Unknown,Transcriptomics,Genomics,Proteomics

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Expression data from murine acute myeloid leukemia (AML) cells following shRNA-mediated suppression of Myb

ABSTRACT: Using an integrative approach combining a Tet-off conditional AML mouse model, global expression profiling following suppression of the driving MLL-AF9 oncogene, and a new Tet-on conditional shRNA expression system we have identified Myb as critical mediator of addiction to MLL-AF9. Suppression of Myb in established AML in vivo terminates aberrant self-renewal and triggers a terminal myeloid differentiation program that precisely phenocopies the effects of suppressing MLL-AF9. Remarkably, suppressing Myb effectively eradicates aggressive and chemotherapy resistant AML. To further investigate Myb dependent transcriptional programs involved in mediating aberrant self-renewal in leukemia, we globally surveyed gene expression changes following acute shRNA-induced suppression of Myb in an established Tet-on competent model of MLL-AF9;NrasG12D-induced AML. To enable regulatable suppression of Myb in AML, we retrovirally transduced established Tet-on competent MLL-AF9;NrasG12D induced AML cells with TRMPV-Neo vectors (Zuber et al., Nature Biotech, 2010) harboring shRNAs targeting Myb (shMyb.2572 and shMyb.2652), a control shRNA targeting Renilla Luciferase (shRen.713), or an empty miR30 cassette of the recipient cloning vector (Rec). Following drug selection, shRNA expression was induced by doxycycline treatment and total RNA was isolated from sorted shRNA expressing (Venus+/dsRed+) leukemia cells after 3 days of dox treatment, and subjected to Affymetrix microarray expression analysis. Expression profiles following expression of two independent Myb shRNAs were compared to those observed after induction in shRen.713- and Rec-expressing control samples (each in 3 biological replicates).

ORGANISM(S): Mus musculus

SUBMITTER: Johannes Zuber

PROVIDER: E-GEOD-30745 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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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.

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Expression data from murine acute myeloid leukemia (AML) cells following shRNA-mediated suppression of Myb

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