DNA Methylation Suppresses Expression of the Urea Cycle Enzyme Carbamoyl Phosphate Synthetase 1 (CPS1) in Human Hepatocellular Carcinoma
DNA Methylation Suppresses Expression of the Urea Cycle Enzyme Carbamoyl Phosphate Synthetase 1 (CPS1) in Human Hepatocellular Carcinoma
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DOI：
10.1016/j.ajpath.2010.10.023
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发表时间：
2011-02-01
影响因子：
6
通讯作者：
Liu, Chen
中科院分区：
文献类型：
--
作者：
Liu, Hongyan;Dong, Huijia;Liu, Chen
氨甲酰磷酸合成酶1（CPS 1）是尿素循环中的肝脏特异性线粒体内限速酶。先前的研究表明，CPS 1是肝细胞石蜡1抗体的抗原，肝细胞石蜡1抗体是外科病理学实践中常用的抗体;并且CPS 1表达似乎在肝癌组织和细胞系中下调。本研究的目的是了解CPS 1基因在肝癌发生中的调控。在这份报告中，我们表明，人肝细胞癌（HCC）细胞不表达CPS 1，而培养的人原代肝细胞表达丰富的水平。此外，与相应的非癌组织相比，肝肿瘤组织中CPS 1表达沉默或下调。用去甲基化剂5-氮杂胞苷恢复HCC细胞中CPS 1的表达。我们发现，位于转录起始位点附近的两个CpG二核苷酸和第一内含子中富含CpG的区域在HCC细胞中被高甲基化。与癌旁组织相比，肝癌组织中也检测到两个CpG二核苷酸的高甲基化。进一步的诱变分子分析表明，这两个CpG二核苷酸在CPS 1基因的启动子活性中起作用。总之，我们的研究表明，DNA甲基化是沉默CPS 1在人肝癌细胞中表达的关键机制，CPS 1基因的两个CpG二核苷酸的高甲基化是肝癌的潜在生物标志物。(Am J Pathol 2011，178：652-661; DOI：10.10164/j.ajpath.2010.10.023）
Carbamoyl phosphate synthetase 1 (CPS1) is a liver-specific, intramitochondrial, rate-limiting enzyme in the urea cycle. A previous study showed that CPS1 is the antigen for hepatocyte paraffin 1 antibody, a commonly used antibody in surgical pathology practice; and CPS1 expression appears to be down-regulated in liver cancer tissue and cell lines. The aim of this study is to understand how the CPS1 gene is regulated in liver carcinogenesis. In this report, we show that human hepatocellular carcinoma (HCC) cells do not express CPS1, whereas cultured human primary hepatocytes express abundant levels. In addition, CPS1 was silenced or down-regulated in liver tumor tissues compared with the matched noncancerous tissues. The expression of CPS1 in HCC cells was restored with a demethylation agent, 5-azacytidine. We show that two CpG dinucleotides, located near the transcription start site, and a CpG-rich region in the first intron were hypermethylated in HCC cells. The hypermethylation of the two CpG dinucleotides was also detected in HCC tumor tissues compared with noncancerous tissues. Further molecular analysis with mutagenesis indicated that the two CpG dinucleotides play a role in promoter activity of the CPS1 gene. In conclusion, our study demonstrates that DNA methylation is a key mechanism of silencing CPS1 expression in human HCC cells, and CPS1 gene hypermethylation of the two CpG dinucleotides is a potential biomarker for HCC. (Am J Pathol 2011, 178:652-661; DOI: 10.10164/j.ajpath.2010.10.023)