title: Demethylation of the region around exon 2 of MLH1 gene in gastrointestinal cancer.
abstract: OBJECTIVE
  Our previous study showed that methylation of the mutL homolog 1 (MLH1) promoter may spread upstream from the Alu elements in intron 1. In this study, we investigated if the Alu methylation could also spread downstream.
  
  
  METHODS
  Two colorectal cancer cell lines (RKO, SW48), and four colorectal and three gastric carcinomas [all Microsatellite Instability (MSI)-positive] were selected as cases. Normal colorectal and gastric mucosa and human peripheral blood, and one MSI-negative colorectal cancer case served as controls. After extraction of DNA, bisulfite genomic sequencing was used to analyze the methylation level of exon 2 and the adjacent part of intron 2 of the MLH1 gene.
  
  
  RESULTS
  Exon 2 and the partial intron 2 exhibited a high level of methylation in controls. In contrast, demethylation in these regions was seen in gastrointestinal cancer.
  
  
  CONCLUSIONS
  Exon 2 methylation is not likely to influence MLH1 gene expression. It seems that de-methylation of exon 2 and intron 2, in combination with intron 1, is associated with methylation spreading of the MLH1 promoter. The region around exon 2 could possibly bind proteins that regulate methylation, and therefore affect gene expression.
authors.affiliation: Department of Medical Genetics, Tongji Medical College, Huazhong University of Science and Technology, Hangkong Lu 13, Wuhan, Hubei 430030, China.
authors.forename: Yanping
authors.initials: Y
authors.lastname: Tang
authors.forename: Cong
authors.initials: C
authors.lastname: Liu
authors.forename: Xiyin
authors.initials: X
authors.lastname: Wang
authors.forename: Dong
authors.initials: D
authors.lastname: Liu
authors.forename: Sigurdur
authors.initials: S
authors.lastname: Ingvarsson
authors.forename: Huiping
authors.initials: H
authors.lastname: Chen
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D019175:DNA Methylation / Q000235:genetics*; D005091:Exons; D005770:Gastrointestinal Neoplasms / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D006801:Humans; D000070957:MutL Protein Homolog 1; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C501486:MLH1 protein, human; D009687:Nuclear Proteins; D000070957:MutL Protein Homolog 1