Researchers identify synthetic lethal TYMS inhibitor effective against ATRX-deficient cells
Scientists developed a phenotype-first screening approach that identified PP12, a covalent fragment that selectively kills ATRX-deficient cells by inhibiting thymidylate synthase (TYMS). The study combines covalent fragment screening, chemoproteomics, and genetic analysis to link drug phenotypes to specific cellular targets. This work establishes a generalizable methodology for discovering synthetic lethal drug candidates in cancer cells with specific genetic deficiencies.
Researchers used a novel "phenotype-first" approach to screen approximately 500 cysteine-reactive covalent fragments in isogenic ATRX wild-type and knockout cells, identifying PP12 as a compound that preferentially kills ATRX-deficient cells. Through competitive click-chemoproteomics and integration with genome-wide CRISPR synthetic lethal datasets, the team identified thymidylate synthase (TYMS) as PP12's phenotypically relevant target. Target validation was confirmed through X-ray crystallography, competition assays with the known TYMS inhibitor 5-fluorouracil, and measurement of impaired dTMP synthesis in cells. Mechanistically, TYMS inhibition induces replication stress that is selectively cytotoxic to ATRX-deficient cells through a pathway dependent on FAM111A and SLFN11 proteins. The study establishes a generalizable workflow for linking covalent fragment phenotypes to target identification and mechanistic validation.
What's missing
The study does not discuss potential clinical translation timelines, toxicity profiles in normal cells, or whether this approach has been validated in animal models or patient-derived samples. Additionally, the paper does not address the prevalence of ATRX deficiency in human cancers or the potential patient populations that might benefit from this therapeutic approach.
What different sources said
- bioRxivCenter
Phenotype-first covalent fragment screening identifies a synthetic lethal TYMS inhibitor in ATRX-deficient cells
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