Driver mutations, including NPM1c, activate a BRD4-dependent core transcriptional program in Acute Myeloid Leukemia
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ABSTRACT:
ORGANISM(S): Homo sapiens
SUBMITTER: Sam Robson
PROVIDER: E-MTAB-1443 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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Project description:Bromodomain and Extra Terminal protein (BET) inhibitors are first-in-class targeted therapies that deliver a new therapeutic paradigm by directly targeting epigenetic readers1,2. Early clinical trials have shown significant promise especially in acute myeloid leukaemia (AML)3; therefore the evaluation of resistance mechanisms, an inevitable consequence of cancer therapies, is of utmost importance to optimise the clinical efficacy of these drugs. Using primary murine stem and progenitor cells immortalised with MLL-AF9, we have used an innovative approach to generate 20 cell lines derived from single cell clones demonstrating stable resistance, in vitro and in vivo, to the prototypical BET inhibitor, I-BET. Resistance to I-BET confers cross-resistance to chemically distinct BET inhibitors such as JQ1, as well as resistance to genetic knockdown of BET proteins. Resistance is not mediated through increased drug efflux or metabolism but is demonstrated to emerge from leukaemia stem cells (LSC). Resistant clones display a leukaemic granulocyte-macrophage progenitor (L-GMP) phenotype (Lin-, Sca-, cKit+, CD34+, Fc³RII/RIII+) and functionally exhibit increased clonogenic capacity in vitro and markedly shorter leukaemia latency in vivo. Chromatin bound BRD4 is globally reduced in resistant cells, however expression of key target genes such as MYC remains unaltered, highlighting the existence of alternative mechanisms to regulate transcription. We demonstrate that resistance to BET inhibitors is in part a consequence of increased Wnt/²-catenin signaling. Negative regulation of this pathway results in differentiation of resistant cells into mature leukaemic blasts, inhibition of MYC expression and restoration of sensitivity to I-BET in vitro and in vivo. Finally, we show that the sensitivity of primary human AML cells to I-BET correlates with the baseline expression of Wnt/²-catenin target genes. Together these findings provide novel insights into the biology of AML, highlight the potential therapeutic limitations of BET inhibitors and identify strategies that may overcome resistance and enhance the clinical utility of these unique targeted therapies. Comparison of iBET resistant and sensitive cell lines
2015-09-15 | E-GEOD-63682 | biostudies-arrayexpress
Project description:Bromodomain and Extra Terminal protein (BET) inhibitors are first-in-class targeted therapies that deliver a new therapeutic paradigm by directly targeting epigenetic readers1,2. Early clinical trials have shown significant promise especially in acute myeloid leukaemia (AML)3; therefore the evaluation of resistance mechanisms, an inevitable consequence of cancer therapies, is of utmost importance to optimise the clinical efficacy of these drugs. Using primary murine stem and progenitor cells immortalised with MLL-AF9, we have used an innovative approach to generate 20 cell lines derived from single cell clones demonstrating stable resistance, in vitro and in vivo, to the prototypical BET inhibitor, I-BET. Resistance to I-BET confers cross-resistance to chemically distinct BET inhibitors such as JQ1, as well as resistance to genetic knockdown of BET proteins. Resistance is not mediated through increased drug efflux or metabolism but is demonstrated to emerge from leukaemia stem cells (LSC). Resistant clones display a leukaemic granulocyte-macrophage progenitor (L-GMP) phenotype (Lin-, Sca-, cKit+, CD34+, Fc³RII/RIII+) and functionally exhibit increased clonogenic capacity in vitro and markedly shorter leukaemia latency in vivo. Chromatin bound BRD4 is globally reduced in resistant cells, however expression of key target genes such as MYC remains unaltered, highlighting the existence of alternative mechanisms to regulate transcription. We demonstrate that resistance to BET inhibitors is in part a consequence of increased Wnt/²-catenin signaling. Negative regulation of this pathway results in differentiation of resistant cells into mature leukaemic blasts, inhibition of MYC expression and restoration of sensitivity to I-BET in vitro and in vivo. Finally, we show that the sensitivity of primary human AML cells to I-BET correlates with the baseline expression of Wnt/²-catenin target genes. Together these findings provide novel insights into the biology of AML, highlight the potential therapeutic limitations of BET inhibitors and identify strategies that may overcome resistance and enhance the clinical utility of these unique targeted therapies. Comparison of iBET resistant and sensitive cell lines
2015-09-15 | E-GEOD-63681 | biostudies-arrayexpress
