| 1. |
- Kanduri, Meena, 1974, et al.
(författare)
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A key role for EZH2 in epigenetic silencing of HOX genes in mantle cell lymphoma
- 2013
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Ingår i: Epigenetics. - : Informa UK Limited. - 1559-2294 .- 1559-2308. ; 8:12, s. 1280-8
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Tidskriftsartikel (refereegranskat)abstract
- The chromatin modifier EZH2 is overexpressed and associated with inferior outcome in mantle cell lymphoma (MCL). Recently, we demonstrated preferential DNA methylation of HOX genes in MCL compared with chronic lymphocytic leukemia (CLL), despite these genes not being expressed in either entity. Since EZH2 has been shown to regulate HOX gene expression, to gain further insight into its possible role in differential silencing of HOX genes in MCL vs. CLL, we performed detailed epigenetic characterization using representative cell lines and primary samples. We observed significant overexpression of EZH2 in MCL vs. CLL. Chromatin immune precipitation (ChIP) assays revealed that EZH2 catalyzed repressive H3 lysine 27 trimethylation (H3K27me3), which was sufficient to silence HOX genes in CLL, whereas in MCL H3K27me3 is accompanied by DNA methylation for a more stable repression. More importantly, hypermethylation of the HOX genes in MCL resulted from EZH2 overexpression and subsequent recruitment of the DNA methylation machinery onto HOX gene promoters. The importance of EZH2 upregulation in this process was further underscored by siRNA transfection and EZH2 inhibitor experiments. Altogether, these observations implicate EZH2 in the long-term silencing of HOX genes in MCL, and allude to its potential as a therapeutic target with clinical impact.
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| 2. |
- Pandey, Gaurav Kumar, et al.
(författare)
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The risk-associated long noncoding RNA NBAT-1 controls neuroblastoma progression by regulating cell proliferation and neuronal differentiation.
- 2014
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Ingår i: Cancer Cell. - : Elsevier BV. - 1535-6108 .- 1878-3686. ; 26:5, s. 722-737
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Tidskriftsartikel (refereegranskat)abstract
- Neuroblastoma is an embryonal tumor of the sympathetic nervous system and the most common extracranial tumor of childhood. By sequencing transcriptomes of low- and high-risk neuroblastomas, we detected differentially expressed annotated and nonannotated long noncoding RNAs (lncRNAs). We identified a lncRNA neuroblastoma associated transcript-1 (NBAT-1) as a biomarker significantly predicting clinical outcome of neuroblastoma. CpG methylation and a high-risk neuroblastoma associated SNP on chromosome 6p22 functionally contribute to NBAT-1 differential expression. Loss of NBAT-1 increases cellular proliferation and invasion. It controls these processes via epigenetic silencing of target genes. NBAT-1 loss affects neuronal differentiation through activation of the neuronal-specific transcription factor NRSF/REST. Thus, loss of NBAT-1 contributes to aggressive neuroblastoma by increasing proliferation and impairing differentiation of neuronal precursors.
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| 3. |
- Cahill, Nicola, et al.
(författare)
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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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Ingår i: Leukemia. - : Springer Science and Business Media LLC. - 1476-5551 .- 0887-6924. ; 27:1, s. 150-158
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Deneberg, Stefan, et al.
(författare)
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microRNA-34b/c on chromosome 11q23 is aberrantly methylated in chronic lymphocytic leukemia
- 2014
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Ingår i: Epigenetics. - : Informa UK Limited. - 1559-2294 .- 1559-2308. ; 9:6, s. 910-917
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Tidskriftsartikel (refereegranskat)abstract
- A commonly deleted region in chronic lymphocytic leukemia (CLL) is the 11q22-23 region, which encompasses the ATM gene. Evidence suggests that tumor suppressor genes other than ATM are likely to be involved in CLL with del(11q). A microRNA (miR) cluster including the miR-34b and miR-34c genes is located, among other genes, within the commonly deleted region (CDR) at 11q. Interestingly, these miRs are part of the TP53 network and have been shown to be epigenetically regulated. In this study, we investigated the expression and methylation status of these miRs in a well-characterized cohort of CLL, including cases with/without 11q-deletion. We show that the miR-34b/c promoter was aberrantly hypermethylated in a large proportion of CLL cases (48%, 25/52 cases). miR-34b/c expression correlated inversely to DNA methylation (P = 0.003), and presence of high H3K37me3 further suppressed expression regardless of methylation status. Furthermore, increased miR-34b/c methylation inversely correlated with the presence of 11q-deletion, indicating that methylation and del(11q) independently silence these miRs. Finally, 5-azacytidine and trichostatin A exposure synergistically increased the expression of miR-34b/c in CLL cells, and transfection of miR-34b or miR-34c into HG3 CLL cells significantly increased apoptosis. Altogether, our novel data suggest that miR-34b/c is a candidate tumor suppressor that is epigenetically silenced in CLL.
