title: BRD4 associates with p53 in DNMT3A-mutated leukemia cells and is implicated in apoptosis by the bromodomain inhibitor JQ1.
abstract: The bromodomain and extra terminal (BET) family protein bromodomain containing protein 4 (BRD4) is an epigenetic regulator recently identified as a therapeutic target for several hematological cancers, notably mixed lineage leukemia-fusion acute myeloid leukemia (MLL-AML). Here, we show that the BRD4 bromodomain inhibitor JQ1 is highly active against the p53-wild-type Ontario Cancer Institute (OCI)-AML3 cell line which carries mutations in nucleophosmin (NPM1) and DNA methyltransferase 3 (DNMT3A) genes commonly associated with poor prognostic disease. We find that JQ1 causes caspase 3/7-mediated apoptosis and DNA damage response in these cells. In combination studies, we show that histone deacetylase (HDAC) inhibitors, the HDM2 inhibitor Nutlin-3, and the anthracycline daunorubicin all enhance the apoptotic response of JQ1. These compounds all induce activation of p53 suggesting that JQ1 might sensitize AML cells to p53-mediated cell death. In further experiments, we show that BRD4 associates with acetylated p53 but that this association is not inhibited by JQ1 indicating that the protein-protein interaction does not involve bromodomain binding of acetylated lysines. Instead, we propose that JQ1 acts to prevent BRD4-mediated recruitment of p53 to chromatin targets following its activation in OCI-AML3 cells resulting in cell cycle arrest and apoptosis in a c-MYC-independent manner. Our data suggest that BET bromodomain inhibition might enhance current chemotherapy strategies in AML, notably in poor-risk DNMT3A/NPM1-mutated disease.
authors.affiliation: Brighton and Sussex Medical School, University of Sussex, Brighton, East Sussex, BN1 9PS, U.K; Department of Haematology, Royal Sussex County Hospital, Brighton, East Sussex, BN2 5BE, U.K.
authors.forename: Helen Jayne Susan
authors.initials: HJ
authors.lastname: Stewart
authors.forename: Gillian Abigail
authors.initials: GA
authors.lastname: Horne
authors.forename: Sarah
authors.initials: S
authors.lastname: Bastow
authors.forename: Timothy James Telfer
authors.initials: TJ
authors.lastname: Chevassut
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001381:Azepines / Q000494:pharmacology; D020169:Caspases / Q000378:metabolism; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics*; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects; D000090205:DNA Methyltransferase 3A; D006801:Humans; D007938:Leukemia / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000090243:Nucleophosmin; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014230:Triazoles / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D000092468:Bromodomain Containing Proteins
chemical_list: D001381:Azepines; D020169:Caspases; D018797:Cell Cycle Proteins; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A; D009687:Nuclear Proteins; D000090243:Nucleophosmin; D014157:Transcription Factors; D014230:Triazoles; D016159:Tumor Suppressor Protein p53; C561695:(+)-JQ1 compound; C441289:BRD4 protein, human; D000092468:Bromodomain Containing Proteins; C000717967:DNMT3A protein, human; C000716967:NPM1 protein, human
keywords: AML; BRD4; DNMT3A; JQ1; bromodomain; p53