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- Cahill, Nicola, et al.
(author)
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450K-array analysis of chronic lymphocytic leukemia cells reveals global DNA methylation to be relatively stable over time and similar in resting and proliferative compartments
- 2013
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In: Leukemia. - : Springer Science and Business Media LLC. - 1476-5551 .- 0887-6924. ; 27:1, s. 150-158
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Journal article (peer-reviewed)abstract
- In chronic lymphocytic leukemia (CLL), the microenvironment influences gene expression patterns; however, knowledge is limited regarding the extent to which methylation changes with time and exposure to specific microenvironments. Using high-resolution 450K arrays, we provide the most comprehensive DNA methylation study of CLL to date, analyzing paired diagnostic/follow-up samples from IGHV-mutated/untreated and IGHV-unmutated/treated patients (n = 36) and patient-matched peripheral blood and lymph node samples (n = 20). On an unprecedented scale, we revealed 2239 differentially methylated CpG sites between IGHV-mutated and unmutated patients, with the majority of sites positioned outside annotated CpG islands. Intriguingly, CLL prognostic genes (for example, CLLU1, LPL, ZAP70 and NOTCH1), epigenetic regulator (for example, HDAC9, HDAC4 and DNMT3B), B-cell signaling (for example, IBTK) and numerous TGF-beta and NF-kappa B/TNF pathway genes were alternatively methylated between subgroups. Contrary, DNA methylation over time was deemed rather stable with few recurrent changes noted within subgroups. Although a larger number of non-recurrent changes were identified among IGHV-unmutated relative to mutated cases over time, these equated to a low global change. Similarly, few changes were identified between compartment cases. Altogether, we reveal CLL subgroups to display unique methylation profiles and unveil methylation as relatively stable over time and similar within different CLL compartments, implying aberrant methylation as an early leukemogenic event. Leukemia (2013) 27, 150-158; doi:10.1038/leu.2012.245
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| 3. |
- Cahill, Nicola, 1983-, et al.
(author)
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IGHV3-21 Gene Frequency in a Swedish Cohort of Patients With Newly Diagnosed Chronic Lymphocytic Leukemia
- 2012
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In: Clinical Lymphoma, Myeloma & Leukemia. - : Elsevier BV. - 2152-2650 .- 2152-2669. ; 12:3, s. 201-206
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Journal article (peer-reviewed)abstract
- The IGHV3-21 gene has been shown to be overrepresented in Scandinavian patients with chronic lymphocytic leukemia (CLL). By investigating a population-based cohort of 337 Swedish patients with CLL, a lower (6.5%) IGHV3-21 frequency was determined relative to our previous hospital-based studies (10.1%-12.7%), yet this frequency remained higher compared to other Western CLL cohorts (2.6%-4.1%). Furthermore, we confirmed the poor outcome for patients with IGHV3-21 to be independent of mutational and stereotypy status. Background: Scandinavian patients with CLL have shown an overrepresentation of the poor-prognostic IGHV3-21 gene. Furthermore, approximately 50% of patients with IGHV3-21 carry stereotyped B-cell receptors, which implicate antigen selection in leukemogenesis. These patients have also been reported to have shorter time to progression than patients with nonstereotyped IGHV3-21. Materials and Methods: To investigate the IGHV3-21 frequency and the clinical impact of IGHV3-21 stereotypy, 337 newly diagnosed Swedish CLL patients from a population-based cohort were analyzed. Results: Interestingly, the IGHV3-21 frequency was indeed lower (6.5%) in this indolent patient cohort than in our previous hospital-based cohort studies (10.1%-12.7%). Hence, a selection bias of more-aggressive cases rendered a higher proportion of IGHV3-21 cases in our original studies. Nevertheless, the Swedish IGHV3-21 frequency still remained higher when compared with other larger European or American studies (2.6%-4.1%). Finally, we confirmed the poor outcome for IGHV3-21 patients to be independent of mutational status and found stereotypy to have no impact on survival or time to treatment. Conclusion: The Swedish geographic bias in IGHV3-21 gene frequency was validated albeit at a lower frequency than previously reported. Moreover, no prognostic value could be attributed to IGHV3-21 stereotype status.
