The global histone modification pattern correlates with overall survival in metachronous liver metastasis of colorectal cancer.

Post-translational histone modifications are known to be altered in cancer tissues, and differences in the histone modification levels have recently been used to predict the clinical outcome in patients with certain types of cancer. In this study, we evaluated the immunohistochemical staining patterns of histone H3 dimethylation and acetylation in metachronous liver metastasis of colorectal carcinomas and examined its correlation with patient prognosis. Double 2 mm core tissue microarrays were made from 54 paraffin-embedded samples of liver metastasis from colorectal adenocarcinoma, and were examined by an immunohistochemical analysis of histone H3 lysine 4 (H3K4) dimethylation, histone, H3 lysine 9 (H3K9) dimethylation and histone H3 lysine 9 (H3K9) acetylation. Positive tumor cell staining for each histone modification was used to classify patients into low- and high-staining groups, which were then examined for correlations with the clinicopathological parameters and clinical outcome. Dimethylation of H3K4 correlated with the tumor histological type (P=0.043), and acetylation of H3K9 correlated with the tumor histological type (P=0.016). In addition, lower levels of H3K4 dimethylation correlated with a poor survival rate (P=0.035). The multivariate survival analysis showed that the H3K4 dimethylation status is an independent prognostic factor for colorectal cancer patients (P=0.011). We suggest that the pattern of histone modification as detected by immunohistochemistry may be an independent prognostic factor for metachronous liver metastasis of colorectal carcinomas.