Abstract 1595: Persistence of fetal gene signatures along the mesenchymal lineage trajectory defines heterogeneity and function of pancreatic cancer associated fibroblasts
Authors: Han Lu , Walter Tom , Beaudet Joseph , Everett Caroline , Fang Kun , Zimmermann Michael , Mathison Angela , Urrutia Raul , Jin Victor , Leone Gustavo , Ostrowski Michael 
Published: March 2024

Abstract
In pancreatic ductal adenocarcinoma (PDAC), cancer associated fibroblasts (CAFs) play critical and complex roles in the tumor microenvironment. CAFs are also a major cell type in the desmoplastic stroma in PDAC and may account for half of the entire tumor tissue. Here we aimed to investigate the origin, diversification, and function of CAFs. We constructed a dual-DNA-recombinase mouse genetic model carrying KrasG12D/+; Trp53frt/+; Pdx1Flpo/+; Isl1creER/+; R26Tomato/+ alleles, referred to as KPFIT. The DNA recombinase FlpO directs expression of an oncogene Kras (G12D mutation) and loss of a tumor suppressor p53 in pancreatic epithelial cells, while creER recombines the Tomato reporter in the splanchnic mesenchyme and its descendants. The splanchnic mesenchyme is a layer of fetal tissue surrounding the endoderm where the pancreatic epithelium arises. This approach capitalized on the independent functions of FlpO/Frt and CreER/LoxP systems, allowing us to lineage trace Tomato labeled splanchnic progenies (via IT) in a spontaneous pancreatic cancer model (via KPF) within the same mouse. Our study identified the splanchnic mesenchyme as the fetal origin of pancreatic fibroblasts during homeostasis and tumorigenesis. Notably, the other two postulated origins, bone marrow and epithelial cells, have minimal contributions to fibroblasts. Importantly, single cell transcriptomic analysis indicated persistent and dynamic gene expressions along the pancreatic mesenchymal trajectory during development, homeostasis, precancer lesion and cancer. Intriguingly, certain splanchnic factors are expressed in only subtypes of adult pancreatic fibroblasts in temporally and spatially distinct patterns. Furthermore, we constructed mouse genetic models to delete one of the splanchnic factors, Gata6, specifically in CAFs, which resulted in increased tumor burden in the pancreas. This suggests a non-cell autonomous function of GATA6 in CAFs to restrain pancreatic cancer progression. In summary, this study delineated a continuous cell trajectory of the mesenchymal lineage in the pancreas across different life stages. Moreover, persistent gene expressions along the mesenchymal trajectory contributes to pancreatic CAF heterogeneity. Importantly, such persistence may constitute an inherent mechanism to suppress pancreatic cancer. The enhancement of this mechanism could be explored further for therapeutic benefits.
Citation Format: Lu Han, Tom Walter, Joseph Beaudet, Caroline Everett, Kun Fang, Michael Zimmermann, Angela Mathison, Raul Urrutia, Victor Jin, Gustavo Leone, Michael Ostrowski. Persistence of fetal gene signatures along the mesenchymal lineage trajectory defines heterogeneity and function of pancreatic cancer associated fibroblasts [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 1595.