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Bromo and extra terminal (BET) proteins (BRD2, BRD3, BRD4, and BRDT) are transcriptional regulators required for efficient expression of several growth promoting and antiapoptotic genes as well as for cell-cycle progression. BET proteins are recruited on transcriptionally active chromatin via their two N-terminal bromodomains (BRD), a protein interaction module that specifically recognizes acetylated lysine residues in histones H3 and H4. Inhibition of the BET-histone interaction results in transcriptional downregulation of a number of oncogenes, providing a novel pharmacologic strategy for the treatment of cancer. Here, we present a potent and highly selective dihydroquinazoline-2-one inhibitor, PFI-1, which efficiently blocks the interaction of BET BRDs with acetylated histone tails. Cocrystal structures showed that PFI-1 acts as an acetyl-lysine (Kac) mimetic inhibitor efficiently occupying the Kac binding site in BRD4 and BRD2. PFI-1 has antiproliferative effects on leukemic cell lines and efficiently abrogates their clonogenic growth. Exposure of sensitive cell lines with PFI-1 results in G1 cell-cycle arrest, downregulation of MYC expression, as well as induction of apoptosis and induces differentiation of primary leukemic blasts. Intriguingly, cells exposed to PFI-1 showed significant downregulation of Aurora B kinase, thus attenuating phosphorylation of the Aurora substrate H3S10, providing an alternative strategy for the specific inhibition of this well-established oncology target.

Original publication

DOI

10.1158/0008-5472.can-12-3292

Type

Journal article

Journal

Cancer research

Publication Date

06/2013

Volume

73

Pages

3336 - 3346

Addresses

Structural Genomics Consortium and Target Discovery Institute, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, USA.

Keywords

Animals, Mice, Inbred NOD, Humans, Mice, Quinazolines, Nuclear Proteins, Transcription Factors, Xenograft Model Antitumor Assays, Protein Interaction Mapping, Apoptosis, Cell Growth Processes, Down-Regulation, Protein Structure, Tertiary, Structure-Activity Relationship, Phosphorylation, Models, Molecular, Child, Precursor B-Cell Lymphoblastic Leukemia-Lymphoma, Molecular Targeted Therapy