Feedback Loop of EZH2/miR-101 Regulates Autophagy and Apoptosis by Targeting mTOR in Glioblastoma Cells

Abstract

Background: Enhancer of zeste homolog 2 (EZH2) acts as an essential epigenetic modifier that has been reported to be changed in glioblastoma (GBM). This study aims to explore the molecular mechanism of EZH2 in GBM. Methods: In this current study, we first analyzed the expression of EZH2 in glioma and GBM cell lines by The Cancer Genome Atlas (TCGA), Chinese Glioma Genome Atlas (CGGA), Rembrandt databases, and western blotting. Then, we constructed EZH2-silencing lentiviral vectors (LV-EZH2-siRNA) to transfect glioma cells and to establish a subcutaneous tumor model. Different concentrations of EZH2 inhibitors (GSK126) and autophagy inhibitor (autophinib) were selected to investigate their effects on GBM cell apoptosis. We examined the relationship between mammalian target of rapamycin (mTOR) or EZH2 and microRNA (miR)-101 to explore potential molecular mechanisms. An intracranial homograft model was established to investigate the therapeutic effect of GSK126 on GBM. Results: EZH2 knockdown and GSK126 could diminish the invasion, migration, and proliferation of GBM cells. The autophagy level and apoptosis rate were elevated in GBM cells treated with the GSK126 (p < 0.05). Additionally, GSK126 modulated the expression of miR-101 via Trimethylation of histone H3 lysine 27 (H3K27me3) modification in the miR-101 promoter region and regulated the protein expression of mTOR, a target of miR-101. GSK126 could inhibit the growth of GBM in vivo. Conclusions: EZH2 affects the autophagy and apoptosis of GBM cells via mTOR signaling through the feedback loop of EZH2/miR-101, hence providing a promising target for developing new therapeutic intervention strategies for GBM.