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Small-Molecule Allosteric Inhibitors of Human Aspartate Transcarbamoylase Suppress Proliferation of Bone Osteosarcoma
Chao Wang1, Bidong Zhang1, Yingying Cong1,2
1XB20 Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, A. Deusinglaan 1, Groningen, 9700AV, The, Netherlands.
Abstract:
Aspartate transcarbamoylase (ATC) is the first committed step in de novo pyrimidine biosynthesis in eukaryotes and plants. A potent transition state analog of human ATCase (PALA) has previously been assessed in clinical trials for the treatment of cancer, but was ultimately unsuccessful. Additionally, inhibition of this pathway has been proposed to be a target to suppress cell proliferation in E. coli, the malarial parasite and tuberculosis. In this manuscript we screened a 70-member library of ATC inhibitors developed against the malarial and tubercular ATCases for inhibitors of the human ATC. Four compounds showed low nanomolar inhibition (IC50 30-120 nM) in an in vitro activity assay. These compounds significantly outperform PALA, which has a triphasic inhibition response under identical conditions, in which significant activity remains at PALA concentrations above 10 μM. Evidence for a druggable allosteric pocket in human ATC is provided by both in vitro enzyme kinetic, homology modeling and in silico docking. These compounds also suppress the proliferation of U2OS osteoblastoma cells by promoting cell cycle arrest in G0/G1 phase. This report provides the first evidence for an allosteric pocket in human ATC, which greatly enhances its druggability and demonstrates the potential of this series in cancer therapy.
Insights
New aspartate transcarbamoylase (ATC) inhibitors show promise for cancer therapy. These compounds effectively inhibit human ATC and suppress cancer cell proliferation, outperforming previous drug candidates.
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Research
Background:
- Aspartate transcarbamoylase (ATC) is crucial for de novo pyrimidine biosynthesis.
- Inhibiting ATC is a strategy to suppress cell proliferation in various organisms.
- Previous attempts using PALA for human ATCase inhibition in cancer therapy were unsuccessful.
Purpose of the Study:
- To screen a library of ATC inhibitors for activity against human ATC.
- To identify novel inhibitors with potential for cancer therapy.
- To investigate the druggability of human ATC.
Main Methods:
- Screening a 70-member inhibitor library against human ATC.
- In vitro enzyme activity assays to determine IC50 values.
- Homology modeling, in silico docking, and enzyme kinetics to characterize inhibition and identify allosteric pockets.
- Cell proliferation assays using U2OS osteoblastoma cells.
Main Results:
- Four compounds exhibited low nanomolar inhibition (30-120 nM IC50) against human ATC.
- These novel inhibitors significantly outperformed PALA, which showed limited efficacy.
- Evidence for a druggable allosteric pocket in human ATC was established.
- The identified compounds suppressed U2OS cell proliferation by inducing G0/G1 cell cycle arrest.
Conclusions:
- This study identifies potent, novel inhibitors of human ATC.
- The findings provide the first evidence of a druggable allosteric pocket in human ATC.
- These inhibitors demonstrate significant potential for development as cancer therapeutics.
