title: Krüppel-like factor 4 expression in oral carcinoma cells and hypermethylation at the gene promoter.
abstract: BACKGROUND
  Krüppel-like factor 4 (KLF4) is a transcription factor regulating proliferation-differentiation balance of epithelium, and down-regulated in less-differentiated and advanced oral carcinomas. Although the expression is inactivated by the promoter hypermethylation in malignant tumor cells, it remains unknown in oral carcinoma cells.
  
  
  METHODS
  Genomic DNA isolated from nine different oral carcinoma cell lines and a normal keratinocyte line was treated with sodium bisulfite, and methylation at KLF4 gene promoter was determined by PCR direct-sequence analysis. KLF4 expression in cells cultured with or without demethylation reagent was monitored by quantitative real-time PCR and immunoblot.
  
  
  RESULTS
  A 237-bp promoter region spanning - 718 and - 482 of KLF4 gene was hypermethylated in oral carcinoma cells that express KLF4 at a low level, but the methylation was infrequent in cells expressing KLF4 high amount. The downstream region from - 481 to +192 was not methylated in any cell lines. Demethylation treatment of cells up-regulated the expression at mRNA and protein levels.
  
  
  CONCLUSIONS
  This study demonstrated that hypermethylation at a narrow range of the promoter region down-regulates KLF4 expression, and suggests that the loss of expression by the hypermethylation contributes to oral carcinoma progression.
authors: School of Life Dentistry at Tokyo, The Nippon Dental University, 1-9-20, Chiyoda-ku, Fujimi, Tokyo, 102-8159, Japan. ayumi.y.ii.may.seven1@gmail.com.
authors: Ayumi
authors: A
authors: Yamaguchi
authors: School of Life Dentistry at Tokyo, The Nippon Dental University, 1-9-20, Chiyoda-ku, Fujimi, Tokyo, 102-8159, Japan. kyun1096@yahoo.co.jp.
authors: Karen
authors: K
authors: Kuroyama
authors: School of Life Dentistry at Tokyo, The Nippon Dental University, 1-9-20, Chiyoda-ku, Fujimi, Tokyo, 102-8159, Japan. rococo15milktea@gmail.com.
authors: Ayana
authors: A
authors: Tokura
authors: School of Life Dentistry at Tokyo, The Nippon Dental University, 1-9-20, Chiyoda-ku, Fujimi, Tokyo, 102-8159, Japan. masuzushimango@yahoo.co.jp.
authors: Atsushi
authors: A
authors: Saito
authors: School of Life Dentistry at Tokyo, The Nippon Dental University, 1-9-20, Chiyoda-ku, Fujimi, Tokyo, 102-8159, Japan. americanfootboll4223@yahoo.co.jp.
authors: Huhga
authors: H
authors: Arikawa
authors: School of Life Dentistry at Tokyo, The Nippon Dental University, 1-9-20, Chiyoda-ku, Fujimi, Tokyo, 102-8159, Japan. soccer.hasebe@gmail.com.
authors: Takahisa
authors: T
authors: Hasebe
authors: School of Life Dentistry at Tokyo, The Nippon Dental University, 1-9-20, Chiyoda-ku, Fujimi, Tokyo, 102-8159, Japan. daiusui1992@yahoo.co.jp.
authors: Dai
authors: D
authors: Usui
authors: Department of Biochemistry, School of Life Dentistry at Tokyo, The Nippon Dental University, 1-9-20 Chiyoda-ku, Fujimi, Tokyo, 102-8159, Japan. kyama@tky.ndu.ac.jp.
authors: Kosuke
authors: K
authors: Yamaguchi
authors: Department of Biochemistry, School of Life Dentistry at Tokyo, The Nippon Dental University, 1-9-20 Chiyoda-ku, Fujimi, Tokyo, 102-8159, Japan. tchiba@tky.ndu.ac.jp.
authors: Tadashige
authors: T
authors: Chiba
authors: Department of Biochemistry, School of Life Dentistry at Tokyo, The Nippon Dental University, 1-9-20 Chiyoda-ku, Fujimi, Tokyo, 102-8159, Japan. kimai@tky.ndu.ac.jp.
authors: Kazushi
authors: K
authors: Imai
mesh_terms: D002277:Carcinoma / Q000378:metabolism; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D019175:DNA Methylation; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors / Q000378:metabolism*; D009062:Mouth Neoplasms / Q000378:metabolism*; D011401:Promoter Regions, Genetic
chemical_list: C000715467:KLF4 protein, human; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors