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

Telomere dysfunction and fusion during the progression of chronic lymphocytic leukemia: evidence for a telomere crisis

We performed single-molecule telomere length and telomere fusion analysis in patients at different stages of chronic lymphocytic leukaemia (CLL). Our work identified the shortest telomeres ever recorded in primary human tissue reinforcing the concept that there is significant cell division in CLL. Furthermore, we provide direct evidence that critical telomere shortening, dysfunction and fusion contribute to disease progression. The frequency of short telomeres and fusion events increased with advanced disease, but importantly these were also found in a subset of early-stage patient samples indicating that these events can precede disease progression. Sequence analysis of fusion events isolated from individuals with the shortest telomeres revealed limited numbers of repeats at the breakpoint, sub-telomeric deletion and microhomology. Array-CGH analysis of individuals displaying evidence of telomere dysfunction revealed large-scale genomic rearrangements that were concentrated in the telomeric regions; this was not observed in samples with longer telomeres. The telomere dynamics observed in CLL B-cells were indistinguishable from that observed in cells undergoing crisis in culture following abrogation of the p53 pathway. Taken together our data support the concept that telomere erosion and subsequent telomere fusion is critical in the progression of CLL, and that this paradigm may extend to other malignancies