title: Germline epigenetic regulation of KILLIN in Cowden and Cowden-like syndrome.
abstract: BACKGROUND
  Germline loss-of-function phosphatase and tensin homolog gene (PTEN) mutations cause 80% of Cowden syndrome, a rare autosomal-dominant disorder (1 in 200,000 live births), characterized by high risks of breast, thyroid, and other cancers. A large heterogeneous group of individuals with Cowden-like syndrome, who have various combinations of Cowden syndrome features but who do not meet Cowden syndrome diagnostic criteria, have PTEN mutations less than 10% of the time, making molecular diagnosis, prediction, genetic counseling, and risk management challenging. Other mechanisms of loss of function such as hypermethylation, which should result in underexpression of PTEN or of KILLIN, a novel tumor suppressor transcribed in the opposite direction, may account for the remainder of Cowden syndrome and Cowden-like syndrome.
  
  
  OBJECTIVE
  To determine whether germline methylation is found in Cowden syndrome or Cowden-like syndrome in individuals lacking germline PTEN mutations.
  
  
  METHODS
  Nucleic acids from prospective nested series of 123 patients with Cowden syndrome or Cowden-like syndrome and 50 unaffected individuals without PTEN variants were analyzed for germline methylation and expression of PTEN and KILLIN at the Cleveland Clinic, August 2008-June 2010. Prevalence of component cancers between groups was compared using the Fisher exact test.
  
  
  METHODS
  Frequency of germline methylation in PTEN mutation-negative Cowden syndrome and Cowden syndrome-like individuals. Prevalence of component cancers in methylation-positive and PTEN mutation-positive individuals.
  
  
  RESULTS
  Of 123 patients with Cowden syndrome or Cowden-like syndrome, 45 (37%; 95% confidence interval [CI], 29%-45%) showed hypermethylation upstream of PTEN but no transcriptional repression. The germline methylation was found to transcriptionally down-regulate KILLIN by 250-fold (95% CI, 45-14 286; P = .007) and exclusively disrupted TP53 activation of KILLIN by 30% (95% CI, 7%-45%; P = .008). Demethylation treatment increased only KILLIN expression 4.88-fold (95% CI, 1.4-18.1; P = .05). Individuals with KILLIN -promoter methylation had a 3-fold increased prevalence of breast cancer (35/42 vs 24/64; P < .0001) and a greater than 2-fold increase of kidney cancer (4/45 vs 6/155; P = .004) over individuals with germline PTEN mutations.
  
  
  CONCLUSIONS
  Germline KILLIN methylation is common among patients with Cowden syndrome or Cowden-like syndrome and is associated with increased risks of breast and renal cancer over PTEN mutation-positive individuals. These observations need to be replicated.
authors.affiliation: Genomic Medicine Institute, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195, USA.
authors.forename: Kristi L
authors.initials: KL
authors.lastname: Bennett
authors.forename: Jessica
authors.initials: J
authors.lastname: Mester
authors.forename: Charis
authors.initials: C
authors.lastname: Eng
mesh_terms: D001943:Breast Neoplasms / Q000150:complications* / Q000235:genetics; D016022:Case-Control Studies; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D020868:Gene Silencing; D020022:Genetic Predisposition to Disease; D018095:Germ-Line Mutation; D006223:Hamartoma Syndrome, Multiple / Q000150:complications* / Q000235:genetics*; D006801:Humans; D051059:PTEN Phosphohydrolase / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012004:Rectal Neoplasms / Q000150:complications* / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: C554482:KLLN protein, human; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human