Project description:Bromodomain and Extra Terminal protein (BET) inhibitors are first-in-class targeted therapies that deliver a new therapeutic paradigm by directly targeting epigenetic readers. Early clinical trials have shown significant promise especially in acute myeloid leukaemia (AML)3; therefore the evaluation of resistance mechanisms, an inevitable consequence of cancer therapies, is of utmost importance to optimise the clinical efficacy of these drugs. Using primary murine stem and progenitor cells immortalised with MLL-AF9, we have used an innovative approach to generate 20 cell lines derived from single cell clones demonstrating stable resistance, in vitro and in vivo, to the prototypical BET inhibitor, I-BET. Resistance to I-BET confers cross-resistance to chemically distinct BET inhibitors such as JQ1, as well as resistance to genetic knockdown of BET proteins. Resistance is not mediated through increased drug efflux or metabolism but is demonstrated to emerge from leukaemia stem cells (LSC). Resistant clones display a leukaemic granulocyte-macrophage progenitor (L-GMP) phenotype (Lin-, Sca-, cKit+, CD34+, FcγRII/RIII+) and functionally exhibit increased clonogenic capacity in vitro and markedly shorter leukaemia latency in vivo. Chromatin bound BRD4 is globally reduced in resistant cells, however expression of key target genes such as MYC remains unaltered, highlighting the existence of alternative mechanisms to regulate transcription. We demonstrate that resistance to BET inhibitors is in part a consequence of increased Wnt/β-catenin signaling. Negative regulation of this pathway results in differentiation of resistant cells into mature leukaemic blasts, inhibition of MYC expression and restoration of sensitivity to I-BET in vitro and in vivo. Finally, we show that the sensitivity of primary human AML cells to I-BET correlates with the baseline expression of Wnt/β-catenin target genes. Together these findings provide novel insights into the biology of AML, highlight the potential therapeutic limitations of BET inhibitors and identify strategies that may overcome resistance and enhance the clinical utility of these unique targeted therapies. Total RNA obtained from iBET resistant and sensitive cells
2015-09-15 | E-GEOD-63575 | biostudies-arrayexpress
Project description:Bromodomain and extra-terminal domain (BET) family inhibitors offer a new approach to treating hematological malignancies. We used precision nuclear run-on transcription sequencing (PRO-seq) to create high-resolution maps of active RNA polymerases across the genome in t(8;21) acute myeloid leukemia (AML) that are exceptionally sensitive to BET inhibitors. PRO-seq identified over 1400 genes showing impaired release of promoter-proximal paused RNA polymerases, including the stem cell factor receptor tyrosine kinase KIT that is mutated in t(8;21) AML. PRO-seq also identified an enhancer 3â to KIT. Chromosome conformation capture confirmed contacts between this enhancer and the KIT promoter and CRISPRi-mediated repression of this enhancer impaired cell growth. PRO-seq also identified microRNAs, including MIR29C and MIR29B2 that target the anti-apoptotic factor MCL1 and were repressed by BET inhibitors. MCL1 protein was up-regulated, and inhibition of BET proteins sensitized t(8:21)-containing cells to MCL1 inhibition, suggesting a potential mechanism of resistance to BET inhibitor-induced cell death. Kasumi-1 cells were treated with DMSO, 250 nM JQ1, and 125 nM MS417 for 1 and 3 hours, and PRO-seq was performed to study transcriptional changes. Kasumi-1 cells were treated with 250 nM JQ1 for 0, 15, and 30 minutes, and PRO-seq was performed. Two biological replicates were included for each time point. Primary AML patient cells were treated with DMSO and 250 nM JQ1 for 1 hour, and PRO-seq was performed to confirm trancriptional effects of BET inhibitors.
2016-07-15 | E-GEOD-83660 | biostudies-arrayexpress
Project description:Central to the molecular pathogenesis of MLL leukaemia is the abnormal co-optation of members of transcription complexes including disrupter of telomeric silencing 1-like (DOT1L) and bromodomain containing protein 4 (BRD4). Consequently, targeted therapies against DOT1L and BRD4 are currently being evaluated in clinical trials. However, the mechanisms by which BRD4 and DOT1L regulate leukaemogenic transcription programs remain unclear. Using quantitative proteomics, chemoproteomics and biochemical fractionation we find that native BRD4 and DOT1L exist in largely separate protein complexes. Genetic disruption or small molecule inhibition of BRD4 and DOT1L shows marked synergistic activity against MLL-FP leukaemia cell lines, primary human leukaemia cells and murine leukaemia models. Mechanistically, we find a previously unrecognised functional collaboration between DOT1L and BRD4 that is especially important at highly transcribed genes in close proximity to superenhancers. DOT1L via H3K79me2 facilitates the deposition of histone H4 acetylation, which in turn regulates the binding of BRD4 to chromatin. These data provide novel insights into the regulation of transcription and specify a molecular framework for therapeutic intervention in this poor prognostic disease. ChIPSeq of MV4;11 cell treated with DMSO, I-BET, SGC0946 and combination of I-BET and SGC0946
2016-06-12 | E-GEOD-71776 | biostudies-arrayexpress
