title: Promoter Hypermethylation Profiling Identifies Subtypes of Head and Neck Cancer with Distinct Viral, Environmental, Genetic and Survival Characteristics.
abstract: BACKGROUND
  Epigenetic and genetic alteration plays a major role to the development of head and neck squamous cell carcinoma (HNSCC). Consumption of tobacco (smoking/chewing) and human papilloma virus (HPV) are also associated with an increase the risk of HNSCC. Promoter hypermethylation of the tumor suppression genes is related with transcriptional inactivation and loss of gene expression. We investigated epigenetic alteration (promoter methylation of tumor-related genes/loci) in tumor tissues in the context of genetic alteration, viral infection, and tobacco exposure and survival status.
  
  
  METHODS
  The study included 116 tissue samples (71 tumor and 45 normal tissues) from the Northeast Indian population. Methylation specific polymerase chain reaction (MSP) was used to determine the methylation status of 10 tumor-related genes/loci (p16, DAPK, RASSF1, BRAC1, GSTP1, ECAD, MLH1, MINT1, MINT2 and MINT31). Polymorphisms of CYP1A1, GST (M1 & T1), XRCC1and XRCC2 genes were studied by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and multiplex-PCR respectively.
  
  
  RESULTS
  Unsupervised hierarchical clustering analysis based on methylation pattern had identified two tumor clusters, which significantly differ by CpG island methylator phenotype (CIMP), tobacco, GSTM1, CYP1A1, HPV and survival status. Analyzing methylation of genes/loci individually, we have found significant higher methylation of DAPK, RASSF1, p16 and MINT31 genes (P = 0.031, 0.013, 0.031 and 0.015 respectively) in HPV (+) cases compared to HPV (-). Furthermore, a CIMP-high and Cluster-1 characteristic was also associated with poor survival.
  
  
  CONCLUSIONS
  Promoter methylation profiles reflecting a correlation with tobacco, HPV, survival status and genetic alteration and may act as a marker to determine subtypes and patient outcome in HNSCC.
authors.affiliation: Molecular Medicine Laboratory, Department of Biotechnology,Assam University, Silchar, Pin-788011, Assam, India.
authors.forename: Javed Hussain
authors.initials: JH
authors.lastname: Choudhury
authors.affiliation: Molecular Medicine Laboratory, Department of Biotechnology,Assam University, Silchar, Pin-788011, Assam, India.
authors.forename: Sankar Kumar
authors.initials: SK
authors.lastname: Ghosh
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000401:mortality; D019175:DNA Methylation / Q000235:genetics*; D004260:DNA Repair / Q000235:genetics; D057890:Epigenomics; D005260:Female; D006258:Head and Neck Neoplasms / Q000235:genetics* / Q000401:mortality; D006801:Humans; D007194:India; D008297:Male; D008875:Middle Aged; D060885:Multiplex Polymerase Chain Reaction; D030361:Papillomavirus Infections; D012150:Polymorphism, Restriction Fragment Length; D020641:Polymorphism, Single Nucleotide; D011401:Promoter Regions, Genetic / Q000235:genetics*; D000077195:Squamous Cell Carcinoma of Head and Neck; D064424:Tobacco Use; D055815:Young Adult