title: DNA hypermethylation on multiple CpG islands associated with increased DNA methyltransferase DNMT1 protein expression during multistage urothelial carcinogenesis.
abstract: OBJECTIVE
  We elucidated the significance of aberrant DNA methylation on multiple CpG islands and its correlation with DNA methyltransferase DNMT1 protein expression during urothelial carcinogenesis.
  
  
  METHODS
  We examined the DNA methylation status on multiple CpG islands by methylation specific polymerase chain reaction and combined bisulfite restriction enzyme analysis in 12 specimens of normal urothelium, 23 of noncancerous urothelium showing no remarkable histological changes obtained from patients with bladder cancer (NBC) and 70 of transitional cell carcinoma (TCC).
  
  
  RESULTS
  DNA methylation on CpG islands of the p16 (0%, 17% and 21%) and death-associated protein kinase (13%, 33% and 29%) genes, and methylated in tumor-2 (56%, 60% and 76%), 12 (0%, 6% and 30%), 25 (25%, 27% and 35%) and 31 (45%, 56% and 79%) clones was detected in normal urothelium, NBCs and TCCs, respectively. The incidence of concurrent DNA hypermethylation on 3 or more CpG islands in NBCs (38%) was significantly higher than that in normal urothelium (0%, p = 0.0455) and even higher in TCCs (59%, p = 0.0043). The incidence of the CpG island methylator phenotype in nonpapillary carcinomas (nodular invasive carcinomas and their precursors, ie flat carcinoma in situ, 71%) was significantly higher than in papillary carcinomas (40%, p = 0.0143). In all specimens examined concurrent DNA hypermethylation on 3 or more CpG islands significantly correlated with immunohistochemically evaluated DNMT1 protein over expression (p = 0.0167).
  
  
  CONCLUSIONS
  DNA hypermethylation on multiple CpG islands in association with DNMT1 protein over expression may participate in multistage urothelial carcinogenesis even at the precancerous stage and particularly in the development of nodular invasive carcinomas of the bladder.
authors.affiliation: Pathology Division, National Cancer Center Research Institute, Department of Urology, Faculty of Medicine, Tokyo University, Tokyo, Japan.
authors.forename: Tohru
authors.initials: T
authors.lastname: Nakagawa
authors.forename: Yae
authors.initials: Y
authors.lastname: Kanai
authors.forename: Saori
authors.initials: S
authors.lastname: Ushijima
authors.forename: Tadaichi
authors.initials: T
authors.lastname: Kitamura
authors.forename: Tadao
authors.initials: T
authors.lastname: Kakizoe
authors.forename: Setsuo
authors.initials: S
authors.lastname: Hirohashi
mesh_terms: D002295:Carcinoma, Transitional Cell / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D018899:CpG Islands / Q000235:genetics*; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000096:biosynthesis*; D019175:DNA Methylation; D006801:Humans; D001749:Urinary Bladder Neoplasms / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D019459:Urothelium / Q000378:metabolism / Q000473:pathology
chemical_list: D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human