Abstract
In the activated B-cell-like (ABC) subtype of diffuse large B-cell lymphoma (DLBCL), NF-κB activity is essential for viability of the malignant cells and is sustained by constitutive activity of IκB kinase (IKK) in the cytoplasm. Here, we report an unexpected role for the bromodomain and extraterminal domain (BET) proteins BRD2 and BRD4 in maintaining oncogenic IKK activity in ABC DLBCL. IKK activity was reduced by small molecules targeting BET proteins as well as by genetic knockdown of BRD2 and BRD4 expression, thereby inhibiting downstream NF-κB-driven transcriptional programs and killing ABC DLBCL cells. Using a high-throughput platform to screen for drug-drug synergy, we observed that the BET inhibitor JQ1 combined favorably with multiple drugs targeting B-cell receptor signaling, one pathway that activates IKK in ABC DLBCL. The BTK kinase inhibitor ibrutinib, which is in clinical development for the treatment of ABC DLBCL, synergized strongly with BET inhibitors in killing ABC DLBCL cells in vitro and in a xenograft mouse model. These findings provide a mechanistic basis for the clinical development of BET protein inhibitors in ABC DLBCL, particularly in combination with other modulators of oncogenic IKK signaling.
Keywords:
cancer therapy; drug synergism.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Adenine / analogs & derivatives
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Animals
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Azepines / pharmacology
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Azepines / toxicity
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Cell Cycle Proteins
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Cell Death / drug effects
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Cell Line, Tumor
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Cell Survival
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Drug Synergism
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Humans
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I-kappa B Kinase / antagonists & inhibitors*
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I-kappa B Kinase / chemistry
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I-kappa B Kinase / metabolism
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Lymphoma, Large B-Cell, Diffuse / enzymology*
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Lymphoma, Large B-Cell, Diffuse / pathology
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Mice
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Mice, SCID
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Nuclear Proteins / antagonists & inhibitors*
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Nuclear Proteins / metabolism
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Piperidines
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Protein Kinase Inhibitors / pharmacology*
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Protein Serine-Threonine Kinases / antagonists & inhibitors*
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Protein Serine-Threonine Kinases / metabolism
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Protein Structure, Tertiary
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Pyrazoles / pharmacology
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Pyrimidines / pharmacology
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Signal Transduction / drug effects
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Transcription Factors / antagonists & inhibitors*
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Transcription Factors / metabolism
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Triazoles / pharmacology
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Triazoles / toxicity
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Xenograft Model Antitumor Assays
Substances
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(+)-JQ1 compound
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Azepines
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BRD2 protein, human
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BRD4 protein, human
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Cell Cycle Proteins
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Nuclear Proteins
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Piperidines
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Protein Kinase Inhibitors
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Pyrazoles
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Pyrimidines
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Transcription Factors
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Triazoles
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ibrutinib
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Protein Serine-Threonine Kinases
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I-kappa B Kinase
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Adenine
Associated data
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GEO/GSE58791
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SRA/SRP043524