Molecular basis of USP7 inhibition by selective small-molecule inhibitors
Andrew P Turnbull1, Stephanos Ioannidis2, Wojciech W Krajewski1
1CRUK Therapeutic Discovery Laboratories, London Bioscience Innovation Centre, London NW1 0NH, UK.
Abstract:
Ubiquitination controls the stability of most cellular proteins, and its deregulation contributes to human diseases including cancer. Deubiquitinases remove ubiquitin from proteins, and their inhibition can induce the degradation of selected proteins, potentially including otherwise 'undruggable' targets. For example, the inhibition of ubiquitin-specific protease 7 (USP7) results in the degradation of the oncogenic E3 ligase MDM2, and leads to re-activation of the tumour suppressor p53 in various cancers. Here we report that two compounds, FT671 and FT827, inhibit USP7 with high affinity and specificity in vitro and within human cells. Co-crystal structures reveal that both compounds target a dynamic pocket near the catalytic centre of the auto-inhibited apo form of USP7, which differs from other USP deubiquitinases. Consistent with USP7 target engagement in cells, FT671 destabilizes USP7 substrates including MDM2, increases levels of p53, and results in the transcription of p53 target genes, induction of the tumour suppressor p21, and inhibition of tumour growth in mice.
Insights
Two new compounds, FT671 and FT827, effectively inhibit ubiquitin-specific protease 7 (USP7). This inhibition destabilizes cancer-promoting proteins, reactivates tumor suppressors like p53, and slows tumor growth.
Area of Science:
- Biochemistry
- Molecular Biology
- Oncology
Background:
- Protein ubiquitination regulates cellular protein stability, and its dysregulation is implicated in cancer.
- Deubiquitinases (DUBs) remove ubiquitin, offering therapeutic targets by degrading specific proteins, including those previously considered 'undruggable'.
- Inhibiting ubiquitin-specific protease 7 (USP7) degrades the oncogenic E3 ligase MDM2, reactivating the tumor suppressor p53 in cancers.
Purpose of the Study:
- To identify and characterize novel inhibitors of USP7.
- To elucidate the mechanism of USP7 inhibition by novel compounds.
- To evaluate the therapeutic potential of USP7 inhibition in preclinical cancer models.
Main Methods:
- In vitro and cellular assays to assess USP7 inhibition and specificity.
- Co-crystal structural analysis of USP7 in complex with inhibitors.
- Western blotting to analyze protein levels of USP7 substrates and p53.
- Analysis of p53 target gene transcription and p21 induction.
- In vivo studies evaluating tumor growth inhibition in mice.
Main Results:
- FT671 and FT827 demonstrate high-affinity and specific inhibition of USP7 in vitro and in human cells.
- Co-crystal structures reveal novel binding interactions within a dynamic pocket of USP7.
- FT671 treatment leads to MDM2 destabilization, increased p53 levels, and p53 target gene activation, including p21.
- Tumor growth was significantly inhibited in mice treated with FT671.
Conclusions:
- FT671 and FT827 are potent USP7 inhibitors with a distinct binding mode.
- USP7 inhibition effectively reactivates the p53 tumor suppressor pathway.
- USP7 inhibition represents a promising therapeutic strategy for treating USP7-dependent cancers.
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