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| 5. |
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| 6. |
- Halldorsdottir, Anna Margret, et al.
(författare)
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Mantle cell lymphoma displays a homogenous methylation profile : A comparative analysis with chronic lymphocytic leukemia
- 2012
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Ingår i: American Journal of Hematology. - : John Wiley & Sons. - 0361-8609 .- 1096-8652. ; 87:4, s. 361-367
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Tidskriftsartikel (refereegranskat)abstract
- Mantle cell lymphoma (MCL) and chronic lymphocytic leukemia (CLL) are mature CD5(+) B-cell malignancies with different biological/clinical characteristics. We recently reported an association between different prognostic subgroups of CLL (i.e., IGHV mutated and unmutated) and genomic methylation pattern. However, the relationship between DNA methylation and prognostic markers, such as the proliferation gene expression signature, has not been investigated in MCL. We applied high-resolution methylation microarrays (27,578 CpG sites) to assess the global DNA methylation profiles in 20 MCL (10 each with high/low proliferation signature) and 30 CLL (15 poor-prognostic IGHV unmutated subset #1 and 15 good-prognostic IGHV mutated subset #4) samples. Notably, MCL and each CLL subset displayed distinct genomic methylation profiles. After unsupervised hierarchical clustering, 17/20 MCL cases formed a cluster separate from CLL, while CLL subsets #1 and #4 formed subclusters. Surprisingly, few differentially methylated genes (n = 6) were identified between high vs. low proliferation MCL. In contrast, distinct methylation profiles were demonstrated for MCL and CLL. Importantly, certain functional classes of genes were preferentially methylated in either disease. For instance, developmental genes, in particular homeobox transcription factor genes (e.g., HLXB9, HOXA13), were more highly methylated in MCL, whereas apoptosis-related genes were enriched among targets methylated in CLL (e.g., CYFIP2, NR4A1). Results were validated using pyrosequencing, RQ-PCR and reexpression of specific genes. In summary, the methylation profile of MCL was homogeneous and no correlation with the proliferation signature was observed. Compared to CLL, however, marked differences were discovered such as the preferential methylation of homeobox genes in MCL.
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| 7. |
- Halldorsdottir, Anna Margret, et al.
(författare)
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Mantle cell lymphoma displays a homogenous methylation profile: A comparative analysis with chronic lymphocytic leukemia
- 2012
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Ingår i: American Journal of Hematology. - : Wiley. - 0361-8609 .- 1096-8652. ; 87:4, s. 361-367
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Tidskriftsartikel (refereegranskat)abstract
- Mantle cell lymphoma (MCL) and chronic lymphocytic leukemia (CLL) are mature CD5(+) B-cell malignancies with different biological/clinical characteristics. We recently reported an association between different prognostic subgroups of CLL (i.e., IGHV mutated and unmutated) and genomic methylation pattern. However, the relationship between DNA methylation and prognostic markers, such as the proliferation gene expression signature, has not been investigated in MCL. We applied high-resolution methylation microarrays (27,578 CpG sites) to assess the global DNA methylation profiles in 20 MCL (10 each with high/low proliferation signature) and 30 CLL (15 poor-prognostic IGHV unmutated subset #1 and 15 good-prognostic IGHV mutated subset #4) samples. Notably, MCL and each CLL subset displayed distinct genomic methylation profiles. After unsupervised hierarchical clustering, 17/20 MCL cases formed a cluster separate from CLL, while CLL subsets #1 and #4 formed subclusters. Surprisingly, few differentially methylated genes (n = 6) were identified between high vs. low proliferation MCL. In contrast, distinct methylation profiles were demonstrated for MCL and CLL. Importantly, certain functional classes of genes were preferentially methylated in either disease. For instance, developmental genes, in particular homeobox transcription factor genes (e.g., HLXB9, HOXA13), were more highly methylated in MCL, whereas apoptosis-related genes were enriched among targets methylated in CLL (e.g., CYFIP2, NR4A1). Results were validated using pyrosequencing, RQ-PCR and reexpression of specific genes. In summary, the methylation profile of MCL was homogeneous and no correlation with the proliferation signature was observed. Compared to CLL, however, marked differences were discovered such as the preferential methylation of homeobox genes in MCL. Am. J. Hematol., 2012. (C) 2012 Wiley Periodicals, Inc.
