title: CpG island methylation of the hTERT promoter is associated with lower telomerase activity in B-cell lymphocytic leukemia.
abstract: OBJECTIVE
  Expression of the catalytic subunit of the telomerase enzyme hTERT is essential for prolonging the replicative lifespan and is the rate-limiting step in cellular immortalization and carcinogenesis. Because hTERT expression is positively correlated with telomerase activity, its regulation is suggested as the major determinant of enzymatic activity. The hTERT promoter region contains two CpG islands, which are known to be target sites for de novo DNA methylation. To elucidate the impact of this epigenetic mechanism on telomerase activity, we analyzed the degree of hTERT promoter methylation in 30 patients with B-cell chronic lymphocytic leukemia.
  
  
  METHODS
  hTERT promoter methylation was assessed using a methylation-specific competitive polymerase chain reaction assay. The assay is based on digestion of genomic DNA with a methylation-sensitive restriction enzyme before amplification with an internal standard.
  
  
  RESULTS
  Patients exhibiting high telomerase activity showed significantly less methylation of the hTERT promoter core domain than patients with low enzyme activity. In addition, telomerase activity was significantly associated with telomere length and overall survival.
  
  
  CONCLUSIONS
  Our data show that the degree of CpG island methylation of the hTERT promoter exhibits an impact on telomerase activity in a subgroup of patients with B-cell chronic lymphocytic leukemia and therefore is assumed to play a role in regulating hTERT gene expression in these patients.
authors.affiliation: Department of General Internal Medicine, Innsbruck University Hospital, Innsbruck, Austria. Oliver.Bechter@uibk.ac.at
authors.forename: Oliver E
authors.initials: OE
authors.lastname: Bechter
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Eisterer
authors.forename: Margit
authors.initials: M
authors.lastname: Dlaska
authors.forename: Thomas
authors.initials: T
authors.lastname: Kühr
authors.forename: Josef
authors.initials: J
authors.lastname: Thaler
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D018899:CpG Islands / Q000235:genetics*; D019175:DNA Methylation; D004268:DNA-Binding Proteins; D004789:Enzyme Activation / Q000235:genetics; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D015448:Leukemia, B-Cell / Q000201:enzymology / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D011401:Promoter Regions, Genetic; D019098:Telomerase / Q000235:genetics* / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D019098:Telomerase