EZH2-mediated H3K27me3 enrichment on the lncRNA MEG3 promoter regulates the growth and metastasis of glioma cells by regulating miR-21-3p.

Objective: Glioma is one of the most common and invasive brain tumors worldwide. Long non-coding RNAs (LncRNAs) play an important role in the development of glioma. However, the regulatory mechanism of LncRNAs in glioma has not been fully elucidated. This study aimed to explore the interaction of lncRNA maternally expressed gene 3 (MEG3) and aberrant histone modification in glioma.
Materials and Methods: The expression levels of MEG3 and miR-21-3p in glioma cells were measured by quantitative polymerase chain reaction (qPCR). EZH2 (enhancer of zeste homolog 2) and H3K27me3 expression in glioma cells were detected by Western Blot (WB). The binding site of the promoter of MEG3 by H3K27me3 was confirmed by ChIP-Real-time PCR. The direct target of MEG3 and miR-21-3p in glioma cells was measured by a luciferase reporter assay. Cell proliferation was detected by Cell Counting Kit-8 (CCK8), and cell invasion and migration were measured by Transwell assays.
Results: EZH2 and miR-21-3p were upregulated and MEG3 was downregulated in glioma cells. Silencing of EZH2 inhibited cell proliferation, migration, and invasion in U87 and U251 cells. Meanwhile, the expression of H3K27me3 could be significantly inhibited by EZH2 interference. H3K27me3 protein can bind to MEG3 promoter directly. EZH2 inhibition and MEG3 down-expression in U87 cells reversed the effects of silencing of EZH2 on glioma cell growth and metastasis. However, EZH2 inhibition and MEG3 overexpression in U251 cells restricted cell proliferation, migration, and invasion. Furthermore, miR-21-3p was verified to interact with MEG3 by direct binding. Inhibition of MEG3 promoted U87 cell growth and metastasis, which was further strengthened following the co-transfection of si-MEG3 and miR-21-3p. Overexpressed MEG3 inhibited U251 cell growth and metastasis and a complete reversal of the results observed in the co-transfection of LV-MEG3 and miR-21-3p.
Conclusions: EZH2 was highly expressed in glioma cells and EZH2-mediated H3K27me3 enrichment on the MEG3 promoter regulated the growth and metastasis of glioma cells by targeting miR-21-3p. It potentially provided a new therapeutic marker targeting glioma.