title: Tumor suppressor activity and inactivation of galanin receptor type 2 by aberrant promoter methylation in head and neck cancer.
abstract: BACKGROUND
  There is accumulating evidence that galanin receptors (GALRs) may be tumor suppressors in head and neck squamous cell carcinoma (HNSCC). Promoter methylation status and gene expression were assessed in a large panel of head and neck primary tumors, based on the hypothesis that cytosine-guanine dinucleotide (CpG) hypermethylation might silence the galanin receptor 2 (GALR2) gene.
  
  
  METHODS
  GALR2 expression was examined in a panel of cell lines by using quantitative reverse transcription polymerase chain reaction (RT-PCR). The methylation status of the GALR2 promoter was studied using quantitative methylation-specific PCR (Q-MSP). UM-SCC-1 was stably transfected to express GALR2.
  
  
  RESULTS
  GALR2 expression was suppressed in UM-SCC cell lines, whereas nonmalignant cell lines exhibited stable expression. GALR2 methylation found in 31 of 100 (31.0%) tumor specimens was significantly correlated with the methylation status of both GALR1 and Galanin. The observed GALR2 promoter hypermethylation was statistically correlated with a decrease in disease-free survival (log-rank test, P=.045). A multivariate logistic-regression analysis revealed a high odds ratio for recurring methylation of GALR2 and the gene pair GALR2 and Galanin, 8.95 (95% confidence interval, 2.29-35.03; P=.024) and 9.05 (95% confidence interval, 1.76-46.50; P=.008), respectively. In addition, exogenous expression of GALR2 suppressed cell proliferation in UM-SCC-1 cells with hypermethylated Galanin and GALR2-proficient cell lines.
  
  
  CONCLUSIONS
  Frequent promoter hypermethylation in association with prognosis, and growth suppression after re-expression, supports the hypothesis that GALR2 may act to suppress tumor activity. GALR2 is a potentially significant therapeutic target and prognostic factor for this cancer type.
authors.affiliation: Department of Otolaryngology/Head and Neck Surgery, Hamamatsu University School of Medicine, Shizuoka, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Misawa
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Misawa
authors.forename: Takeharu
authors.initials: T
authors.lastname: Kanazawa
authors.forename: Takayuki
authors.initials: T
authors.lastname: Uehara
authors.forename: Shori
authors.initials: S
authors.lastname: Endo
authors.forename: Daiki
authors.initials: D
authors.lastname: Mochizuki
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamatodani
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Carey
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Mineta
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000401:mortality / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D018899:CpG Islands; D019175:DNA Methylation; D018572:Disease-Free Survival; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D016147:Genes, Tumor Suppressor; D006258:Head and Neck Neoplasms / Q000235:genetics* / Q000401:mortality / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011401:Promoter Regions, Genetic; D044091:Receptor, Galanin, Type 1 / Q000235:genetics; D044092:Receptor, Galanin, Type 2 / Q000235:genetics* / Q000378:metabolism; D000077195:Squamous Cell Carcinoma of Head and Neck
chemical_list: D044091:Receptor, Galanin, Type 1; D044092:Receptor, Galanin, Type 2
keywords: GALR1; GALR2; Galanin; cytosine-guanine dinucleotide islands; head and neck cancer; hypermethylation