c-MYC Regulates EZH2/miR-200b-3p/DNMT3A Pathway to Promote Proliferation and Invasion in Hepatocellular Carcinoma

Abstract

Background: This study explored the mechanism underlying the regulation of the EZH2/miR-200b-3p/DNMT3A (enhancer of zeste homolog 2/micro ribonucleic acid-200b-3p/deoxyribonucleic acid methyltransferase 3 alpha) pathway by c-MYC in hepatocellular carcinoma (HCC). Methods: The mRNA (messenger ribonucleic acid) and protein expression of c-MYC, EZH2, and DNMT3A in HCC cell lines were examined using quantitative reverse transcription-quantitative polymerase chain reaction and Western blotting, respectively. The knockdowns of c-MYC, EZH2, or DNMT3A and DNMT3A overexpression were achieved through the transfection of corresponding small interfering RNAs and overexpression vectors, respectively. miR-200b-3p mimics or inhibitors were transfected into HCC cells for miR-200b-3p overexpression or knockdown. Colony formation and cell counting kit-8 assays were performed to measure cell proliferation viability, respectively. The apoptosis and invasion were examined using flow cytometry and Transwell invasion assay, respectively. Results: c-MYC silencing significantly upregulated miR-200b-3p expression, and EZH2 knockdown enhanced miR-200b-3p levels in HepG2 and SMMC-7721 cells. miR-200b-3p targeted DNMT3A and reduced DNMT3A mRNA level, whereas DNMT3A reduced miR-200b-3p levels through the promotion of miR-200b-3p promoter methylation. In HepG2 and SMMC-7721 cells, miR-200b-3p overexpression promoted apoptosis and inhibited invasion and proliferation. Conclusions: c-MYC regulates the EZH2/miR-200b-3p/DNMT3A pathway and affects the invasion and proliferation of HCC cells. miR-200b-3p and DNMT3A form a feedback loop to enhance miR-200b-3p inhibition and DNMT3A overexpression.