Hepatitis virus infection affects DNA methylation in mice with humanized livers.

Cells of tumors associated with chronic inflammation frequently have altered patterns of DNA methylation, including hepatocellular carcinomas. Chronic hepatitis has also been associated with aberrant DNA methylation, but little is known about their relationship. Pyrosequencing was used to determine the methylation status of cultured Huh7.5.1 hepatoma cells after hepatitis C virus (HCV) infection. We also studied mice with severe combined immunodeficiency carrying the urokinase-type plasminogen activator transgene controlled by an albumin promoter (urokinase-type plasminogen activator/severe combined immunodeficient mice), in which up to 85% of hepatocytes were replaced by human hepatocytes (chimeric mice). Mice were given intravenous injections of hepatitis B virus (HBV) or HCV, liver tissues were collected, and DNA methylation profiles were determined at different time points after infection. We also compared methylation patterns between paired samples of hepatocellular carcinomas and adjacent nontumor liver tissues from patients. No reproducible changes in DNA methylation were observed after infection of Huh7.5.1 cells with HCV. Livers from HBV- and HCV-infected mice had genome-wide, time-dependent changes in DNA methylation, compared with uninfected urokinase-type plasminogen activator/severe combined immunodeficient mice. There were changes in 160 ± 63 genes in HBV-infected and 237 ± 110 genes in HCV-infected mice. Methylation of 149 common genes increased in HBV- and HCV-infected mice; methylation of some of these genes also increased in hepatocellular carcinoma samples from patients compared with nontumor tissues. Expression of Ifng, which is expressed by natural killer cells, increased significantly in chimeric livers, in concordance with induction of DNA methylation, after infection with HBV or HCV. Induction of Ifng was reduced after administration of an inhibitor of natural killer cell function (anti-asialo GM1). In chimeric mice with humanized livers, infection with HBV and HCV appears to activate a natural kill cell-dependent innate immune response. This contributes to the induction and accumulation of aberrant DNA methylation in human hepatocytes.

Okamoto Y ，Shinjo K ，Shimizu Y ，Sano T ，Yamao K ，Gao W ，Fujii M ，Osada H ，Sekido Y ，Murakami S ，Tanaka Y ，Joh T ，Sato S ，Takahashi S ，Wakita T ，Zhu J ，Issa JP ，Kondo Y ... -  《-》

Aberrant DNA methylation distinguishes hepatocellular carcinoma associated with HBV and HCV infection and alcohol intake.

Hepatocellular carcinoma (HCC) is one of the most frequent human cancers and a major cause of cancer-related death worldwide. The major risk factors for developing HCC are infection by hepatitis B virus (HBV) and hepatitis C virus (HCV), chronic alcoholism, and aflatoxins; however, critical gene targets remain largely unknown. Herein, we sought to establish DNA methylation patterns in HCC and corresponding cirrhotic tissues and to identify DNA methylation changes associated with major risk factors. We have established assays for quantitative analysis of DNA methylation levels in a panel of seven cancer-associated genes and repetitive elements, and combined these assays with a series of HCC tumors, associated with major risk factors, collected from two different geographical areas. We found a high frequency of aberrant hypermethylation of specific genes (RASSF1A, GSTP1, CHRNA3, and DOK1) in HCC tumors as compared to control cirrhotic or normal liver tissues, suggesting that aberrant hypermethylation exhibits non-random and tumor-specific patterns in HCC. Importantly, our analysis revealed an association between alcohol intake and the hypomethylation of MGMT and between hypermethylation of GSTP1 and HBV infection, indicating that hypermethylation of the genes analyzed in HCC tumors exhibits remarkably distinct patterns depending on associated risk factors. This study identifies aberrant DNA methylation of specific cellular genes in HCC and the major risk factors associated with these changes, providing information that could be exploited for biomarker discovery in clinics and molecular epidemiology.

Lambert MP ，Paliwal A ，Vaissière T ，Chemin I ，Zoulim F ，Tommasino M ，Hainaut P ，Sylla B ，Scoazec JY ，Tost J ，Herceg Z ... -  《-》

Differential microRNA expression between hepatitis B and hepatitis C leading disease progression to hepatocellular carcinoma.

Ura S ，Honda M ，Yamashita T ，Ueda T ，Takatori H ，Nishino R ，Sunakozaka H ，Sakai Y ，Horimoto K ，Kaneko S ... -  《-》

Intensive hypermethylation of the CpG island of Ras association domain family 1A in hepatitis B virus-associated hepatocellular carcinomas.

Zhong S ，Yeo W ，Tang MW ，Wong N ，Lai PB ，Johnson PJ ... -  《CLINICAL CANCER RESEARCH》

p16 promoter hypermethylation in human hepatocellular carcinoma with or without hepatitis virus infection.

Epigenetic alteration through methylation is one of the most important steps in carcinogenesis. However, the relation between hepatitis virus infection and epigenetic alterations is poorly understood. Sixteen patients without hepatitis B virus (HBV) and hepatitis C virus (HCV) and 35 patients with HBV or HCV who underwent liver resection for hepatocellular carcinoma (HCC) were studied. Mutation of p53 was detected by direct sequencing. Methylation status of p16 was evaluated in tumor and noncancerous liver tissues by methylation-specific polymerase chain reaction. In HCC without HBV and HCV, p53 mutations were detected in 5 (31%) of 16 HCCs. Methylation of p16 promoter was detected in 2 (25%) of 8 moderately differentiated HCCs, 6 (75%) of 8 poorly differentiated HCCs, and none of 16 noncancerous tissue specimens. In HCC with HBV or HCV, p53 mutations were detected in 8 (23%) of 35 HCCs. Methylation of p16 promoter was detected in 2 (100%) of 2 well-differentiated HCCs, 13 (76%) of 17 moderately differentiated HCCs, 12 (75%) of 16 poorly differentiated HCCs, and 9 (26%) of 35 noncancerous liver tissue specimens. Our results suggest that hepatitis viruses might induce methylation of p16 promoter in liver with chronic inflammation, before appearance of HCC.

Narimatsu T ，Tamori A ，Koh N ，Kubo S ，Hirohashi K ，Yano Y ，Arakawa T ，Otani S ，Nishiguchi S ... -  《-》