title: Genetic alteration and misexpression of Polycomb group genes in hepatocellular carcinoma.
abstract: Although the abnormal expression of Polycomb-group (PcG) proteins is closely associated with carcinogenesis and the clinicopathological features of hepatocellular carcinoma (HCC), the genetic mutation profile of PcG genes has not been well established. In this study of human HCC specimens, we firstly discovered a highly conserved mutation site, G553C, in the Polycomb Repressive Complex 2 (PRC2) gene enhancer of zeste homolog 2 (EZH2). This site also harbors a single nucleotide polymorphism (SNP), rs2302427, which plays an important antagonistic role in HCC. Kaplan-Meier survival curves showed that the tumor-free and overall survival of patients with EZH2 G553C were superior to those without the mutation. The G allele frequencies in patients and healthy subjects were 0.2% and 0.122%, respectively, with significant differences in distribution. The individuals carrying the GG and the GC genotypes at rs2302427 showed 3.083-fold and 1.827-fold higher risks of HCC, respectively, compared with individuals carrying the wild-type allele. Furthermore, Immunohistochemical staining revealed that the expression levels of CBX8 (in 53/123 samples) and BMI1 (in 60/130 samples) were markedly increased in human HCC specimens. Importantly, the overall and tumor-free survival rates were significantly reduced in the group of patients who simultaneously expressed PRC1 and PRC2. These results argue that a combination of PRC1 and PRC2 expression has a significant predictive/prognostic value for HCC patients. Taken together, our results indicate the abnormal expression and genetic mutation of PcG members are two independent events; cumulative genetic and epigenetic alterations act synergistically in liver carcinogenesis.
authors.affiliation: Department of Basic Medical Sciences, Medical College Xiamen 361102, P.R. China ; Fujian Provincial Key Laboratory of Chronic Liver Disease and Hepatocellular Carcinoma, Xiamen University Chengzhi Building 110, Xiang'an South Road, Xiamen 361102, P.R. China.
authors.forename: Shu-Bin
authors.initials: SB
authors.lastname: Gao
authors.affiliation: Ministry of Health Key Laboratory of Radiobiology, Jilin University 1163 Xinmin Road, Changchun 130021, P.R. China.
authors.forename: Shi-Long
authors.initials: SL
authors.lastname: Sun
authors.affiliation: Department of Basic Medical Sciences, Medical College Xiamen 361102, P.R. China.
authors.forename: Qi-Lin
authors.initials: QL
authors.lastname: Zheng
authors.affiliation: Department of Basic Medical Sciences, Medical College Xiamen 361102, P.R. China ; Fujian Provincial Key Laboratory of Chronic Liver Disease and Hepatocellular Carcinoma, Xiamen University Chengzhi Building 110, Xiang'an South Road, Xiamen 361102, P.R. China.
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Medical Research Center, Department of Radiation Oncology, Peking University Third Hospital Beijing 100191, P.R. China.
authors.forename: Yuequan
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Department of Basic Medical Sciences, Medical College Xiamen 361102, P.R. China ; Fujian Provincial Key Laboratory of Chronic Liver Disease and Hepatocellular Carcinoma, Xiamen University Chengzhi Building 110, Xiang'an South Road, Xiamen 361102, P.R. China.
authors.forename: Guang-Hui
authors.initials: GH
authors.lastname: Jin
authors.affiliation: Medical Research Center, Department of Radiation Oncology, Peking University Third Hospital Beijing 100191, P.R. China.
authors.forename: Li-Xiang
authors.initials: LX
authors.lastname: Xue
keywords: H3K27 trimetylation; Hepatocellular carcinoma; Polycomb; SNP