title: Transcriptional silencing of the DLC-1 tumor suppressor gene by epigenetic mechanism in gastric cancer cells.
abstract: DLC-1 (deleted in liver cancer) gene is frequently deleted in hepatocellular carcinoma. However, little is known about the genetic status and the expression of this gene in gastric cancer. In this study, Northern and Southern analysis showed that seven of nine human gastric cancer cell lines did not express DLC-1 mRNA, but contained the DLC-1 gene. To identify the mechanism of the loss of DLC-1 mRNA expression in these cell lines, we investigated the methylation status of DLC-1 gene by using methylation-specific PCR (MSP) and Southern blot, and found that five of seven DLC-1 nonexpressing gastric cancer cell lines were methylated in the DLC-1 CpG island. Treatment with 5-aza-2'-deoxycytidine (5-Aza-dC) induced DLC-1 mRNA expression in the gastric cancer cell lines that have the methylated alleles. Studies using SNU-601 cell line with methylated DLC-1 alleles revealed that nearly all CpG sites within DLC-1 CpG island were methylated, and that the in vitro methylation of the DLC-1 promoter region is enough to repress DLC-1 mRNA expression, regardless of the presence of transcription factors capable of inducing this gene. In all, 29 of 97 (30%) primary gastric cancers were also shown to be methylated, demonstrating that methylation of the DLC-1 CpG island is not uncommon in gastric cancer. In addition, we demonstrated that DLC-1 mRNA expression was induced, and an increase in the level of acetylated H3 and H4 was detected by the treatment with trichostatin A (TSA) in two DLC-1 nonexpressing cell lines that have the unmethylated alleles. Taken together, the results of our study suggest that the transcriptional silencing of DLC-1, by epigenetic mechanism, may be involved in gastric carcinogenesis.
authors.affiliation: National Research Laboratory for Cancer Epigenetics, Cancer Research Institute, Seoul National University College of Medicine, Seoul 110-744, Korea.
authors.forename: Tai Young
authors.initials: TY
authors.lastname: Kim
authors.forename: Hyun-Soon
authors.initials: HS
authors.lastname: Jong
authors.forename: Sang-Hyun
authors.initials: SH
authors.lastname: Song
authors.forename: Alexandre
authors.initials: A
authors.lastname: Dimtchev
authors.forename: Sook-Jung
authors.initials: SJ
authors.lastname: Jeong
authors.forename: Jung Weon
authors.initials: JW
authors.lastname: Lee
authors.forename: Tae-You
authors.initials: TY
authors.lastname: Kim
authors.forename: Noe Kyeong
authors.initials: NK
authors.lastname: Kim
authors.forename: Mira
authors.initials: M
authors.lastname: Jung
authors.forename: Yung-Jue
authors.initials: YJ
authors.lastname: Bang
mesh_terms: D000107:Acetylation / Q000187:drug effects; D000123:Acetyltransferases / Q000037:antagonists & inhibitors; D000483:Alleles; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D015152:Blotting, Northern; D015139:Blotting, Southern; D018899:CpG Islands; D019175:DNA Methylation / Q000187:drug effects; D000077209:Decitabine; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020690:GTPase-Activating Proteins; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D020868:Gene Silencing / Q000502:physiology*; D016147:Genes, Tumor Suppressor; D051548:Histone Acetyltransferases; D006657:Histones / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000235:genetics*; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D012334:RNA, Neoplasm / Q000096:biosynthesis / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000037:antagonists & inhibitors; D013274:Stomach Neoplasms / Q000235:genetics* / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics*
chemical_list: C112352:DLC1 protein, human; D004791:Enzyme Inhibitors; D020690:GTPase-Activating Proteins; D006657:Histones; D006877:Hydroxamic Acids; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D029701:Saccharomyces cerevisiae Proteins; D025521:Tumor Suppressor Proteins; C012589:trichostatin A; D000077209:Decitabine; D000123:Acetyltransferases; D051548:Histone Acetyltransferases; D001374:Azacitidine