title: Extensive telomere erosion in the initiation of colorectal adenomas and its association with chromosomal instability.
abstract: BACKGROUND
  Telomere shortening, dysfunction, and fusion may facilitate the acquisition of large-scale genomic rearrangements, driving clonal evolution and tumor progression. The relative contribution that telomere dysfunction and/or APC mutation play in the chromosome instability that occurs during colorectal tumorigenesis is not clear.
  
  
  METHODS
  We used high-resolution telomere length and fusion analysis to analyze 85 adenomatous colorectal polyps obtained from 10 patients with familial adenomatous polyposis and a panel of 50 colorectal carcinomas with patient-matched normal colonic mucosa. Telomerase activity was determined using the telomeric repeat amplification protocol. Array-CGH was used to detect large-scale genomic rearrangements. Pearson correlation and Student t test were used, and all statistical tests were two-sided.
  
  
  RESULTS
  Despite the presence of telomerase activity, we observed apparent telomere shortening in colorectal polyps that correlated with large-scale genomic rearrangements (P < .0001) but was independent of polyp size and indistinguishable from that observed in colorectal carcinomas (P = .82). We also observed apparent lengthening of telomeres in both polyps and carcinomas. The extensive differences in mean telomere length of up to 4.6kb between patient-matched normal mucosa and polyps were too large to be accounted for by replicative telomere erosion alone. Telomere fusion events were detected in both polyps and carcinomas; the mutational spectrum accompanying fusion was consistent with alternative nonhomologous end joining.
  
  
  CONCLUSIONS
  Telomere length distributions observed in colorectal polyps reflect the telomere length composition of the normal originating cells from which clonal growth was initiated. Originating cells containing both short telomeres and APC mutations may give rise to polyps that exhibit short telomeres and are prone to telomere dysfunction, driving genomic instability and progression to malignancy. J Natl Cancer Inst;2013;105:1202-1211.
authors.affiliation: Institute of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff, UK.
authors.forename: Laureline
authors.initials: L
authors.lastname: Roger
authors.forename: Rhiannon E
authors.initials: RE
authors.lastname: Jones
authors.forename: Nicole H
authors.initials: NH
authors.lastname: Heppel
authors.forename: Geraint T
authors.initials: GT
authors.lastname: Williams
authors.forename: Julian R
authors.initials: JR
authors.lastname: Sampson
authors.forename: Duncan M
authors.initials: DM
authors.lastname: Baird
mesh_terms: D011125:Adenomatous Polyposis Coli / Q000235:genetics*; D000782:Aneuploidy; D002471:Cell Transformation, Neoplastic; D043171:Chromosomal Instability; D015179:Colorectal Neoplasms / Q000235:genetics*; D055028:Comparative Genomic Hybridization; D004273:DNA, Neoplasm / Q000032:analysis / Q000302:isolation & purification; D018450:Disease Progression; D006801:Humans; D059506:Telomere Shortening; D060449:Wnt Signaling Pathway / Q000235:genetics
chemical_list: D004273:DNA, Neoplasm