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| 4. |
- Cahill, Nicola, 1983-
(author)
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Molecular Genetic and DNA Methylation Profiling of Chronic Lymphocytic Leukaemia : A Focus on Divergent Prognostic Subgroups and Subsets
- 2012
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Doctoral thesis (other academic/artistic)abstract
- Advancements in prognostication have improved the subdivision of chronic lymphocytic leukaemia (CLL) into diverse prognostic subgroups. In CLL, IGHV unmutated and IGHV3-21 genes are associated with a poor-prognosis, conversely, IGHV mutated genes with a favourable outcome. The finding of multiple CLL subsets expressing ‘stereotyped’ B-cell receptors (BCRs) has suggested a role for antigen(s) in leukemogenesis. Patients belonging to certain stereotyped subsets share clinical and biological characteristics, yet limited knowledge exists regarding the genetic and epigenetic events that may influence their clinical behaviour. This thesis aimed to, further investigate Swedish IGHV3-21-utilising patients, screen for genetic and DNA-methylation events in CLL subgroups/subsets and study DNA methylation over time and within different CLL compartments. In paper I, IGHV gene sequencing of 337 CLL patients from a Swedish population-based cohort revealed a lower (6.5%) IGHV3-21 frequency relative to previous Swedish hospital-based studies (10.1-12.7%). Interestingly, this frequency remained higher compared to other Western CLL (2.6-4.1%) hospital-based cohorts. Furthermore, we confirmed the poor-outcome for IGHV3-21 patients to be independent of mutational and stereotypy status. In paper II, genomic events in stereotyped IGHV3-21-subset #2, IGHV4-34-subset #4 and subset #16 and their non-stereotyped counterparts were investigated via SNP arrays (n=101). Subset #2 and non-subset #2 carried a higher frequency of events compared to subset #4. A high frequency of del(11q) was evident in IGHV3-21 patients particularly subset #2 cases, which may partially explain their poor-prognosis. In contrast, the lower prevalence of aberrations and absence of poor-prognostic alterations may reflect the inherent low-proliferative disease seen in subset #4 cases. In papers III and IV, differential methylation profiles in IGHV mutated and IGHV unmutated patients were identified using DNA-methylation microarrays. CLL prognostic genes (CLLU1, LPL), tumor-suppressor genes (TSGs) (ABI3, WISP3) and genes belonging to TGF-ß and NF-kB/TNFR1 pathways were differentially methylated between the subgroups. Additionally, the re-expression of methylated TSGs by use of methyl and deacetyl inhibitors was demonstrated. Interestingly, analysis of patient-paired diagnostic/follow-up samples and patient-matched lymph node (LN) and peripheral blood (PB) cases revealed global DNA methylation to be relatively stable over time and remarkably similar within the different compartments. Altogether, this thesis provides insight into the aberrant genomic and DNA methylation events in divergent CLL subgroups. Moreover this thesis helps distinguish the extent to which DNA methylation changes with respect to time and microenvironment in CLL.
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| 6. |
- Gunnarsson, Rebeqa, et al.
(author)
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Array-based genomic screening at diagnosis and during follow-up in chronic lymphocytic leukemia
- 2011
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In: Haematologica. - : Ferrata Storti Foundation (Haematologica). - 1592-8721 .- 0390-6078. ; 96:8, s. 1161-1169
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Journal article (peer-reviewed)abstract
- Background High-resolution genomic microarrays enable simultaneous detection of copy-number aberrations such as the known recurrent aberrations in chronic lymphocytic leukemia [del(11q), del(13q), del(17p) and trisomy 12], and copy-number neutral loss of heterozygosity. Moreover, comparison of genomic profiles from sequential patients' samples allows detection of clonal evolution. Design and Methods We screened samples from 369 patients with newly diagnosed chronic lymphocytic leukemia from a population-based cohort using 250K single nucleotide polymorphism-arrays. Clonal evolution was evaluated in 59 follow-up samples obtained after 5-9 years. Results At diagnosis, copy-number aberrations were identified in 90% of patients; 70% carried known recurrent alterations, including del(13q) (55%), trisomy 12 (10.5%), del(11q) (10%), and del(17p) (4%). Additional recurrent aberrations were detected on chromosomes 2 (1.9%), 4 (1.4%), 8 (1.6%) and 14 (1.6%). Thirteen patients (3.5%) displayed recurrent copy-number neutral loss of heterozygosity on 13q, of whom 11 had concurrent homozygous del(13q). Genomic complexity and large 13q deletions correlated with inferior outcome, while the former was linked to poor-prognostic aberrations. In the follow-up study, clonal evolution developed in 8/24 (33%) patients with unmutated IGHV, and in 4/25 (16%) IGHV-mutated and treated patients. In contrast, untreated patients with mutated IGHV (n=10) did not acquire additional aberrations. The most common secondary event, del(13q), was detected in 6/12 (50%) of all patients with acquired alterations. Interestingly, aberrations on, for example, chromosome 6q, 8p, 9p and 10q developed exclusively in patients with unmutated IGHV. Conclusions Whole-genome screening revealed a high frequency of genomic aberrations in newly diagnosed chronic lymphocytic leukemia. Clonal evolution was associated with other markers of aggressive disease and commonly included the known recurrent aberrations.
