title: Alu hypomethylation in smoke-exposed epithelia and oral squamous carcinoma.
abstract: BACKGROUND
  Alu elements are one of the most common repetitive sequences that now constitute more than 10% of the human genome and potential targets for epigenetic alterations. Correspondingly, methylation of these elements can result in a genome-wide event that may have an impact in cancer. However, studies investigating the genome-wide status of Alu methylation in cancer remain limited.
  
  
  OBJECTIVE
  Oral squamous cell carcinoma (OSCC) presents with high incidence in South-East Asia and thus the aim of this study was to evaluate the Alu methylation status in OSCCs and explore with the possibility of using this information for diagnostic screening. We evaluated Alu methylation status in a) normal oral mucosa compared to OSCC; b) peripheral blood mononuclear cells (PBMCs) of normal controls comparing to oral cancer patients; c) among oral epithelium of normal controls, smokers and oral cancer patients.
  
  
  METHODS
  Alu methylation was detected by combined bisulfite restriction analysis (COBRA) at 2 CpG sites. The amplified products were classified into three patterns; hypermethylation ((m)C(m)C), partial methylation (uC(m)C+(m)C(u)C), and hypomethylation ((u)C(u)C).
  
  
  RESULTS
  The results demonstrate that the %(m)C(m)C value is suitable for differentiating normal and cancer in oral tissues (p=0.0002), but is not significantly observe in PBMCs. In addition, a stepwise decrease in this value was observed in the oral epithelium from normal, light smoker, heavy smoker, low stage and high stage OSCC (p=0.0003). Furthermore, receiver operating characteristic (ROC) curve analyses demonstrated the potential of combined %mC or %(m)C(m)C values as markers for oral cancer detection with sensitivity and specificity of 86.7% and 56.7%, respectively.
  
  
  CONCLUSIONS
  Alu hypomethylation is likely to be associated with multistep oral carcinogenesis, and might be developed as a screening tool for oral cancer detection.
authors.affiliation: Department of Anatomy, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand E-mail : Skeskanya@gmail.com, Nakarinkit@gmail.com.
authors.forename: Charoenchai
authors.initials: C
authors.lastname: Puttipanyalears
authors.forename: Keskanya
authors.initials: K
authors.lastname: Subbalekha
authors.forename: Apiwat
authors.initials: A
authors.lastname: Mutirangura
authors.forename: Nakarin
authors.initials: N
authors.lastname: Kitkumthorn
mesh_terms: D000328:Adult; D020087:Alu Elements / Q000235:genetics*; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000473:pathology; D016022:Case-Control Studies; D015331:Cohort Studies; D019175:DNA Methylation; D004848:Epithelium / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009061:Mouth Mucosa / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D009062:Mouth Neoplasms / Q000235:genetics* / Q000473:pathology; D009367:Neoplasm Staging; D011379:Prognosis; D012372:ROC Curve; D012907:Smoking / Q000009:adverse effects*