title: Age-related hypermethylation of the 5' region of MLH1 in normal colonic mucosa is associated with microsatellite-unstable colorectal cancer development.
abstract: Hypermethylation of the MLH1 promoter underlies most sporadic colorectal cancers with microsatellite instability (MSI). To investigate the role of hypermethylation in the normal colonic mucosa as a possible precursor lesion, we studied 700 bp upstream of MLH1 covering 51 CpG sites. We found partially methylated alleles in 15 of 34 (44%) patients <60 years of age and 20 of 24 (83%) patients > or =80 years of age (P = 0.0026). Fully methylated alleles were present in 18 of 33 (55%) patients with MSI+ tumors but in only 18 of 90 (20%) patients with MSI- tumors (P = 0.00019). By in situ analysis, methylation was patchy and located mainly in the cryptal regions close to the lumen. We conclude that the spread of methylation in the MLH1 promoter in the normal colonic mucosa is closely associated with age and the development of sporadic MSI+ colorectal cancers.
authors.affiliation: Division of Human Cancer Genetics, Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: H
authors.initials: H
authors.lastname: Nakagawa
authors.forename: G J
authors.initials: GJ
authors.lastname: Nuovo
authors.forename: E E
authors.initials: EE
authors.lastname: Zervos
authors.forename: E W
authors.initials: EW
authors.lastname: Martin
authors.forename: R
authors.initials: R
authors.lastname: Salovaara
authors.forename: L A
authors.initials: LA
authors.lastname: Aaltonen
authors.forename: A
authors.initials: A
authors.lastname: de la Chapelle
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002352:Carrier Proteins; D003106:Colon / Q000502:physiology*; D015179:Colorectal Neoplasms / Q000235:genetics*; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000235:genetics; D019175:DNA Methylation; D006801:Humans; D017403:In Situ Hybridization / Q000379:methods; D007413:Intestinal Mucosa / Q000502:physiology*; D018895:Microsatellite Repeats / Q000235:genetics*; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D009363:Neoplasm Proteins / Q000235:genetics*; D009687:Nuclear Proteins; D016133:Polymerase Chain Reaction / Q000379:methods; D011230:Precancerous Conditions / Q000235:genetics*; D011401:Promoter Regions, Genetic; D017422:Sequence Analysis, DNA
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000070957:MutL Protein Homolog 1