title: High-risk oral leukoplakia is associated with aberrant promoter methylation of multiple genes.
abstract: Early detection of oral squamous cell carcinomas (OSCCs) is urgently needed to improve the prognosis and quality of life (QOL) of patients. Oral leukoplakias (OLs), known as the most common premalignant lesions in the oral cavity, often precede OSCCs. Especially, OLs with dysplasia are known to have a high risk of malignant transformation. Here, we searched for the promoter methylation characteristic of high-risk OLs.
  
  
  
  To identify methylation-silenced genes, a combined analysis of methylated DNA immunoprecipitation (MeDIP) - CpG island (CGI) microarray analysis and expression microarray analysis after treatment with a demethylating agent was performed in two OSCC cell lines (Ca9-22 and HSC-2). The methylation statuses of each gene were examined by methylation-specific PCR.
  
  
  
  A total of 52 genes were identified as candidates for methylation-silenced genes in Ca9-22 or HSC-2. The promoter regions of 13 genes among the 15 genes randomly selected for further analysis were confirmed to be methylated in one or more of five cell lines. In OSCC tissues (n = 26), 8 of the 13 genes, TSPYL5, EGFLAM, CLDN11, NKX2-3, RBP4, CMTM3, TRPC4, and MAP6, were methylated. In OL tissues (n = 24), seven of the eight genes, except for EGFLAM, were found to be methylated in their promoter regions. There were significantly greater numbers of methylated genes in OLs with dysplasia than in those without dysplasia (p < 0.0001).
  
  
  
  OLs at high risk for malignant transformation were associated with aberrant promoter methylation of multiple genes.
authors.affiliation: Department of Oral & Maxillofacial Surgery, University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan. abem-ora@h.u-tokyo.ac.jp.|Division for Health Service Promotion, University of Tokyo, Tokyo, Japan. abem-ora@h.u-tokyo.ac.jp.
authors.forename: Masanobu
authors.initials: M
authors.lastname: Abe
authors.affiliation: Division of Epigenomics, National Cancer Center Research Institute, Tokyo, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yamashita
authors.affiliation: Department of Dentistry, Oral & Maxillofacial Surgery, Jichi Medical University, Tochigi, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Mori
authors.affiliation: Department of Oral & Maxillofacial Surgery, University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Abe
authors.affiliation: Department of Oral & Maxillofacial Surgery, University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
authors.forename: Hideto
authors.initials: H
authors.lastname: Saijo
authors.affiliation: Department of Oral & Maxillofacial Surgery, University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
authors.forename: Kazuto
authors.initials: K
authors.lastname: Hoshi
authors.affiliation: Division of Epigenomics, National Cancer Center Research Institute, Tokyo, Japan.
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Ushijima
authors.affiliation: Department of Oral & Maxillofacial Surgery, University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Takato
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000473:pathology; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D019175:DNA Methylation / Q000235:genetics*; D055088:Early Detection of Cancer / Q000379:methods; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D047468:Immunoprecipitation; D007972:Leukoplakia, Oral / Q000235:genetics* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics*; D059467:Transcriptome
keywords: Gene silencing; Methylation; Oral leukoplakia; Oral squamous cell carcinoma; Promoter methylation