title: CpG methylation in exon 1 of transcription factor 4 increases with age in normal gastric mucosa and is associated with gene silencing in intestinal-type gastric cancers.
abstract: Transcriptional factor 4 (TCF4), encoding a basic helix-loop-helix transcriptional factor, has recently been demonstrated as a causative gene for Pitt-Hopkins syndrome, a neurodevelopmental disease. Examination of gastric cancers using the restriction landmark genomic scanning technique revealed methylation at a NotI enzyme site in TCF4 intron 8 and further identified CpG dinucleotide hypermethylation in TCF4 exon 1, strongly associated with gene silencing in gastric cancer cell lines. Treatment with 5-aza-2'-deoxycytidine and/or trichostatin A restored TCF4 expression in TCF4-silenced gastric cancer cell lines. Real-time reverse transcription-polymerase chain reaction analysis of 77 paired primary gastric tumor samples revealed that 38% of analyzed tumors had a >2-fold decrease in TCF4 expression compared with adjacent normal-appearing tissue, and the decrease significantly correlated with increased CpG methylation in TCF4 exon 1. Clinicopathologic data showed that decreased TCF4 expression occurred significantly more frequently in intestinal-type (22/37, 59%) than in diffuse-type (7/37, 19%) gastric cancers (P = 0.0004) and likewise more frequently in early (12/18, 67%) than in advanced (17/59, 29%) gastric cancers (P = 0.004). CpG methylation markedly increased with patient age among normal-appearing tissues, suggesting that CpG methylation in gastric mucosa may be one of the earliest events in carcinogenesis of intestinal-type gastric cancers. Furthermore, ectopic expression of TCF4 decreased cell growth in a gastric cancer cell line, and the knock down of TCF4 using small interfering RNA increased cell migration. Based on these results, we propose that the observed frequent epigenetic-mediated TCF4 silencing plays a role in tumor formation and progression.
authors.affiliation: Medical Genomics Research Center, Korea Research Institute of Bioscience and Biotechnology, Department of Functional Genomics, University of Science and Technology, 52 Eoeun-dong, Yuseong-gu, Daejeon 305-806, Republic of Korea.
authors.forename: Seung-Kyoon
authors.initials: SK
authors.lastname: Kim
authors.forename: Hay-Ran
authors.initials: HR
authors.lastname: Jang
authors.forename: Jeong-Hwan
authors.initials: JH
authors.lastname: Kim
authors.forename: Mirang
authors.initials: M
authors.lastname: Kim
authors.forename: Seung-Moo
authors.initials: SM
authors.lastname: Noh
authors.forename: Kyu-Sang
authors.initials: KS
authors.lastname: Song
authors.forename: Gyeong Hoon
authors.initials: GH
authors.lastname: Kang
authors.forename: Hee Jin
authors.initials: HJ
authors.lastname: Kim
authors.forename: Seon-Young
authors.initials: SY
authors.lastname: Kim
authors.forename: Hyang-Sook
authors.initials: HS
authors.lastname: Yoo
authors.forename: Yong Sung
authors.initials: YS
authors.lastname: Kim
mesh_terms: D000375:Aging / Q000502:physiology*; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D045744:Cell Line, Tumor; D003001:Cloning, Molecular; D018899:CpG Islands / Q000502:physiology*; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000235:genetics / Q000302:isolation & purification; D004268:DNA-Binding Proteins / Q000235:genetics*; D005091:Exons; D005753:Gastric Mucosa / Q000473:pathology / Q000502:physiology*; D020868:Gene Silencing; D006801:Humans; D007414:Intestinal Neoplasms / Q000235:genetics*; D012334:RNA, Neoplasm / Q000235:genetics / Q000302:isolation & purification; D013274:Stomach Neoplasms / Q000235:genetics*; D051820:TCF Transcription Factors / Q000235:genetics*; D000073940:Transcription Factor 4; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D012334:RNA, Neoplasm; D051820:TCF Transcription Factors; C532096:TCF4 protein, human; D000073940:Transcription Factor 4; D014157:Transcription Factors