title: Association between CpG island methylation and microsatellite instability in colorectal cancer.
abstract: De novo methylation of promoter region CpG islands has been increasingly associated with transcriptional inactivation of important genes in neoplasia. To study the potential mechanisms underlying aberrant methylation in cancer, we have determined the methylation patterns of selected genes in colorectal cancers with and without microsatellite instability (MI), which results from defects in one of several base mismatch repair genes. A total of 47 colorectal cancers were analyzed, of which 15 were MI+ (32%). We now report that both the frequency and the extent of de novo methylation are strikingly increased in MI+ cancers. Hypermethylation of the p16 gene was found in 60% of MI+ cancers, compared to only 22% in MI- cancers (P = 0.02). Similarly, hypermethylation of the thrombospondin-1 (TSP-1) gene, an angiogenesis inhibitor, was increased in MI+ cancers (27% versus 0%; P = 0.008). Extensive methylation of insulin-like growth factor II (IGF2) and hypermethylated in cancer-1 (HIC-1) genes was observed in 60 and 80% of MI+ cancers, respectively, as contrasted with 6 and 38% of MI- cancers (P = 0.0002 and 0.01, respectively). Furthermore, 60% of the MI+ cancers displayed the hypermethylation events at two or more loci in a concordant manner compared to only 9% of the MI- cancers (P < 0.001). These results demonstrate a strong link between promoter hypermethylation and genetic instability due to deficient DNA repair.
authors.affiliation: The Johns Hopkins Oncology Center, and Department of Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21231, USA.
authors.forename: N
authors.initials: N
authors.lastname: Ahuja
authors.forename: A L
authors.initials: AL
authors.lastname: Mohan
authors.forename: Q
authors.initials: Q
authors.lastname: Li
authors.forename: J M
authors.initials: JM
authors.lastname: Stolker
authors.forename: J G
authors.initials: JG
authors.lastname: Herman
authors.forename: S R
authors.initials: SR
authors.lastname: Hamilton
authors.forename: S B
authors.initials: SB
authors.lastname: Baylin
authors.forename: J P
authors.initials: JP
authors.lastname: Issa
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism; D015179:Colorectal Neoplasms / Q000235:genetics*; D018899:CpG Islands / Q000235:genetics*; D019941:Cyclin-Dependent Kinase Inhibitor p16; D019175:DNA Methylation; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism; D018895:Microsatellite Repeats / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D019699:Thrombospondins
chemical_list: D002352:Carrier Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16; D008562:Membrane Glycoproteins; D019699:Thrombospondins