Aberrant methylation of multiple tumor suppressor genes in aging liver, chronic hepatitis, and hepatocellular carcinoma

Abstract

Aberrant DNA methylation is an important epigenetic alteration in hepatocellular carcinoma (HCC). However, the molecular processes underlying the methylator phenotype and the contribution of hepatitis viruses are poorly understood. The current study is a comprehensive methylation analysis of human liver tissue specimens. A total of 176 liver tissues, including 77 pairs of HCCs and matching noncancerous liver and 22 normal livers, were analyzed for methylation. Methylation of 19 epigenetic markers was quantified, and the results were correlated with different disease states and the presence or absence of hepatitis B virus (HBV) and hepatitis C virus (HCV) infections. Based on methylation profiles, the 19 loci were categorized into 3 groups. Normal liver tissues showed methylation primarily in group 1 loci (HIC-1, CASP8, GSTP1, SOCS1, RASSF1A, p16, APC), which was significantly higher than group 2 (CDH1, RUNX3, RIZ1, SFRP2, MINT31) and group 3 markers (COX2, MINT1, CACNA1G, RASSF2, MINT2, Reprimo, DCC) (P < 0.0001). Noncancerous livers demonstrated increased methylation in both group 1 and group 2 loci. Methylation was significantly more abundant in HCV-positive livers compared with normal liver tissues. Conversely, HCC showed frequent methylation at each locus investigated in all 3 groups. However, the group 3 loci showed more dense and frequent methylation in HCV-positive cancers compared with both HBV-positive cancers and virus-negative cancers (P < 0.0001). Conclusion: Methylation in HCC is frequent but occurs in a gene-specific and disease-specific manner. Methylation profiling allowed us to determine that aberrant methylation is commonly present in normal aging livers, and sequentially progresses with advancing stages of chronic viral infection. Finally, our data provide evidence that HCV infection may accelerate the methylation process and suggests a continuum of increasing methylation with persistent viral infection and carcinogenesis in the liver. (HEPATOLOGY 2008;47:908-918.)

The Tumor Suppressor Gene Hypermethylated in Cancer 1 Is Transcriptionally Regulated by E2F1

“…Importantly,hypermethylation of the P0 promoter is sufficient to silence HIC1 expression (28). In line with our methylation results, two studies measured HIC1 promoter hypermethylation in different morphologic grades of the liver and found increasing HIC1 promoter methylation from normal liver tissue, to precancerous liver tissue (showing chronic hepatitis or cirrhosis), to primary hepatocellular carcinoma, but no significant correlation between hypermethylation and HIC1 mRNA expression levels was seen (4,5). These results indicate that mechanisms other than hypermethylation contribute to the low HIC1 expression seen in hepatocellular carcinoma.…”

“…example in primary human hepatocellular carcinomas (4,5). Of note, it was shown that in most cell lines, dense methylation of the HIC1 P0 promoter was sufficient to completely silence HIC1 mRNA expresssion.…”

“…Chromosome 17 is frequently altered in human cancers and its allelic loss at the p53 locus is often combined with mutations of the remaining p53 allele. Interestingly, the 17p13.3 region is frequently deleted or hypermethylated in human cancers, such as breast cancer (2), colorectal cancer (3), and hepatocellular carcinomas (4,5). Moreover, hypermethylation in this chromosomal region often leads to inhibition of HIC1 expression, and overexpression of HIC1 in different cancer cell lines decreases their clonogenic survival (6).…”

Methylation of multiple genes as molecular markers for diagnosis of a small, well‐differentiated hepatocellular carcinoma

“…In this regard, known methylated genes, including SOCS1 and HIC-1, may prove unsuitable for HCC diagnosis due to their high methylation rate in non-tumor liver tissues. 35 In the present study, only SPINT2 showed a complete lack of synchronized methylation trend between HCC and non-tumor tissues, suggesting that it may be highly and more specifically methylated in HCC than the other 6 genes examined in this study. This novel finding obtained from our detailed methylation analysis supports the use of SPINT2 as a molecular marker for HCC.…”

Altered mucosal DNA methylation in parallel with highly active Helicobacter pylori-related gastritis

“…4 Methylation levels of the promoter CpG islands of six genes in the corpus region of the gastric mucosae according to serum H. pylori antibody titer. Compared to the H. pylori-negative group, the methylation level was consistently increased in a stepwise manner in the low-and high-titer groups (p \ 0.05) viral hepatitis, UC, and H. pylori-related gastritis [32][33][34]. However, attention has rarely been paid to the correlations between the degree of altered DNA methylation and activity of inflammation, probably because of difficulties in quantitatively evaluating inflammation in tissues.…”