with poor prognosis and high invasiveness. Dysregulation of circular RNAs (circRNAs) has been widely discovered in various cancers, including glioma. However, the molecular mechanism of circ_0034642 in glioma is still unclear. The expression of circ_0034642, microRNA (miR)-625-5p and transgelin-2 (TAGLN2) in glioma tumors and cells was detected by performing a quantitative real-time polymerase chain reaction (qRT-PCR). The stability of circ_0034642 was determined by carrying out RNase R treatment. Cell proliferation was evaluated by performing the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Glycolysis was analyzed by measuring the extracellular acidification rate (ECAR) using glucose detection and lactic acid detection kits. Cell migration and invasion were determined by performing the transwell assay. Protein expression levels of the proteins hexokinase 2 (HK2), matrix metalloproteinase-2 (MMP2), matrix metalloproteinase-9 (MMP9) and TAGLN2 were analyzed using western blots. The interaction between miR-625-5p and circ_0034642 or TAGLN2 was proved using a dual-luciferase reporter system. Animal models were established by subcutaneously injecting glioma cells stably transfected with sh-NC or sh-circ_0034642. Circ_0034642 and TAGLN2 were overexpressed whereas miR-625-5p was expressed at low levels in glioma tumors and cells. Moreover, circ_0034642 and TAGLN2 were upregulated while miR-625-5p was downregulated under hypoxic conditions in a time-dependent manner. Next, elimination of circ_0034642 was shown to inhibit cell glycolysis, proliferation, migration and invasion under hypoxic conditions in gliomas. Then, we found that circ_0034642 acted as a “sponge” of miR-625-5p while TAGLN2 acted as a target of miR-625-5p. In addition, recovery of circ_0034642 attenuated the repression mediated by miR-625-5p on glioma cell glycolysis and progression under hypoxic conditions. Meanwhile, an inhibitor of miR-625-5p alleviated TAGLN2 deficiency-induced inhibition of glioma cell development under hypoxic conditions. We also discovered that circ_0034642 could interact with miR-625-5p and further alter the expression of TAGLN2. Lastly, a circ_0034642 knockdown hindered tumor growth in vivo by regulating the miR-625-5p/TAGLN2 axis. Enhanced expression of circ_0034642 was found to promote cell glycolysis, proliferation, migration and invasion under hypoxic conditions in gliomas by sponging miR-625-5p to improve TAGLN2 expression, providing prospective biomarkers for the diagnosis of glioma.