High expression of EZH2 is associated with the tumor grade in human hepatocellular carcinomas

Abstract

Background It was documented that trimethylation of lysine 27 on histone H3 (H3K27me3) has contradictory prognostic impacts in different human cancers. H3K27me3 is known to be induced by enhancer of zeste homolog 2 (EZH2). Recently, only few reports have documented that overexpression of H3K27me3 and EZH2 were positively associated with aggressiveness and poor prognosis in hepatocellular carcinoma (HCC) patients. Methods Immunohistochemical analysis (IHC) was used to examine protein expression of H3K27me3 and EZH2 in 67 HCC tissues. Nuclear immunoreactivity for H3K27me3 and EZH2 proteins was scored in a semiquantitative method by evaluation of the number of positive tumor cells over the total number of tumor cells. The results obtained were correlated with various clinicopathological parameters. Results The expression of EZH2 was significantly and positively correlated with the tumor grade (p = 0.014), but not with other clinicopathological parameters. No significant correlation of H3K27me3 was found. Multivariate Cox regression analysis showed that no significant correlation of EZH2 or H3K27me3 was found. A significant positive correlation between expression of H3K27me3 and EZH2 was observed (p = 0.001). Discussion These findings provide evidence that a high expression of EZH2 correlates closely with the tumor grade of HCCs but fails to be of prognostic value in multivariate analysis.