Unknown,Transcriptomics,Genomics,Proteomics

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Targeting MYCN in Neuroblastoma by BET Bromodomain Inhibition

ABSTRACT: Bromodomain inhibition comprises a promising therapeutic strategy in cancer, particularly for hematologic malignancies. To date, however, genomic biomarkers to direct clinical translation have been lacking. We conducted a cell-based screen of genetically-defined cancer cell lines using a prototypical inhibitor of BET bromodomains. Integration of genetic features with chemosensitivity data revealed a robust correlation between MYCN amplification and sensitivity to bromodomain inhibition. We characterized the mechanistic and translational significance of this finding in neuroblastoma, a childhood cancer with frequent amplification of MYCN. Genome-wide expression analysis demonstrated downregulation of the MYCN transcriptional program accompanied by suppression of MYCN transcription. Functionally, bromodomain-mediated inhibition of MYCN impaired growth and induced apoptosis in neuroblastoma. BRD4 knock-down phenocopied these effects, establishing BET bromodomains as transcriptional regulators of MYCN. BET inhibition conferred a significant survival advantage in three in vivo neuroblastoma models, providing a compelling rationale for developing BET bromodomain inhibitors in patients with neuroblastoma. Significance: Biomarkers of response to small-molecule inhibitors of BET bromodomains, a new compound class with promising anti-cancer activity, have been lacking. Here, we reveal MYCN amplification as a strong genetic predictor of sensitivity to BET bromodomain inhibitors, demonstrate a mechanistic rationale for this finding, and provide a translational framework for clinical trial development of BET bromodomain inhibitors for pediatric patients with MYCN-amplified neuroblastoma. JQ1 is a novel thieno-triazolo-1,4-diazepine, which displaces BET bromodomains from chromatin by competitively binding to the acetyl lysine recognition pocket. BE(2)-C and Kelly cells were treated in triplicate with 1 ÂµM JQ1 or DMSO for 24 hours. RNA was extracted and a decrease in MYCN transcript was confirmed by real time RT-PCR as described above. The samples were profiled using the Affymetrix PrimeView Human Gene Expression Array (Affymetrix) at Beth Israel Deaconess Medical Center (Boston, MA, USA).

ORGANISM(S): Homo sapiens

SUBMITTER: Gabriela Alexe

PROVIDER: E-GEOD-43392 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Targeting MYCN in neuroblastoma by BET bromodomain inhibition.

Puissant Alexandre A Frumm Stacey M SM Alexe Gabriela G Bassil Christopher F CF Qi Jun J Chanthery Yvan H YH Nekritz Erin A EA Zeid Rhamy R Gustafson William Clay WC Greninger Patricia P Garnett Matthew J MJ McDermott Ultan U Benes Cyril H CH Kung Andrew L AL Weiss William A WA Bradner James E JE Stegmaier Kimberly K

Cancer discovery 20130221 3

Bromodomain inhibition comprises a promising therapeutic strategy in cancer, particularly for hematologic malignancies. To date, however, genomic biomarkers to direct clinical translation have been lacking. We conducted a cell-based screen of genetically defined cancer cell lines using a prototypical inhibitor of BET bromodomains. Integration of genetic features with chemosensitivity data revealed a robust correlation between MYCN amplification and sensitivity to bromodomain inhibition. We chara ...[more]

PMID: 23430699

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Project description:Selective bromodomains inhibitors block the interaction between diverse bromodomains and extraterminal domains (BET) proteins and acetylated proteins. These inhibitors have shown beneficial effects in cancers malignancies and experimental inflammation in mouse models, but data on renal diseases are scarce. We have investigated the effect of the BET proteins inhibitor JQ1 in a mice model of unilateral ureteral obstruction. Treatment with JQ1 diminished renal damage, the presence of inflammatory cell infiltration and the upregulation of proinflammatory genes. The in vitro evaluation of JQ1 on TNF-Î± inducible genes in renal cells showed that BET inhibition modulated several biological processes, including inflammation or immune response. Moreover, gene-silencing experiments showed that BRD4 regulates several proinflammatory genes (IL-6, CCL-2 and CCL-5) and chromatin immunoprecipitation techniques demonstrated that BRD4 specifically binds to acetylated histone H3 in the promoter region of those genes. The nuclear factor-ï«B (NF-ï«B) pathway regulates renal inflammation. The RelA NF-ï«B subunit is activated by acetylation of lysine 310. In damaged kidneys and in TNF-Î±-treated renal cells, JQ1 blocked the nuclear translocation of RelA/NF-ï«B and NF-ï«B-mediated gene expression. Additionally, obstructed kidneys showed an activation of the Th17 immune response, which was diminished by JQ1 treatment. Our results demonstrate that the BET inhibition decreases renal inflammation by 3 independent mechanisms: 1) chromatin remodelling in the promoter regions of specific genes, 2) blocking NF-ï«B pathway activation, and 3) modulating the Th17 immune response. These results suggest that BET inhibitors could have important therapeutic applications in inflammatory renal diseases. HK2 cell line was treated with JQ1 or its enantiomer JQ1(-) (500nM) for 1 hour before stimulation or not with TNF-Î± (5ng/ml) for additional 3h. We analized the genes up- and down-regulated by TNF-Î± vs unstimulated cells, and further the genes downregulated or unaffected by JQ1 compared to the cells treated with the enantiomer (-) JQ1.

Dataset Information

Targeting MYCN in Neuroblastoma by BET Bromodomain Inhibition

Publications

Targeting MYCN in neuroblastoma by BET bromodomain inhibition.

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