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| 8. |
- Kaderi, Mohd Arifin, et al.
(author)
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LPL is the strongest prognostic factor in a comparative analysis of RNA-based markers in early chronic lymphocytic leukemia
- 2011
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In: Haematologica. - : Ferrata Storti Foundation (Haematologica). - 0390-6078 .- 1592-8721. ; 96:8, s. 1153-1160
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Journal article (peer-reviewed)abstract
- BACKGROUND:The expression levels of LPL, ZAP70, TCL1A, CLLU1 and MCL1 have recently been proposed as prognostic factors in chronic lymphocytic leukemia. However, few studies have systematically compared these different RNA-based markers.DESIGN AND METHODS:Using real-time quantitative PCR, we measured the mRNA expression levels of these genes in unsorted samples from 252 newly diagnosed chronic lymphocytic leukemia patients and correlated our data with established prognostic markers (for example Binet stage, CD38, IGHV gene mutational status and genomic aberrations) and clinical outcome.RESULTS:High expression levels of all RNA-based markers, except MCL1, predicted shorter overall survival and time to treatment, with LPL being the most significant. In multivariate analysis including the RNA-based markers, LPL expression was the only independent prognostic marker for overall survival and time to treatment. When studying LPL expression and the established markers, LPL expression retained its independent prognostic strength for overall survival. All of the RNA-based markers, albeit with varying ability, added prognostic information to established markers, with LPL expression giving the most significant results. Notably, high LPL expression predicted a worse outcome in good-prognosis subgroups, such as patients with mutated IGHV genes, Binet stage A, CD38 negativity or favorable cytogenetics. In particular, the combination of LPL expression and CD38 could further stratify Binet stage A patients.CONCLUSIONS:LPL expression is the strongest RNA-based prognostic marker in chronic lymphocytic leukemia that could potentially be applied to predict outcome in the clinical setting, particularly in the large group of patients with favorable prognosis.
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| 9. |
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| 10. |
- Mansouri, Larry, et al.
(author)
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Short telomere length is associated with NOTCH1/SF3B1/TP53 aberrations and poor outcome in newly diagnosed chronic lymphocytic leukemia patients
- 2013
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In: American Journal of Hematology. - : Wiley. - 0361-8609 .- 1096-8652. ; 88:8, s. 647-651
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Journal article (peer-reviewed)abstract
- Most previous studies on telomere length (TL) in chronic lymphocytic leukemia (CLL) are based on referral cohorts including a high proportion of aggressive cases. Here, the impact of TL was analyzed in a population-based cohort of newly diagnosed CLL (n=265) and in relation to other prognostic markers. Short telomeres were particularly associated with high-risk genetic markers, such as NOTCH1, SF3B1, or TP53 aberrations, and predicted a short time to treatment (TTT) and overall survival (OS) (both P<0.0001). TL was an independent prognostic factor and subdivided patients with otherwise good-prognostic features (e.g., mutated IGHV genes, favorable cytogenetics) into subgroups with different outcome. Furthermore, in follow-up samples (n=119) taken 5-8 years after diagnosis, TL correlated well with TL at diagnosis and remained unaffected by treatment. Altogether, these novel data indicate that short TL already at diagnosis is associated with poor outcome in CLL and that TL can be measured at later stages of the disease.
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