EZH2-mediated hypermethylation of H3K27me3 downregulates claudin-4 and upregulates the Wnt/β-catenin signaling pathway in hepatocellular carcinoma metastasis

Enhancer of zeste homolog 2 (EZH2) is often overexpressed in malignant tumors and plays a key role in metastasis by trimethylating lysine 27 on histone H3 (H3K27me3). However, the exact mechanism by which EZH2 facilitates metastasis in the diethylnitrosamine (DEN) and N-nitrosomorpholine (NMOR)-induced hepatocellular carcinoma (HCC) model remains unexplored. In this study, we demonstrated that EZH2 expression is elevated in HCC and is associated with metastasis to lung tissue, with poor overall survival outcomes. EZH2 overexpression in HCC liver tissues inhibited claudin-4 gene expression and promoted the activation of the Wnt/β-catenin signaling pathway. β-catenin signaling activates Lymphoid Enhancer-Binding Factor 1(LEF-1) transcription factors that regulate the expression of genes involved in epithelia-to-mesenchymal transition (EMT) and metastasis. EZH2 overexpression significantly elevates H3K27me3 at the promoter, suppressing claudin-4 expression. This leads to increased levels of Matrix metalloproteinase-9 (MMP-9) and vimentin, enhancing the invasion, migration, and metastasis of hepatocellular carcinoma (HCC) cells. However, inhibiting EZH2 with tazemetostat subsequently enhanced claudin-4 expression by reducing Wnt/β-catenin signaling activity and inhibiting EMT-inducing factors.