Abstract 2962: Molecular mechanisms underlying the sensitizing effect of mutant p53 protein expression for Auranofin treatment of NSCLC and PDAC cells
Authors: Boullosa Laurie Freire , Lardon Filip , Smits Evelien , Deben Christophe 
Published: September 2020

Abstract
Introduction: Auranofin (AF) is an orally available, organogold compound that is FDA-approved for its use in rheumatoid arthritis. AF gained interest as an anti-cancer agent since it acts as a thioredoxin reductase (TrxR) inhibitor. Data extracted from The Cancer Genome Atlas show that TXNRD1 is abundantly expressed in lung adenocarcinoma patients and negatively affects their outcome, making TrxR1 an attractable target in non-small cell lung cancer (NSCLC) patients. The goal of this study was to determine if mutant p53 expression can be used as a predictive biomarker for the treatment of AF in NSCLC. In addition, we aimed to obtain a profound understanding of the molecular mechanisms that govern the sensitizing effect of mutant p53 towards AF-treated NSCLC cells by investigating the type of cell death.
Material and methods: We determined IC50-values using the sulforhodamine-B assay for AF in a panel of NSCLC and pancreatic ductal adenocarcinoma (PDAC) cell lines with different p53 mutations and expression levels. In addition, we correlated these IC50-values to baseline expression levels of different antioxidant related proteins. Results were confirmed in the NSCLC cell line NCI-H1299 (p53 deletion, null) and its two isogenic derivates (mutant p53 R175H or R273H knock-in). mRNA-Seq of the isogenic cell line panel was performed after exposure to a medium dose of AF. Finally, the IncuCyte ZOOM system was used to determine the percentage of AF-induced cell death by the means of the Cytotox Green reagent after pretreatment of the tumor cells with a panel of apoptosis, necroptosis and ferroptosis inhibitors.
Results: A strong inverse correlation was observed between mutant p53 protein expression and AF IC50-values and baseline Trx levels in the NSCLC and PDAC cells, indicating that mutant p53 can sensitize cancer cells for AF. This sensitizing effect was confirmed in the p53Mutant isogenic NSCLC cells. Transcriptome analysis revealed the up- and downregulation of specific genes involved in ferroptosis. More specifically, AF induced cell death through various mechanisms, including apoptosis and ferroptosis, which were dependent on the expression levels of p53 rather than the type of p53 mutation. In cells with high expression levels of mutant p53, AF induced ferroptosis and lipid peroxidation. At lower expression levels of p53, the apoptosis pathway was triggered by AF with an increase in caspase-3/7 positive cells and inhibition of cell death by the caspase inhibitor Z-VAD-FMK.
Conclusion: Mutant p53 protein expression renders NSCLC and PDAC cells more susceptible to AF. In an isogenic setting, medium levels of mutant p53 sensitize NSCLC cells for apoptosis while cells with higher levels are effectively killed through ferroptosis. Altogether, AF presents a potential novel therapeutic strategy to efficiently kill p53 mutated NSCLC tumor cells by various types of cell death.
Citation Format: Laurie Freire Boullosa, Filip Lardon, Evelien Smits, Christophe Deben. Molecular mechanisms underlying the sensitizing effect of mutant p53 protein expression for Auranofin treatment of NSCLC and PDAC cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2962.