Decreased expression of H3K27me3 in human ovarian carcinomas correlates with more aggressive tumor behavior and poor patient survival

It has been confirmed that trimethylation of lysine 27 on histone H3 (H3K27me3) plays an important role in epigenetic process of tumorigenesis. However, the status of H3K27me3 in ovarian cancer and its impact on patients' clinicopathologic characteristics and prognosis are unclear. In the present study, the immunohistochemistry (IHC) was utilized to detect protein expression of H3K27me3 in 12 normal ovaries, 26 ovarian cystadenomas, 31 borderline ovarian tumors and 168 ovarian carcinomas by tissue microarray. The association between H3K27me3 expression with clinicopathologic features and patient prognosis were also evaluated using various statistical models. The expression of H3K27me3 was decreased in 2 of 12 (16.7%) cases of the normal ovaries, 8 of 26 (30.8%) cases of cystadenomas, 12 of 31 (38.7%) cases of borderline ovarian tumors, and 93 of 168 (55.4%) cases of primary ovarian carcinomas, respectively (P<0.05). Further correlation analysis suggested that decreased expression of H3K27me3 in ovarian carcinomas was significantly correlated with more advanced pM and FIGO stages (P<0.05). In addition, a significant association between decreased expression of H3K27me3 and shortened patient survival (mean 66 months versus 101 months, p=0.019) was demonstrated by univariate survival analysis of the ovarian carcinoma cohorts. Importantly, H3K27me3 expression provided a significant independent prognostic factor in multivariate analysis (p=0.028). These findings confirmed that decreased expression of H3K27me3 in primary ovarian cancer might be correlated with the acquisition of an invasive and/or aggressive phenotype of tumor, and might serve as an independent biomarker for poor prognosis in patients with ovarian carcinoma.