EZH2 expression in hepatocellular carcinoma and its relationship with circadian rhythm-related genes

Hepatocellular carcinoma (HCC) is the most prevalent liver malignancy, with increasing incidence and high mortality, primarily associated with hepatitis virus infection and cirrhosis. Herein, we explored the association between enhancer of zeste homolog 2 (EZH2) expression and HCC progression, prognosis, and circadian rhythm-related genes. Differentially expressed mRNAs in HCC were identified from The Cancer Genome Atlas and Gene Expression Omnibus databases and intersected with circadian rhythm-related genes. Core genes were screened using protein-protein interaction networks, least absolute shrinkage and selection operator regression, and Cox regression analysis. Functional enrichment and immune infiltration analyses were conducted using gene set variation analysis, single-sample gene set enrichment analysis, and MethSurv. Experimental validation included western blotting, small interfering RNA knockdown, reverse transcription quantitative polymerase chain reaction, and functional assays. EZH2 was overexpressed in HCC and was associated with advanced tumor stage, poor prognosis, Th2 and dendritic cell infiltration, and promoter hypermethylation. EZH2 knockdown inhibited proliferation, induced DNA damage, and downregulated CLOCK and CRY1 expression. A prognostic nomogram integrating EZH2 expression with clinicopathological parameters demonstrated strong predictive performance. Methylation analysis identified six CpG sites significantly associated with survival. In conclusion, EZH2 is a key regulator of HCC progression and potential prognostic biomarker and therapeutic target.