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Different spectra of recurrent gene mutations in subsets of chronic lymphocytic leukemia harboring stereotyped B-cell receptors
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Experimental and Clinical Oncology. Uppsala University, Science for Life Laboratory, SciLifeLab.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Experimental and Clinical Oncology. Uppsala University, Science for Life Laboratory, SciLifeLab.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Experimental and Clinical Oncology. Uppsala University, Science for Life Laboratory, SciLifeLab.
CERTH, Inst Appl Biosci, Thessaloniki, Greece..
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2016 (English)In: Haematologica, ISSN 0390-6078, E-ISSN 1592-8721, Vol. 101, no 8, 959-967 p.Article in journal (Refereed) Published
Abstract [en]

We report on markedly different frequencies of genetic lesions within subsets of chronic lymphocytic leukemia patients carrying mutated or unmutated stereotyped B-cell receptor immunoglobulins in the largest cohort (n=565) studied for this purpose. By combining data on recurrent gene mutations (BIRC3, MYD88, NOTCH1, SF3B1 and TP53) and cytogenetic aberrations, we reveal a subset-biased acquisition of gene mutations. More specifically, the frequency of NOTCH1 mutations was found to be enriched in subsets expressing unmutated immunoglobulin genes, i.e. #1, #6, #8 and #59 (22-34%), often in association with trisomy 12, and was significantly different (P<0.001) to the frequency observed in subset #2 (4%, aggressive disease, variable somatic hypermutation status) and subset #4 (1%, indolent disease, mutated immunoglobulin genes). Interestingly, subsets harboring a high frequency of NOTCH1 mutations were found to carry few (if any) SF3B1 mutations. This starkly contrasts with subsets #2 and #3 where, despite their immunogenetic differences, SF3B1 mutations occurred in 45% and 46% of cases, respectively. In addition, mutations within TP53, whilst enriched in subset #1 (16%), were rare in subsets# 2 and #8 (both 2%), despite all being clinically aggressive. All subsets were negative for MYD88 mutations, whereas BIRC3 mutations were infrequent. Collectively, this striking bias and skewed distribution of mutations and cytogenetic aberrations within specific chronic lymphocytic leukemia subsets implies that the mechanisms underlying clinical aggressiveness are not uniform, but rather support the existence of distinct genetic pathways of clonal evolution governed by a particular stereotyped B-cell receptor selecting a certain molecular lesion(s).

Place, publisher, year, edition, pages
2016. Vol. 101, no 8, 959-967 p.
National Category
Hematology
Identifiers
URN: urn:nbn:se:uu:diva-304419DOI: 10.3324/haematol.2016.141812ISI: 000381941900019PubMedID: 27198719OAI: oai:DiVA.org:uu-304419DiVA: diva2:1033145
Available from: 2016-10-05 Created: 2016-10-05 Last updated: 2017-11-30Bibliographically approved
In thesis
1. Recurrent Genetic Mutations in Lymphoid Malignancies
Open this publication in new window or tab >>Recurrent Genetic Mutations in Lymphoid Malignancies
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In recent years, the genetic landscape of B-cell derived lymphoid malignancies, including chronic lymphocytic leukemia (CLL), has been rapidly unraveled, identifying recurrent genetic mutations with potential clinical impact. Interestingly, ~30% of all CLL patients can be assigned to more homogeneous subsets based on the expression of a similar or “stereotyped” B-cell receptor (BcR). Considering that biased distribution of genetic mutations was recently indicated in specific stereotyped subsets, in paper I, we screened 565 subset cases, preferentially assigned to clinically aggressive subsets, and confirm the SF3B1 mutational bias in subset #2 (45%), but also report on similarly marked enrichment in subset #3 (46%). In contrast, NOTCH1 mutations were predominantly detected in subsets #1, #8, #59 and #99 (22-34%). This data further highlights a subset-biased acquisition of genetic mutations in the pathogenesis of at least certain subsets. Aberrant NF-κB signaling due to a deletion within the NFKBIE gene previously reported in CLL warranted extended investigation in other lymphoid malignancies. Therefore, in paper II, we screened 1460 patients with various lymphoid malignancies for NFKBIE deletions and reported enrichment in classical Hodgkin lymphoma (27%) and primary mediastinal B-cell lymphoma (PMBL) (23%). NFKBIE-deleted PMBL cases had higher rates of chemorefractoriness and inferior overall survival (OS). NFKBIE-deletion status remained an independent prognostic marker in multivariate analysis. EGR2 mutations were recently reported in advanced stage CLL patients; thus, in paper III we screened 2403 CLL patients for mutations in EGR2. An overall mutational frequency of 3.8% was reported and EGR2 mutations were associated with younger age, advanced stage and del(11q). EGR2 mutational status remained an independent marker of poor outcome in multivariate analysis, both in the screening and validation cohorts. Whole-genome sequencing (WGS) of 70 CLL cases, assigned to poor-prognostic subsets #1 and #2 and indolent subset #4, were investigated in Paper IV and revealed a similar skewing of SF3B1 mutations in subset #2 and NOTCH1 mutations in subset #1 to that reported in Paper I. Additionally, an increased frequency of the recently proposed CLL driver gene RPS15 was observed in subset #1. Finally, novel non-coding mutational biases were detected in both subset #1 and #2 that warrant further investigation.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 82 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1312
Keyword
Lymphoid malignancies, mutations, CLL, stereotypy, subsets, PMBL, NFKBIE, EGR2, whole-genome sequencing
National Category
Cancer and Oncology Hematology
Research subject
Molecular Genetics; Oncology
Identifiers
urn:nbn:se:uu:diva-314956 (URN)978-91-554-9850-4 (ISBN)
Public defence
2017-05-05, Rudbecksalen, Dag Hammarskjölds Väg 20, Uppsala, 13:15 (English)
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Available from: 2017-04-07 Created: 2017-03-13 Last updated: 2017-04-21

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