Deregulation of RB1 expression by loss of imprinting in human hepatocellular carcinoma
Deregulation of RB1 expression by loss of imprinting in human hepatocellular carcinoma
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DOI：
10.1002/path.4376
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发表时间：
2014-08-01
影响因子：
7.3
通讯作者：
Lehmann, Ulrich
中科院分区：
文献类型：
--
作者：
Anwar, Sumadi Lukman;Krech, Till;Lehmann, Ulrich
肿瘤抑制基因RB1在许多不同类型的人类癌症中经常沉默，包括肝细胞癌（HCC）。然而，RB1基因的突变在HCC中相对罕见。对人类HCC中不受调控的印迹基因的系统筛选显示，RB1在大部分原发性患者样本中显示出印记异常。总的来说，40%的HCC标本（16/40）显示RB1基因内含子2的CpG岛高甲基化或低甲基化。对公开的全基因组DNA甲基化数据的重新分析在两个独立的HCC队列中证实了这些发现。通过实时荧光定量PCR检测，RB1位点正确DNA甲基化模式的缺失会导致RB1- e2b转录物的异常表达。通过DNMT1敲除或DAC处理，内含子2 CpG岛的去甲基化刺激RB1- e2b转录物的表达，同时RB1主要转录物的表达减少。在肝细胞腺瘤（HCA, n = 10）、局灶性结节性增生（FNH, n = 5）及其相应的邻近肝组织标本中，RB1位点未发现异常DNA甲基化。由于RB1基因内含子2的高甲基化或低甲基化而导致的RB1表达失调在肿瘤中被发现，而没有杂合性的丧失，如果是由CpG85的高甲基化引起的，则与总生存率的降低相关（p = 0.032）。这明确表明，印迹的缺失是人类HCC中RB1通路失活的一个重要的附加机制，补充了已经描述好的分子缺陷。版权所有2014年英国和爱尔兰病理学会。约翰·威利父子有限公司出版。
The tumour suppressor gene RB1 is frequently silenced in many different types of human cancer, including hepatocellular carcinoma (HCC). However, mutations of the RB1 gene are relatively rare in HCC. A systematic screen for the identification of imprinted genes deregulated in human HCC revealed that RB1 shows imprint abnormalities in a high proportion of primary patient samples. Altogether, 40% of the HCC specimens (16/40) showed hyper- or hypomethylation at the CpG island in intron 2 of the RB1 gene. Re-analysis of publicly available genome-wide DNA methylation data confirmed these findings in two independent HCC cohorts. Loss of correct DNA methylation patterns at the RB1 locus leads to the aberrant expression of an alternative RB1-E2B transcript, as measured by quantitative real-time PCR. Demethylation at the intron 2 CpG island by DNMT1 knock-down or aza-deoxycytidine (DAC) treatment stimulated expression of the RB1-E2B transcript, accompanied by diminished RB1 main transcript expression. No aberrant DNA methylation was found at the RB1 locus in hepatocellular adenoma (HCA, n = 10), focal nodular hyperplasia (FNH, n = 5) and their corresponding adjacent liver tissue specimens. Deregulated RB1 expression due to hyper- or hypomethylation in intron 2 of the RB1 gene is found in tumours without loss of heterozygosity and is associated with a decrease in overall survival (p = 0.032) if caused by hypermethylation of CpG85. This unequivocally demonstrates that loss of imprinting represents an important additional mechanism for RB1 pathway inactivation in human HCC, complementing well-described molecular defects. Copyright (C) 2014 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.