title: DNA methylation profiling revealed promoter hypermethylation-induced silencing of p16, DDAH2 and DUSP1 in primary oral squamous cell carcinoma.
abstract: BACKGROUND
  Hypermethylation in promoter regions of genes might lead to altered gene functions and result in malignant cellular transformation. Thus, biomarker identification for hypermethylated genes would be very useful for early diagnosis, prognosis, and therapeutic treatment of oral squamous cell carcinoma (OSCC). The objectives of this study were to screen and validate differentially hypermethylated genes in OSCC and correlate the hypermethylation-induced genes with demographic, clinocopathological characteristics and survival rate of OSCC.
  
  
  METHODS
  DNA methylation profiling was utilized to screen the differentially hypermethylated genes in OSCC. Three selected differentially-hypermethylated genes of p16, DDAH2 and DUSP1 were further validated for methylation status and protein expression. The correlation between demographic, clinicopathological characteristics, and survival rate of OSCC patients with hypermethylation of p16, DDAH2 and DUSP1 genes were analysed in the study.
  
  
  RESULTS
  Methylation profiling demonstrated 33 promoter hypermethylated genes in OSCC. The differentially-hypermethylated genes of p16, DDAH2 and DUSP1 revealed positivity of 78%, 80% and 88% in methylation-specific polymerase chain reaction and 24% and 22% of immunoreactivity in DDAH2 and DUSP1 genes, respectively. Promoter hypermethylation of p16 gene was found significantly associated with tumour site of buccal, gum, tongue and lip (P=0.001). In addition, DDAH2 methylation level was correlated significantly with patients' age (P=0.050). In this study, overall five-year survival rate was 38.1% for OSCC patients and was influenced by sex difference.
  
  
  CONCLUSIONS
  The study has identified 33 promoter hypermethylated genes that were significantly silenced in OSCC, which might be involved in an important mechanism in oral carcinogenesis. Our approaches revealed signature candidates of differentially hypermethylated genes of DDAH2 and DUSP1 which can be further developed as potential biomarkers for OSCC as diagnostic, prognostic and therapeutic targets in the future.
authors.affiliation: 1. Centre of Studies for Preclinical Science, Faculty of Dentistry, Universiti Teknologi MARA, Shah Alam. Selangor, Malaysia. ; 2. Institute of Medical Molecular Biotechnology, Faculty of Medicine, Universiti Teknologi MARA, Selangor, Malaysia. ; 3. Oral Cancer Research and Coordinating Center, Faculty of Dentistry, University of Malaya, Kuala Lumpur, Malaysia. ; 8. Laboratory of Biomedical Science and Molecular Microbiology, UMBIO Cluster, Institute of Postgraduate, University of Malaya, Kuala Lumpur, Malaysia.
authors.forename: Goot Heah
authors.initials: GH
authors.lastname: Khor
authors.forename: Gabriele Ruth Anisah
authors.initials: GR
authors.lastname: Froemming
authors.forename: Rosnah Binti
authors.initials: RB
authors.lastname: Zain
authors.forename: Mannil Thomas
authors.initials: MT
authors.lastname: Abraham
authors.forename: Effat
authors.initials: E
authors.lastname: Omar
authors.forename: Su Keng
authors.initials: SK
authors.lastname: Tan
authors.forename: Aik Choon
authors.initials: AC
authors.lastname: Tan
authors.forename: Vui King
authors.initials: VK
authors.lastname: Vincent-Chong
authors.forename: Kwai Lin
authors.initials: KL
authors.lastname: Thong
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000581:Amidohydrolases / Q000235:genetics*; D014408:Biomarkers, Tumor; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000473:pathology; D019941:Cyclin-Dependent Kinase Inhibitor p16; D019175:DNA Methylation; D054638:Dual Specificity Phosphatase 1 / Q000235:genetics*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D008875:Middle Aged; D009062:Mouth Neoplasms / Q000235:genetics* / Q000473:pathology; D009363:Neoplasm Proteins / Q000235:genetics*; D009367:Neoplasm Staging; D011401:Promoter Regions, Genetic; D016019:Survival Analysis
chemical_list: D014408:Biomarkers, Tumor; C000614131:CDKN2A protein, human; D019941:Cyclin-Dependent Kinase Inhibitor p16; D009363:Neoplasm Proteins; C517019:DUSP1 protein, human; D054638:Dual Specificity Phosphatase 1; D000581:Amidohydrolases; C059999:dimethylargininase
keywords: DDAH2; DNA methylation profiling; DUSP1; Oral Squamous Cell Carcinoma; promoter hypermethylation; protein expression.