The expression and significance of histone lysine methylation in endometrial cancer.

Histone modifications of lysine residues have been implicated as having diagnostic and/or prognostic significance in numerous types of cancer. In the present study, the significance of the histone H3 methylation of lysine 4 (H3K4) and lysine 27 (H3K27) were investigated in endometrial cancer. Specifically, immunohistochemical analysis was used to detect the cellular expression levels of H3K27 trimethylation (H3K27me3), H3K4 trimethylation (H3K4me3) and H3K4 dimethylation (H3K4me2) in glandular epithelial tissues and stromal tissues. The association between the methylation levels of histone markers and clinicopathological parameters were analyzed. The results demonstrated that in epithelial cells, H3K4me2 and H3K4me3 exhibited the highest levels in endometrial cancer, followed by precancerous lesions and a normal endometrium. Low expression levels of H3K4me2 in glandular epithelium of endometrial cancer were significantly associated with a clinical early International Federation of Gynecology and Obstetrics stage (P=0.006). For stromal tissues, the expression level of H3K27me3 in Type 1 endometrial cancer was significantly lower compared with that in the normal endometrium (P=0.043) and precancerous lesions (P<0.001). The expression level of H3K4me2 was significantly lower in the stroma of Type 1 and 2 cancer compared within the normal endometrium (P=0.005). A low H3K4me3 expression level in the stroma of endometrial cancer tissues was associated with P53-negativity (P=0.032). In conclusion, the cellular expression levels of histone H3 methylation were differentially presented in glandular epithelial and stromal elements in endometrial tissues. A low expression level of activation marker H3K4me2 in glandular epithelium defined a subset of patients with early-stage endometrial adenocarcinoma and may have potential prognostic value.