Arsenic Trioxide Rescues Structural p53 Mutations through a Cryptic Allosteric Site

Area of Science:

• Oncology
• Molecular Biology
• Drug Discovery

Background:

• The TP53 gene is the most frequently mutated gene in human cancers.
• Mutations in TP53 often lead to protein inactivation, posing significant therapeutic challenges.
• Existing strategies for targeting p53 mutations are limited by diverse inactivation mechanisms and lack of druggable allosteric sites.

Purpose of the Study:

• To identify small molecules capable of rescuing structural p53 mutations.
• To elucidate the mechanism by which these molecules restore p53 function.
• To explore the therapeutic potential of identified compounds in preclinical cancer models.

Main Methods:

• Screening for cysteine-reactive small molecules that restore mutant p53 activity.
• Utilizing X-ray crystallography to determine the binding mode of arsenic trioxide (ATO) to p53 mutants.
• Assessing the functional restoration of mutant p53 in cellular assays.
• Evaluating the anti-tumor efficacy of ATO in mouse xenograft models.

Main Results:

• Arsenic trioxide (ATO) was identified as a cysteine-reactive compound that rescues structural p53 mutations.
• Crystal structures revealed a novel cryptic allosteric site in the p53 DNA-binding domain where arsenic binds to three cysteines.
• ATO binding stabilizes the p53 protein fold, enhancing thermostability and restoring transcriptional activity.
• ATO demonstrated tumor suppressor activity in cellular and in vivo preclinical models by reactivating mutant p53.

Conclusions:

• ATO can be repurposed to target p53 mutations by stabilizing the protein structure via a novel allosteric site.
• The findings provide a mechanistic basis for developing personalized cancer therapies targeting the most frequent p53 mutations.
• Further clinical investigation is warranted to stratify patients for ATO-based therapies.