PFI-1, a highly selective protein interaction inhibitor, targeting BET Bromodomains
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Sarah Picaud1, David Da Costa, Angeliki Thanasopoulou
1Structural Genomics Consortium and Target Discovery Institute, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, USA.
Abstract:
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.
Insights
A new drug, PFI-1, targets Bromo and extra terminal (BET) proteins, inhibiting cancer cell growth. PFI-1 blocks key interactions, downregulates MYC, and induces apoptosis, offering a novel cancer treatment strategy.
Area of Science:
- Biochemistry
- Molecular Biology
- Oncology
Background:
- Bromo and extra terminal (BET) proteins regulate gene expression crucial for cell growth and survival.
- BET proteins bind to acetylated histones via their bromodomains (BRD), a key interaction in transcription.
- Inhibiting BET-histone interactions offers a potential strategy for cancer therapy by downregulating oncogenes.
Purpose of the Study:
- To present PFI-1, a novel inhibitor targeting the interaction between BET bromodomains (BRD) and acetylated histone tails.
- To investigate the molecular mechanism and antiproliferative effects of PFI-1 in cancer cells.
Main Methods:
- Cocrystallography to determine the binding mode of PFI-1 to BRD2 and BRD4.
- Cell-based assays to assess antiproliferative effects, cell-cycle progression, gene expression changes (MYC), apoptosis induction, and differentiation.
- Analysis of downstream signaling pathways, including Aurora B kinase and H3S10 phosphorylation.
Main Results:
- PFI-1 acts as an acetyl-lysine (Kac) mimetic, effectively binding to the Kac site in BRD4 and BRD2.
- PFI-1 demonstrated potent antiproliferative and anti-clonogenic effects on leukemic cell lines.
- Treatment with PFI-1 induced G1 cell-cycle arrest, MYC downregulation, apoptosis, and differentiation in leukemic cells.
- PFI-1 significantly downregulated Aurora B kinase, impacting H3S10 phosphorylation.
Conclusions:
- PFI-1 is a potent and selective inhibitor of BET bromodomains (BRD).
- PFI-1 exhibits significant anticancer activity by disrupting key oncogenic pathways.
- PFI-1 represents a promising therapeutic agent for cancers driven by BET protein activity, including leukemia.
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