Evolution of genomic abnormalities during CLL disease course is associated with telomere length changes

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F65269705%3A_____%2F18%3A00068992" target="_blank" >RIV/65269705:_____/18:00068992 - isvavai.cz</a>

Alternative codes found

RIV/00216224:14740/18:00104529

Result on the web

<a href="https://library.ehaweb.org/eha/2018/stockholm/214802/helena.olbertova.evolution.of.genomic.abnormalities.during.cll.disease.course.html" target="_blank" >https://library.ehaweb.org/eha/2018/stockholm/214802/helena.olbertova.evolution.of.genomic.abnormalities.during.cll.disease.course.html</a>

DOI - Digital Object Identifier

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Result language

angličtina

Original language name

Evolution of genomic abnormalities during CLL disease course is associated with telomere length changes

Original language description

Background: Telomeres are structures protecting the ends of chromosomes, which are getting shorter with each cell division. In CLL a telomere length is considered to be stable during disease course, even despite a treatment administration. It was also shown that short telomeres predict for an early need of treatment and reduced overall survival, and associate with the unmutated status of IGHV locus and higher genomic complexity. Aims: To study telomere length in the context of genomic architecture of CLL clones and their evolution during disease course. Methods: Telomere length was measured in 198 CLL patients using established qPCR protocol. Relative telomere length (RTL) was assessed by comparing to β-globin (HBB) as a single-copy gene and Human Genomic DNA (Promega) as a reference DNA. Genes recurrently mutated in CLL were sequenced by amplicon next-generation sequencing. Following mutation frequencies were found using 5% VAF cut-off: TP53 (82/244; 33.6 %), ATM (45/233; 19.3 %), NOTCH1 (36/242; 14.9 %), SF3B1 (59/238; 24.8 %), BIRC3 (26/232; 11.2 %). In 36 patients with clonal evolution detected in relapse, samples from two (29 cases), or more than two (7 cases) timepoints were analyzed. Relative expression of hTERT telomerase subunit was assessed by reverse transcription TaqMan qPCR assay, using GAPDH as a housekeeping gene and RAMOS cell line as a positive control. Results: In the cohort of 198 CLL patients, significant associations with time to first treatment, IGHV mutation status, 11q deletion, complex karyotype and mutations in TP53 and ATM genes were found in concordance with published results. In 36 patients that manifested CLL cells&apos; clonal evolution, telomere length of the major leukemic clone was different between pre-therapy and corresponding relapse sample. This specific cohort consisted primarily of patients with therapy-driven TP53 mutation expansion (26/36; 72.2 %). Changes in other tested genes were less frequent in this subgroup, which precluded their more detailed evaluation. Thus, focusing only on the cases with TP53 evolution, we observed that telomeres in relapse became shorter, remained stable, or became longer in 12/26 (46.1 %), 8/26 (30.8 %), and 5/26 (19.2 %) of patients, respectively. Additionally, in 1/26 cases studied in three timepoints, telomeres initially lengthened and subsequently shortened following exchange of dominating TP53 mutation clone (Figure 1). Altogether, in 4/7 cases with TP53 mutation proportion change tested in &gt;2 timepoints, telomere length changed according to alteration in TP53 mutation proportion. Since the observed changes of telomere length could potentially be caused by deregulated telomerase, we tested also the hTERT gene expression in all 36 patients who underwent clonal evolution. However, only weak or null hTERT expression was detected, showing no apparent correlation with telomere length or its change. Conclusion: Although telomere length is generally considered to be stable in CLL, our findings suggest that in patients undergoing clonal evolution significant changes may occur. This telomere length evolution can be likely attributed to selective pressure of therapy favoring some clones over the others. Our observation concerns primarily an acquisition of TP53 defects, thus further investigation also in the context of other CLL-related genes is warranted.

Czech name

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Czech description

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Type

O - Miscellaneous

CEP classification

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OECD FORD branch

10606 - Microbiology

Project

Result was created during the realization of more than one project. More information in the Projects tab.

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year

2018

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů