RNAi screen identifies Brd4 as a therapeutic target in acute myeloid leukemia
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ABSTRACT:
PROVIDER: PRJNA141017 | ENA |
REPOSITORIES: ENA
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Project description:Epigenetic pathways regulate gene expression by controlling and interpreting chromatin modifications. Cancer cells are characterized by altered epigenetic landscapes and commonly exploit the chromatin regulatory machinery to enforce oncogenic gene expression programs. While chromatin alterations are, in principle, reversible and often amendable to drug intervention, the promise of targeting such pathways therapeutically has been hampered by our limited understanding of cancer-specific epigenetic dependencies. Here we describe a non-biased approach to probe epigenetic vulnerabilities in acute myeloid leukemia (AML) – an aggressive hematopoietic malignancy often associated with aberrant chromatin states. By screening a custom shRNA library targeting known chromatin regulators in a genetically defined AML mouse model, we identify the bromodomain-containing protein Brd4 as a critical requirement for disease maintenance. Suppression of Brd4 using shRNAs or the small-molecule inhibitor JQ1 led to robust anti-leukemic effects in vitro and in vivo, accompanied by terminal myeloid differentiation. Extensive evaluation of JQ1-sensitivity in primary human leukemia samples and in established cell lines revealed a broad activity of this compound against diverse AML subtypes. These effects are, at least in part, due to a requirement for Brd4 in maintaining Myc expression and promoting aberrant self-renewal. Together, our results indicate that Brd4 is a promising therapeutic target in AML and identify a small molecule that efficiently targets Myc. These findings also highlight the utility of RNAi screening as a discovery platform for revealing epigenetic vulnerabilities for direct pharmacologic intervention in cancer. In order to understand downstream targets of Brd4, we performed array in murine or human MLL-AF9/NrasG12D cell line under the condition that Brd4 was suppressed by using shRNAs or the small molecule inhibitor JQ1. To test the hypothesis that Myc might be an important target of Brd4, we performed arrary on murine ectopic Myc overexpression MLL-AF9/NrasG12D cell under JQ1 treatment.
2011-08-03 | E-GEOD-29799 | biostudies-arrayexpress
Project description:Epigenetic pathways regulate gene expression by controlling and interpreting chromatin modifications. Cancer cells are characterized by altered epigenetic landscapes and commonly exploit the chromatin regulatory machinery to enforce oncogenic gene expression programs. While chromatin alterations are, in principle, reversible and often amendable to drug intervention, the promise of targeting such pathways therapeutically has been hampered by our limited understanding of cancer-specific epigenetic dependencies. Here we describe a non-biased approach to probe epigenetic vulnerabilities in acute myeloid leukemia (AML) – an aggressive hematopoietic malignancy often associated with aberrant chromatin states. By screening a custom shRNA library targeting known chromatin regulators in a genetically defined AML mouse model, we identify the bromodomain-containing protein Brd4 as a critical requirement for disease maintenance. Suppression of Brd4 using shRNAs or the small-molecule inhibitor JQ1 led to robust anti-leukemic effects in vitro and in vivo, accompanied by terminal myeloid differentiation. Extensive evaluation of JQ1-sensitivity in primary human leukemia samples and in established cell lines revealed a broad activity of this compound against diverse AML subtypes. These effects are, at least in part, due to a requirement for Brd4 in maintaining Myc expression and promoting aberrant self-renewal. Together, our results indicate that Brd4 is a promising therapeutic target in AML and identify a small molecule that efficiently targets Myc. These findings also highlight the utility of RNAi screening as a discovery platform for revealing epigenetic vulnerabilities for direct pharmacologic intervention in cancer.
2011-08-04 | GSE29799 | GEO
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Project description:We performed microarray analysis of cells expressing LACZ or HOXC10 treated with MEK and BRD4 inhibition in combination for 24 hours, prior to the induction of cell death, to analyze transcriptional changes that might be mechanistic drivers of the therapeutic effect. 12 samples in triplicate, 3X LACZ + vehicle treatment, 3X HOXC10 + vehicle treatment, 3X LACZ + combo treatment, 3X HOXC10 + combo treatment
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Project description:The bromodomain and extraterminal family members are epigenetic readers and transcriptional coactivators which are critically involved in various biological processes including tumorigenesis. BRD4 has been increasingly appreciated as a key oncogene and promising anticancer target. Here, we sought to characterize the expression of BRD4 and its tumorigenic roles as well as therapeutic targeting in HNSCC. Expression of BRD4 mRNA and protein was determined by bioinformatics interrogation of public available databases, primary HNSCC samples and 4NQO-induced HNSCC animal model. The tumorigenic roles of BRD4 in HNSCC were evaluated by genetic and pharmacological approach in vitro and in vivo. Therapeutic efficiency of BRD4 targeting by JQ1 was assessed in three preclinical models including xenograft model, 4NQO-induced model and patients-derived xenograft model. Gene candidates responsible for therapeutic effects of JQ1 were identified by transcriptional profiling in HNSCC cells after JQ1 exposure. Significant upregulation of BRD4 was found in primary HNSCC samples and 4NQO-induced HNSCC model. Its overexpression associated with aggressive clinicopathological features and inferior overall and disease-free survival. BRD4 depletion by genetic silencing or pharmacological inhibition impaired cell proliferation, migration and invasion and reduced tumor growth and metastasis in vivo. Transcriptional profiling of HNSCC cells following JQ1 exposure identified hundreds of genes which might mediated its antitumor effects and enriched in cancer-relevant pathways. A novel prognostic risk score derived from JQ1-regualted genes was developed to stratify patients into subgroups with favorable or inferior prognosis. Our findings reveal that BRD4 serves as a novel oncogene driving cancer progression and a robust prognostic biomarker in HNSCC. Therapeutic targeting of BRD4 represents a potent and promising strategy against HNSCC.
2019-05-09 | GSE122522 | GEO
Project description:Genomewide T. brucei RNAi screen using proteasome inhibitor
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Project description:DNA damage activates a complex signaling network in cells that blocks cell cycle progression, recruits factors involved in DNA repair, and/or triggers programs that control senescence or programmed cell death. Alterations in chromatin structure are known to be important for the initiation and propagation of the DNA damage response, although the molecular details are unclear. We investigated the role of chromatin structure in the DNA damage response by monitoring multiple timedependent checkpoint signaling and response events with a high-content multiplex image-based RNAi screen of chromatin modifying and interacting genes. We discovered that Brd4, a double bromodomain-containing protein, functions as an endogenous inhibitor of DNA damage signaling by binding to acetylated histones at sites of open chromatin and altering chromatin accessibility. Loss of Brd4 or disruption of acetyl-lysine binding results in an increase in both the number and size of radiation-induced !H2AX nuclear foci while overexpression of a Brd4 splice isoform completely suppresses !H2AX formation, despite equivalent double strand break formation. Brd4 knock-down cells displayed altered chromatin structure, prolonged cell cycle checkpoint arrest and enhanced survival after irradiation, while overexpression of Brd4 isoform B results in enhanced radiationinduced lethality. Brd4 is the target of the t(15;19) chromosomal translocation in a rare form of cancer, NUT Midline Carcinoma. Acetyl lysine-bromodomain interactions of the Brd4-NUT fusion protein suppresses !H2AX foci in discrete nuclear compartments, rendering cells more radiosensitive, mimicking overexpression of Brd4 isoform B. NUT Midline Carcinoma is sensitive to radiotherapy, however tumor material from this rare cancer is scarce. We therefore investigated Brd4 expression in another human cancer commonly treated with radiotherapy, glioblastoma multiforme, and found that expression of Brd4 isoform B correlated specifically with treatment response to radiotherapy. These data implicate Brd4 as an endogenous insulator of DNA damage signaling through recognition of epigenetic modifications in chromatin and suggest that expression of the Brd4 in human cancer can modulate the clinical response to DNA-damaging cancer therapy. Two replicates each of U2OS cells expressing either Brd4 shRNA or a control shRNA
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