Abstract 1270: p53-R172H mutation confers gain-of-function properties and promotes metastasis in squamous cell carcinoma
Authors: Efe Gizem , Cunningham Katherine , de Bobadilla Raul Navaridas Fernandez , Dunbar Karen J. , Sugiura Kensuke , Nishiwaki Noriyuki , Carcamo Saul , Resnick-Silverman Lois , Hasson Dan , Klein-Szanto Andres J. , Taylor Alison M. , Manfredi James J. , Prives Carol , Rustgi Anil K. 
Published: March 2024

Abstract
INTRODUCTION: Metastasis is associated with more than 90% of cancer-related mortality, and thus, there is a compelling need for innovative therapeutic breakthroughs. TP53 mutations are present in 60-70% of human cancers, especially in squamous cell cancers. For example, TP53 mutations are detected in up to 80% of esophageal squamous cell carcinomas (ESCCs). Accumulating evidence suggests that certain missense mutant forms of p53 such as R175 (R172 in mouse), R273 and R282 can acquire neomorphic pro-oncogenic activities that are referred to as gain-of-function (GOF). To elucidate novel mutant p53-dependent mechanisms in promoting metastasis, we conducted RNA-Seq, p53 ChIP-Seq and H3K27ac CUT&RUN-Seq on primary and metastatic tumor cells harvested from our mouse model of ESCC harboring Trp53R172H/−, Trp53−/− and Trp53+/+. Herein, we have identified p53-R172H gene targets in metastatic ESCC. One of the dominant effectors of p53-R172H-mediated metastasis was Colony stimulating factor-1 (Csf-1) signaling through its cognate receptor (Csf-1r), which we recently published in Cancer Discovery (PMID: 37676642). Overall, this study aims to investigate the GOF properties and mediators of mutant p53 in promoting ESCC metastasis.
RESULTS/DISCUSSION: Using ex vivo cultures and in vivo tail-vein injections, we demonstrated increased colonization and metastatic capabilities of ESCC cells harboring p53-R172H in comparison to the tumor cells with null and wild-type p53. p53-R172H occupies more genes in the metastatic ESCCs than in the primary tumors that is independent of p53 expression levels. We identified 72 unique targets of p53-R172H with altered gene occupancy and expression that occurs during the transition from primary tumor to metastasis. Such targets in metastatic ESCC are exemplified by Csf-1 and Birc5 (encoding anti-apoptosis protein Survivin) that are also enriched with H3K27ac in their promoters. They are upregulated during metastasis compared to the primary tumors dependent upon p53 mutation status, which is reinforced by TCGA data and ESCC patient-derived tissue microarrays (TMAs). Interestingly, other frequently detected “hotspot” p53 mutations including R282W and R273C, which we introduced into the ESCC cells using base editing promote differential pro-tumorigenic activities. Indeed, the analysis of SCC datasets in TCGA reveals that specific p53 mutations are associated with altered overall survival, as well as differences in the enriched pathways.
CONCLUSION: We have demonstrated GOF properties and mediators of p53-R172H in promoting ESCC metastasis that may be applicable to other SCCs. We are further expanding our analyses to additional “hotspot” p53 mutations to dissect the mechanisms of distinct p53 mutations in fostering ESCC metastasis, which can open up new avenues for therapeutic applications.
Citation Format: Gizem Efe, Katherine Cunningham, Raul Navaridas Fernandez de Bobadilla, Karen J. Dunbar, Kensuke Sugiura, Noriyuki Nishiwaki, Saul Carcamo, Lois Resnick-Silverman, Dan Hasson, Andres J. Klein-Szanto, Alison M. Taylor, James J. Manfredi, Carol Prives, Anil K. Rustgi. p53-R172H mutation confers gain-of-function properties and promotes metastasis in squamous cell carcinoma [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 1270.