Extensive telomere erosion is consistent with localised clonal expansions in Barrett’s metaplasia

Barrett’s oesophagus is a premalignant metaplastic condition that predisposes patients to the development of oesophageal adenocarcinoma. However, only a minor fraction of Barrett’s oesophagus patients progress to adenocarcinoma and it is thus essential to determine bio-molecular markers that can predict the progression of this condition. Telomere dysfunction is considered to drive clonal evolution in several tumour types and telomere length analysis provides clinically relevant prognostic and predictive information. The aim of this work was to use high-resolution telomere analysis to examine telomere dynamics in Barrett’s oesophagus. Telomere length analysis of XpYp, 17p, 11q and 9p, chromosome arms that contain key cancer related genes that are known to be subjected to copy number changes in Barrett’s metaplasia, revealed similar profiles at each chromosome end, indicating that no one specific telomere is likely to suffer preferential telomere erosion. Analysis of patient matched tissues (233 samples from 32 patients) sampled from normal squamous oesophagus, Z-line, and 2 cm intervals within Barrett’s metaplasia, plus oesophago-gastric junction, gastric body and antrum, revealed extensive telomere erosion in Barrett’s metaplasia to within the length ranges at which telomere fusion is detected in other tumour types. Telomere erosion was not uniform, with distinct zones displaying more extensive erosion and more homogenous telomere length profiles. These data are consistent with an extensive proliferative history of cells within Barrett’s metaplasia and are indicative of localised clonal growth. The extent of telomere erosion highlights the potential of telomere dysfunction to drive genome instability and clonal evolution in Barrett’s metaplasia

Polymorphisms of the NER pathway genes, ERCC1 and XPD are associated with esophageal adenocarcinoma risk

Purpose Functional variation in DNA repair capacity through single nucleotide polymorphisms (SNPs) of key repair genes is associated with a higher risk of developing various types of cancer. Studies have focused on the nucleotide excision repair (NER) and base excision repair (BER) pathways. We investigated whether variant alleles in seven SNPs within these pathways increased the risk of esophageal adenocarcinoma. Methods DNA was extracted from prospectively collected blood specimens. The samples were genotyped for SNPs in NER genes (XPD Lys751Gln, XPD Asp312Asn, ERCC1 8092C/A, and ERCC1 118C/T), and BER genes (XRCC1 Arg399Gln, APE1 Asp148Glu, and hOGG1 Ser326Cys). The presence of variant alleles was correlated with risk of esophageal adenocarcinoma both individually and jointly. Results Variant alleles in NER SNPs XPD Lys751Gln (AOR = 1.50, 95% CI 1.1–2.0), ERCC1 8092 C/A (AOR = 1.44, 95% CI 1.1–1.9), and ERCC1 118C/T (AOR = 1.42, 95% CI 1.0–1.9) were individually associated with esophageal adenocarcinoma risk. An increasing number of variant alleles in NER SNPs showed a significant trend with esophageal adenocarcinoma risk (p = 0.007). Conclusions The presence of variant alleles in NER genes increases risk of esophageal adenocarcinoma. There is evidence of an additive role for SNPs along a common DNA repair pathway. Future larger studies of esophageal adenocarcinoma etiology should evaluate entire biological pathways