Project description:The bromodomain and extraterminal (BET) protein BRD4 is a therapeutic target in acute myeloid leukemia (AML). Here, we demonstrate that the AML maintenance function of BRD4 requires its interaction with NSD3, which belongs to a subfamily of H3K36 methyltransferases. Unexpectedly, AML cells were found to only require a short isoform of NSD3 that lacks the methyltransferase domain. We show that NSD3-short is an adaptor protein that sustains leukemia by linking BRD4 to the CHD8 chromatin remodeler, by using a PWWP chromatin reader module, and by employing an acidic transactivation domain. Genetic targeting of NSD3 or CHD8 mimics the phenotypic and transcriptional effects of BRD4 inhibition. Furthermore, BRD4, NSD3, and CHD8 colocalize across the AML genome, and each is released from super-enhancer regions upon chemical inhibition of BET bromodomains. These findings suggest that BET inhibitors exert therapeutic effects in leukemia by evicting BRD4-NSD3-CHD8 complexes from chromatin to suppress transcription. ChIP-Seq for regulatory factors of BRD4, NSD3, CHD8 and histone modification H3K36me2 in MLL-AF9 transformed acute myeloid leukemia cells (RN2)
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Project description:Small molecule inhibition of the BET family of proteins, which bind acetylated lysines within histones, has been shown to have a marked therapeutic benefit in pre-clinical models of MLL-fusion protein driven leukemias. Here, we report that I-BET151, a highly specific BET family bromodomain inhibitor, leads to growth inhibition in a human erythroleukemic (HEL) cell line as well as in erythroid precursors isolated from polycythemia vera patients. One of the genes most highly down regulated by I-BET151 was LMO2, an important oncogenic regulator of hematopoietic stem cell development and erythropoiesis. We previously reported that LMO2 transcription is dependent upon JAK2 kinase activity in HEL cells. Here, we show that the transcriptional changes induced by a JAK2 inhibitor (TG101209) and I-BET151 in HEL cells are significantly over-lapping, suggesting a common pathway of action. We generated JAK2 inhibitor resistant HEL cells and showed that these retain sensitivity to I-BET151. These data highlight I-BET151 as a potential alternative treatment against myeloproliferative neoplasms driven by constitutively active JAK2 kinase.
2013-08-20 | E-MTAB-1817 | biostudies-arrayexpress
Project description:Central to the molecular pathogenesis of MLL leukaemia is the abnormal co-optation of members of transcription complexes including disrupter of telomeric silencing 1-like (DOT1L) and bromodomain containing protein 4 (BRD4). Consequently, targeted therapies against DOT1L and BRD4 are currently being evaluated in clinical trials. However, the mechanisms by which BRD4 and DOT1L regulate leukaemogenic transcription programs remain unclear. Using quantitative proteomics, chemoproteomics and biochemical fractionation we find that native BRD4 and DOT1L exist in largely separate protein complexes. Genetic disruption or small molecule inhibition of BRD4 and DOT1L shows marked synergistic activity against MLL-FP leukaemia cell lines, primary human leukaemia cells and murine leukaemia models. Mechanistically, we find a previously unrecognised functional collaboration between DOT1L and BRD4 that is especially important at highly transcribed genes in close proximity to superenhancers. DOT1L via H3K79me2 facilitates the deposition of histone H4 acetylation, which in turn regulates the binding of BRD4 to chromatin. These data provide novel insights into the regulation of transcription and specify a molecular framework for therapeutic intervention in this poor prognostic disease. RNASeq of MV4;11 cell treated with DMSO, I-BET, SGC0946 and combination of I-BET and SGC0946 in duplicate
2016-06-12 | E-GEOD-71777 | biostudies-arrayexpress
Project description:Diffuse Large B-Cell Lymphoma (DLBCL) is a biologically heterogeneous and clinically aggressive disease. Here, we explore the role of BET bromodomain proteins in DLBCL, using integrative chemical genetics and functional epigenomics. We observe highly asymmetric loading of BRD4 at enhancers, with approximately 33% of all BRD4 localizing to enhancers at 1.6% of occupied genes. These super-enhancers prove particularly sensitive to bromodomain inhibition, explaining the selective effect of BET inhibitors on oncogenic and lineage-specific transcriptional circuits. Functional study of genes marked by super-enhancers identifies DLBCLs dependent on OCA-B and suggests a strategy for discovering unrecognized cancer dependencies. Translational studies performed on a comprehensive panel of DLBCLs establish a therapeutic rationale for evaluating BET inhibitors in this disease. ChIP-Seq for various transcription factors and histone modifications in diffuse large B-cell lymphoma cells
2013-12-10 | E-GEOD-46663 | biostudies-arrayexpress
Project description:Understanding the precise functions and relationship of BRD2 with other bromodomain and extraterminal motif (BET) proteins is central for the application of BET-specific and pan inhibitors. Here, we used acute protein degradation and quantitative genomic and proteomic approaches to investigate the primary functions of BRD2 in transcription. We report that BRD2 is required for TAF3-mediated Pol II initiation at low levels of H3K4me3-modified promoters and Pol II elongation by suppressing R-loops. Single and double depletion revealed that BRD2 and BRD3, but not BRD4, redundantly and independently function in Pol II transcription at different promoters and cooperatively occupy enhancers. Interestingly, we found that depletion of BRD2 affects the expression of different genes during differentiation processes, priming with promoter regulation in ES cells. Therefore, our results suggest complex interconnections between BRD2 and BRD3 at promoters to fine-tune Pol II initiation and elongation for control of cell state.
2024-05-22 | PXD030774 | Pride