title: LINE-1 and Alu methylation patterns in lymph node metastases of head and neck cancers.
abstract: BACKGROUND
  The potential use of hypomethylation of Long INterspersed Element 1 (LINE-1) and Alu elements (Alu) as a biomarker has been comprehensively assessed in several cancers, including head and neck squamous cell carcinoma (HNSCC). Failure to detect occult metastatic head and neck tumors on radical neck lymph node dissection can affect the therapeutic measures taken.
  
  
  OBJECTIVE
  The aim of this study was to investigate the LINE-1 and Alu methylation status and determine whether it can be applied for detection of occult metastatic tumors in HNSCC cases.
  
  
  METHODS
  We used the Combine Bisulfite Restriction Analysis (COBRA) technique to analyse LINE-1 and Alu methylation status. In addition to the methylation level, LINE-1 and Alu loci were classified based on the methylation statuses of two CpG dinucleotides in each allele as follows: hypermethylation (mCmC), hypomethylation (uCuC), and 2 forms of partial methylation (mCuC and uCmC). Sixty-one lymph nodes were divided into 3 groups: 1) non-metastatic head and neck cancer (NM), 2) histologically negative for tumor cells of cases with metastatic head and neck cancer (LN), and 3) histologically positive for tumor cells (LP).
  
  
  RESULTS
  Alu methylation change was not significant. However, LINE-1 methylation of both LN and LP was altered, as demonstrated by the lower LINE-1 methylation levels (p<0.001), higher percentage of mCuC (p<0.01), lower percentage of uCmC (p<0.001) and higher percentage of uCuC (p<0.001). Using receiver operating characteristic (ROC) curve analysis, %uCmC and %mCuC values revealed a high level of AUC at 0.806 and 0.716, respectively, in distinguishing LN from NM.
  
  
  CONCLUSIONS
  The LINE-1 methylation changes in LN have the same pattern as that in LP. This epigenomic change may be due to the presence of occult metastatic tumor in LN cases.
authors.affiliation: Department of Oral and Maxillofacial Pathology, Faculty of Dentistry, Mahidol University, Bangkok, Thailand. trcskl@gmail.com
authors.forename: Nakarin
authors.initials: N
authors.lastname: Kitkumthorn
authors.forename: Somboon
authors.initials: S
authors.lastname: Keelawat
authors.forename: Prakasit
authors.initials: P
authors.lastname: Rattanatanyong
authors.forename: Apiwat
authors.initials: A
authors.lastname: Mutirangura
mesh_terms: D000483:Alleles; D020087:Alu Elements; D019540:Area Under Curve; D014408:Biomarkers, Tumor / Q000235:genetics*; D002294:Carcinoma, Squamous Cell / Q000175:diagnosis / Q000235:genetics* / Q000556:secondary*; D019175:DNA Methylation; D006258:Head and Neck Neoplasms / Q000175:diagnosis / Q000235:genetics* / Q000473:pathology*; D006801:Humans; D020084:Long Interspersed Nucleotide Elements; D008207:Lymphatic Metastasis; D012372:ROC Curve
chemical_list: D014408:Biomarkers, Tumor