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| 8. |
- Kaderi, Mohd Arifin, et al.
(författare)
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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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Ingår i: Haematologica. - : Ferrata Storti Foundation (Haematologica). - 0390-6078 .- 1592-8721. ; 96:8, s. 1153-1160
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Tidskriftsartikel (refereegranskat)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. |
- Kanduri, Meena, et al.
(författare)
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Differential genome-wide array-based methylation profiles in prognostic subsets of chronic lymphocytic leukemia
- 2010
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 115:2, s. 296-305
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Tidskriftsartikel (refereegranskat)abstract
- Global hypomethylation and regional hypermethylation are well-known epigenetic features of cancer; however, in chronic lymphocytic leukemia (CLL), studies on genome-wide epigenetic modifications are limited. Here, we analyzed the global methylation profiles in CLL, by applying high-resolution methylation microarrays (27,578 CpG sites) to 23 CLL samples, belonging to the immunoglobulin heavy-chain variable (IGHV) mutated (favorable) and IGHV unmutated/IGHV3-21 (poor-prognostic) subsets. Overall, results demonstrated significant differences in methylation patterns between these subgroups. Specifically, in IGHV unmutated CLL, we identified methylation of 7 known or candidate tumor suppressor genes (eg, VHL, ABI3, and IGSF4) as well as 8 unmethylated genes involved in cell proliferation and tumor progression (eg, ADORA3 and PRF1 enhancing the nuclear factor-kappaB and mitogen-activated protein kinase pathways, respectively). In contrast, these latter genes were silenced by methylation in IGHV mutated patients. The array data were validated for selected genes using methylation-specific polymerase chain reaction, quantitative reverse transcriptase-polymerase chain reaction, and bisulfite sequencing. Finally, the significance of DNA methylation in regulating gene promoters was shown by reinducing 4 methylated tumor suppressor genes (eg, VHL and ABI3) in IGHV unmutated samples using the methyl-inhibitor 5-aza-2'-deoxycytidine. Taken together, our data for the first time reveal differences in global methylation profiles between prognostic subsets of CLL, which may unfold epigenetic silencing mechanisms involved in CLL pathogenesis.
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| 10. |
- Kanduri, Meena, 1974, et al.
(författare)
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Distinct transcriptional control in major immunogenetic subsets of chronic lymphocytic leukemia exhibiting subset-biased global DNA methylation profiles.
- 2012
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Ingår i: Epigenetics. - : Informa UK Limited. - 1559-2294 .- 1559-2308. ; 7:12, s. 1435-42
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Tidskriftsartikel (refereegranskat)abstract
- Chronic lymphocytic leukemia (CLL) can be divided into prognostic subgroups based on the IGHV gene mutational status, and is further characterized by multiple subsets of cases with quasi-identical or stereotyped B cell receptors that also share clinical and biological features. We recently reported differential DNA methylation profiles in IGHV-mutated and IGHV-unmutated CLL subgroups. For the first time, we here explore the global methylation profiles of stereotyped subsets with different prognosis, by applying high-resolution methylation arrays on CLL samples from three major stereotyped subsets: the poor-prognostic subsets #1 (n = 15) and #2 (n = 9) and the favorable-prognostic subset #4 (n = 15). Overall, the three subsets exhibited significantly different methylation profiles, which only partially overlapped with those observed in our previous study according to IGHV gene mutational status. Specifically, gene ontology analysis of the differentially methylated genes revealed a clear enrichment of genes involved in immune response, such as B cell activation (e.g., CD80, CD86 and IL10), with higher methylation levels in subset #1 than subsets #2 and #4. Accordingly, higher expression of the co-stimulatory molecules CD80 and CD86 was demonstrated in subset #4 vs. subset #1, pointing to a key role for these molecules in the crosstalk of CLL subset #4 cells with the microenvironment. In summary, investigation of three prototypic, stereotyped CLL subsets revealed distinct DNA methylation profiles for each subset, which suggests subset-biased patterns of transcriptional control and highlights a key role for epigenetics during leukemogenesis.
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