Loss of parental‐specific methylation at the IGF2 locus in human hepatocellular carcinoma

Abstract

Significant production of the growth factor IGF2 has been reported in human hepatocellular carcinomas (HCCs). Disturbances associated with changes in methylation at this locus or affecting the 11p15.5 imprinting domain as a whole can be postulated in HCCs. In the present study, the methylation status of differentially methylated regions of the imprinted genes TSSC5, LIT1, and IGF2, which span the 11p15 domain, was analysed in 71 liver tissues from virus-associated and non-virus-associated HCCs compared with six normal liver tissues. Altered methylation of TSSC5 and LIT1 was observed in only 6% and 8% of HCCs, respectively, compared with 89% at the IGF2 locus, suggesting that these loci were not concomitantly dysregulated. These observations suggest that loss of parental-specific methylation at the IGF2 locus may be specifically associated with HCC, whether virus-associated or non-virus-associated, and arising in cirrhotic or non-cirrhotic livers.

Rapid Identification of Promoter Hypermethylation in Hepatocellular Carcinoma by Pyrosequencing of Etiologically Homogeneous Sample Pools

“…The observed hypomethylation in the IGF2 DMR2 is in good concordance with previously published results studying the same region. 32 However, the published results could only distinguish globally different methylation patterns in the DMR because of the use of denaturing high-performance liquid chromatography (dHPLC) as method for read-out rather than a method with quantitative single nucleotide resolution as presented here. The slight, but consistent and significant, reduction of DNA methylation levels in the DMR2 in cirrhotic liver samples compared with normal livers, which was already detected in the pooled samples, demonstrates the quantitative resolution and power of our approach.…”

“…Here, we present a novel method that enables rapid screening for differential methylation using etiologically homogeneous pools of samples. We analyzed quantitatively the DNA methylation levels at 112 CpGs in the promoter or differentially methylated region (DMR) of five genes that have previously been found to be implicated in the pathogenesis of hepatocellular carcinoma (HCC): the cell-cycle regulator CDKN2A (p16), 30 glutathione S-transferase (GSTP1) involved in detoxification and drug resistance, 31 the insulin-like growth factor 2 (IGF2), 32 the DNA mismatch repair gene MLH1, 33 and ␤-catenin (CTNNB1), which is mutated in 26 to 40% of human HCCs and not regulated by methylation of its promoter. 34,35 Samples were grouped into pools after bisulfite treatment depending on the etiology (hepatitis B or C virus infection and alcohol consumption) and on the tumoral and nontumoral tissue status: control liver, noncirrhotic or cirrhotic adjacent nontumoral liver, hepatic adenoma, and HCC with and without ␤-catenin mutation.…”

Tumor suppressor candidate TSSC5 is regulated by UbcH6 and a novel ubiquitin ligase RING105

“…The gene cluster is conserved between human and mouse (Paulsen et al, 1998). Among the genes located in the region, mutation of the IGF2 (insulin-like growth factor 2) gene was shown to have a high correlation with Wilms' tumor (Ravenel et al, 2001), and loss of imprinting in IGF2 is associated with personal/family history of colorectal neoplasia (Cui et al, 2003) and with hepatocarcinoma (Poirier et al, 2003). However, these effects may be due to global effect on epigenetic imprinting, since IGF2 locus serves as an imprinting center (Lewis and Murrell, 2004).…”

Liver insulin-like growth factor 2 methylation in hepatitis C virus cirrhosis and further occurrence of hepatocellular carcinoma

“…Calvisi et al recently showed that the extent of genome-wide hypomethylation p r o g r e s s ive l y i n c r e a s e d f r o m n o n -n e o p l a s t i c surrounding liver to fully malignant HCC [49] , indicating that g enomic hypomethylation is an impor tant prognostic factor in HCC and opens the possibility of using molecular targets for chemoprevention or treatment of HCC. Regarding Igf2 locus, we have observed hypomethylation at Igf2 exon 8-9 in 90% (28/31) of HCV associated HCC, in contrast to the normal methylation pattern of two other genes located in the same area, the 11p15 locus [41] . This indicates that alterations in the IGF2 pathway are a pivotal event in hepatocarcinogenesis, at least in patients with HCVrelated cirrhosis.…”

“…Hypomethylation at the Igf2 locus has been found in many type of cancers, including ovarian, lung and colon [40] . In a previous study analyzing the methylation status of Igf2 DMR2 in 71 liver samples from mostly viral HCC compared to 6 normal liver samples, we observed a hypomethylated profile at the Igf2 locus in 89% of cases of HCC in contrast with the pattern observed in normal livers [41] . In addition, Cui et al [42] showed that hypomethylation of the Igf2 gene in peripheral blood lymphocytes (PBL) is associated with a predisposition to colorectal cancer, suggesting that the epigenetic alteration of Igf2 could be an early event in colorectal carcinogenesis.…”