title: Promoter hypermethylation of DNA damage response genes in hepatocellular carcinoma.
abstract: Aberrant methylation of promoter CpG islands is a major inactivation mechanism of tumour-related genes that play a crucial role in the progression of silencing in human cancers, including HCC (hepatocellular carcinoma). We have examined the promoter methylation status of five important DNA damage response genes in fresh-frozen HCC tissues and cell lines, as well as the possible correlation between methylation patterns and clinical features of the carcinoma. Promoter methylation status of RASSF1A (Ras association domain family 1), CHFR (checkpoint with forkhead and ring finger domains), GSTP1 (glutathione-S-transferase-pi gene), MGMT [O(6)-methylguanine-DNA methyltransferase] and hMLH1 (human mutL homologue 1) were examined by the MSP (methylation-specific PCR) in 70 HCC tissues and five HCC cell lines. The mRNA expression levels of these genes were measured by RT-PCR (reverse transcription-PCR). Methylation frequencies of these genes tested in HCC were 54 (78%) for RASSF1A, 30 (43%) for CHFR, 26 (38%) for GSTP1 and 22 (32%) for MGMT. No hypermethylation was detected for hMLH1 in any case of HCC or HCC cell lines. Moreover, promoter hypermethylation of RASSF1A, CHFR and GSTP1 in both HepG2 and SNU398 cells, and hypermethylation of MGMT in Huh7 cells, were detected. Treatment of three cell lines with 5Aza-dC (5-aza-20-deoxycytidine) restored or increased the expression of these genes, implicating aberrant DNA methylation in transcriptional silencing. Hypermethylation of RASSF1A and patient age were significantly associated. CHFR methylation status showed a statistically significant correlation with HCC progression. Methylation of the RASSF1A, CHFR, GSTP1 and MGMT genes seem therefore to play an important role in the pathogenesis of HCC. These epigenetic changes may have prognostic importance for patients with HCC.
authors.affiliation: Department of Infection, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450052, Peoples Republic of China.
authors.forename: Zhiqin
authors.initials: Z
authors.lastname: Li
authors.forename: Hongyan
authors.initials: H
authors.lastname: Zhang
authors.forename: Jianping
authors.initials: J
authors.lastname: Yang
authors.forename: Tielai
authors.initials: T
authors.lastname: Hao
authors.forename: Shenglei
authors.initials: S
authors.lastname: Li
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000378:metabolism* / Q000401:mortality; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D018899:CpG Islands / Q000235:genetics; D004249:DNA Damage; D019175:DNA Methylation; D015254:DNA Modification Methylases / Q000235:genetics / Q000378:metabolism; D004260:DNA Repair / Q000235:genetics*; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism; D000077209:Decitabine; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing / Q000187:drug effects; D051549:Glutathione S-Transferase pi / Q000235:genetics / Q000378:metabolism; D056945:Hep G2 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism; D008297:Male; D000070957:MutL Protein Homolog 1; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D000075223:Poly-ADP-Ribose Binding Proteins; D011379:Prognosis; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000075223:Poly-ADP-Ribose Binding Proteins; C411762:RASSF1 protein, human; D012333:RNA, Messenger; D025521:Tumor Suppressor Proteins; D000077209:Decitabine; D015254:DNA Modification Methylases; C515491:MGMT protein, human; C412002:CHFR protein, human; D044767:Ubiquitin-Protein Ligases; C496556:GSTP1 protein, human; D051549:Glutathione S-Transferase pi; D000070957:MutL Protein Homolog 1; D045643:DNA Repair Enzymes; D001374:Azacitidine