Disrupting the tumor-associated TNKS-USP25 protein-protein interface in cancer: structural basis, druggability, and
Emadeldin M Kamel1, Sally Mostafa Khadrawy2, Mohamed A M Ali2
1Chemistry Department, Faculty of Science, Beni-Suef University Beni-Suef 62514 Egypt drnohascience@science.bsu.edu.eg.
Abstract:
Tankyrases (TNKS1/2) are multi-domain poly(ADP-ribose) polymerases that regulate Wnt/β-catenin signaling and broader cellular programs through both catalytic activity and extensive protein-protein interaction (PPI) networks. While most tankyrase-directed drug discovery has focused on inhibiting the PARP catalytic site, an emerging alternative is to target tankyrase stability by disrupting its interaction with the deubiquitinase USP25. USP25 functions as a positive regulator of tankyrase abundance by counteracting ubiquitin-dependent turnover; consequently, blocking the TNKS-USP25 PPI can reduce tankyrase levels, stabilize pathway antagonists such as AXIN, and dampen Wnt transcriptional output. In this review, we discuss current understanding of tankyrase domain architecture with emphasis on ankyrin repeat clusters (ARC1/2/4/5) that recognize short tankyrase-binding motifs (TBMs), and we highlight why ARC5 is a particularly actionable node for intervention in the TNKS-USP25 axis. We summarize the structural basis of USP25 recruitment via a C-terminal TBM-like element, discuss ARC hotspot features that support ligandability, and provide a practical chemical-biology framework for validating PPI disruption using orthogonal assays (co-immunoprecipitation/proximity ligation, biophysics such as SPR/ITC, cellular target engagement, and displacement formats including FP/FRET). We then evaluate reported small-molecule disruptors, including C44 and UAT-B, as proof-of-concept agents that link ARC5-centered binding to tankyrase destabilization and antitumor phenotypes in prostate cancer and multidrug-resistant colorectal cancer models. Finally, we outline key challenges-selectivity across ARCs, off-target risk, and context-dependent biology-and propose future directions, including structure-guided optimization, improved cell-active chemotypes, and dual-mechanism strategies that combine PPI disruption with catalytic inhibition or targeted degradation approaches.
Insights
Targeting tankyrase (TNKS) protein-protein interactions (PPIs) with USP25 offers a novel cancer therapy. Disrupting this interaction reduces tankyrase levels, dampens Wnt signaling, and shows promise in preclinical cancer models.
Area of Science:
- Biochemistry
- Molecular Biology
- Drug Discovery
Background:
- Tankyrases (TNKS1/2) are key regulators of Wnt/β-catenin signaling via catalytic activity and protein-protein interactions (PPIs).
- Current drug discovery primarily targets TNKS catalytic sites, but disrupting TNKS stability via its interaction with USP25 presents an alternative therapeutic strategy.
- USP25 stabilizes TNKS by preventing its degradation; inhibiting this interaction reduces TNKS levels and Wnt signaling.
Purpose of the Study:
- To review the structural basis of the TNKS-USP25 interaction, focusing on the ankyrin repeat clusters (ARCs) and tankyrase-binding motifs (TBMs).
- To highlight ARC5 as a druggable target for disrupting the TNKS-USP25 axis.
- To outline a chemical-biology framework for validating PPI disruption and evaluate existing small-molecule disruptors.
Main Methods:
- Structural analysis of TNKS ankyrin repeat clusters (ARCs) and TBMs.
- Biophysical techniques (SPR, ITC) and cellular assays (co-immunoprecipitation, proximity ligation, FP/FRET) for PPI validation.
- Evaluation of small molecules (C44, UAT-B) for TNKS destabilization and phenotypic effects.
Main Results:
- ARC5 is identified as a critical and druggable node for targeting the TNKS-USP25 interaction.
- Small molecules C44 and UAT-B demonstrate proof-of-concept for disrupting the TNKS-USP25 PPI, leading to TNKS destabilization.
- Disruption of the TNKS-USP25 axis showed antitumor effects in preclinical models of prostate and colorectal cancer.
Conclusions:
- Targeting the TNKS-USP25 PPI, particularly via ARC5, offers a promising strategy for cancer therapy by destabilizing tankyrases.
- Further research should focus on structure-guided optimization, developing cell-active chemotypes, and exploring dual-mechanism approaches.
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