Abstract 1090: Dominant-negative TP53 variants confer radiation resistance in endometrial cancer

Abstract

Abstract Introduction: High-grade endometrial cancers (EC) belonging to the “serous-like” cluster are known to portend a worse clinical outcome. The direct contribution of commonly identified TP53 variants on radiotherapy (RT) response has not been demonstrated in EC. Methods: To assess the impact of TP53 variants, allelic frequency, and p53/p21 signaling on radio-resistance in vitro, we utilized a high-throughput radiation assay and intron targeting CRISPR-Cas9 knockout approach in two low copy-number/TP53 wild-type EC cell lines (JHUEM1/JHUEM2). This approach facilitated TP53 cDNA complementation in a TP53-null background without significant impact from copy-number burden. The effect on radiation response was determined using high-throughput methodology and area under the curve (AUC) calculation along 5 dose-points. All experiments were carried out using 2 monoclonal isolates for each guide RNA (4 total replicates) and 2 non-targeting controls. Results: Knockout (KO) of wild-type TP53 resulted in loss of downstream p21 signaling and increased radio-resistance, demonstrating the role of p53 signaling on RT response. Complementation with five common TP53 missense variants (Y220C, R273C, R273H, R248Q, R248W) into the KO cell lines led to increased p53 accumulation without an effect on p21 signaling or RT response. Complementation into the WT cell lines, mimicking tumors with low allelic frequency/heterozygous mutations, led to abrogation of p21 signaling and increased radio-resistance, establishing their gain-of-function/dominant-negative impact. Conclusions: Our findings directly implicate TP53 status on radiotherapy response in EC, providing biologic rationale for the clinical observation that these patients may benefit from chemotherapy. Additionally, our findings demonstrate that dominant-negative variant alleles similarly impact RT response by abrogating p21 signaling. Citation Format: Aaron Petty, Arda Durmaz, Brian Yard, Jacob Scott, Roberto Vargas. Dominant-negative TP53 variants confer radiation resistance in endometrial cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1090.