Abstract 631: Functional genetics of APR-246 rescuable TP53 mutants

Abstract

Abstract TP53, often referred to as the guardian of the genome, encodes for the p53 tumor suppressor protein, and is one of the most frequently mutated genes in human cancers. Some cancer sub-types, such as non-small cell lung carcinoma (NSCLC) and high grade serous carcinoma (HGSC), have high TP53 mutation rates reaching up to 56% and 96%, respectively. Given its multi-faceted role in human cancers, there have been several emerging therapeutic approaches targeting mutant p53. APR-246 is a small molecule drug currently in clinical trials for the functional rescue of p53 missense mutants, the most common type of p53 mutant protein, across various cancer types. APR-246 is proposed to bind mutant p53 and promote thermodynamic stabilization of the protein allowing it to regain wild-type-like conformation and consequentially regain WT-like functionality. However, there has yet to be a functional genomic screening of p53 mutants to systematically catalog which mutants are rescuable by APR-246. To address this critical gap, we have performed functional genetic screenings using a TP53 mutagenesis library. This pooled lentiviral library contains ~8,000 amino acid variants, spanning the entirety of the TP53 gene. Following stable transduction of this library into p53-null NSCLC and HGSOC cell lines, we performed functional screenings against sublethal doses of APR-246. Next-generation sequencing of the untreated and treated cell population allows for comparison of variant representation and determination of APR-246-sensitivity of p53 mutants. Preliminary statistical analysis of our screens has identified a pool of 117 “hit” mutants which are significantly depleted following treatment, indicative of APR-246-sensitivity. Two of these mutants, C242F and G266V, are non-functional, damaging mutations which occur in patients. Identifying p53 mutants that can be rescued by APR-246 will help identify which patients may benefit most from treatment with the drug. Citation Format: Anais Saunders, Caili Tong, Anthony N. Karnezis, Gary S. Leiserowitz, Jeremy R. Chein. Functional genetics of APR-246 rescuable TP53 mutants [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 631.