Abstract 3496: p53 mutation biases SCJ progenitor cells towards dysplasia rather than metaplasia in Barrett's esophagus
Authors: Lian Guodong , Malagola Ermanno , Zhao Junfei , Friedman Richard A. , Zamechek Leah B. , Wang Timothy C. 
Published: April 2023

Abstract
Objectives: Barrett's esophagus (BE) is a form of metaplasia that involves the aberrant differentiation of stem or progenitor cells at the squamocolumnar junction (SCJ). p53 mutation occurs early in BE cases that do progress to dysplasia or esophageal adenocarcinoma. Here, we aimed to elucidate the mechanisms by which p53 mutation promotes the early neoplastic progression of cardia progenitor cells in a mouse model of BE (L2-IL1β).
Methods: We generated the transgenic mice L2-IL1β; Cck2r-CreERT2; tdTomato; p53R172H/+ to determine the effect of p53 mutation on Cck2r+ cardia progenitor cell activity. Lineage tracing and pathological assessment were performed in combination at different time points to explore the effects of p53 mutation on development of precancerous lesions in the cardia glands. Organoids were derived from sorted Cck2r+ cardia cells with or without p53 mutation. Organoid forming capacity and growth assessment were tested to assess stemmness potential. Organoids were treated with the DNA damaging agent N-methyl-N-nitrosourea (MNU) to test the resistance of p53 mutant organoids to carcinogenic injury. Orthotopic transplantation of organoids into immunodeficient (NSG) mice was performed to study the influence of p53 mutation on growth in vivo. Single-cell RNA sequencing (scRNA-seq) analysis of precancerous lesions and bulk RNA-seq analysis of cardia organoids from BE mice were carried out to investigate the effects of p53 mutation on key regulatory pathways.
Results: Characterization of pathological progression combined with lineage tracing showed that over time, most p53 mutant cells did not undergo metaplasia but progressed to dysplasia in the cardia glands of IL1β mice. This suggests that the dysplastic cells likely arose directly from stem or progenitor cells rather than progressing first through metaplasia, a finding consistent with the scRNA-seq analysis. In vitro, p53 mutation increased the number and size of organoids derived from Cck2r+ progenitor cells from IL1β mice, suggesting an expansion of stem or progenitor cells. Furthermore, p53 mutation led to increased resistance of these organoids to MNU. Orthotopic transplantation experiments demonstrated that p53 mutation increased survival and proliferation of organoids in the stroma of immunodeficient murine stomach. Moreover, p53 mutant transplanted organoids retained dysplastic features with little to no metaplastic events relative to their WT counterparts. Computational analyses suggested that these heterotypic gains function in vivo and in vitro are relate to their inhibitory effect of stem cell differentiation through Notch signaling activation.
Conclusion: These findings suggest that p53R172H/+ mutation in SCJ progenitor cells directly promotes their progression toward dysplasia, rather than differentiating into metaplasia, due in part through activation of Notch signaling to maintain stemness.
Citation Format: Guodong Lian, Ermanno Malagola, Junfei Zhao, Richard A. Friedman, Leah B. Zamechek, Timothy C. Wang. p53 mutation biases SCJ progenitor cells towards dysplasia rather than metaplasia in Barrett's esophagus [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 3496.