Abstract C049: WT1+ cancer-associated fibroblasts promote pancreatic cancer growth

Abstract

Abstract Pancreatic ductal adenocarcinoma (PDA) is characterized by dense, fibro-inflammatory stroma that is established in early pathogenesis. Cancer-associated fibroblasts (CAFs) make up a significant proportion of the tumor microenvironment and represent a heterogeneous cell population that play both tumor-promoting and tumor-restricting roles. Despite their dramatic expansion in PDA pathogenesis, it is still unclear what cells in the normal pancreas give rise to these CAFs. Lineage-tracing experiments have previously identified pancreatic stellate cells, mesothelial, and tissue-resident fibroblasts as progenitors to subsets of CAFs. In this research, we firstly pulse-labeled cells expressing the mesothelial and fibroblast marker Wilms tumor 1 (WT1) in the normal pancreas of WT1CreERT;R26tdTomato mice and used an orthotopic model of PDA to trace their contribution to the PDA tumor microenvironment. We found WT1+ cells in the normal pancreas expanded to comprise a significant proportion of PDA CAFs according to immunofluorescence. Based upon single-cell RNA-sequencing (scRNA-seq), these WT1+ precursors represent an endogenous pancreatic fibroblast population similar to previously characterized universal adventitial fibroblasts (Pi16+, Dpp4+). To determine the role of WT1 in established PDA, we labeled WT1+ cells following orthotopic tumor implantation into WT1CreERT;R26tdTomato mice, and scRNA-seq analysis revealed that both inflammatory CAFs (iCAFs) and myofibroblastic CAFs (MyCAFs) express WT1. Notably, iCAFs had higher relative expression of WT1+. Additionally, we depleted WT1+ cells with diphtheria toxin from orthotopic tumors established in WT1CreERT;R26tdTomato/iDTR mice. We found depletion of WT1+ cells reduced orthotopic tumor growth, and depleted fibroblasts from the PDA tumor microenvironment. These findings implicate WT1 as a promising lineage tracing marker for a subset of pancreatic fibroblasts and demonstrates a pro-tumorigenic role of WT1+ fibroblasts in PDA. Citation Format: Allison Bischoff, Yaqing Zhang, Wei Yan, Kristee Brown, Wenting Du, Marina Pasca di Magliano. WT1+ cancer-associated fibroblasts promote pancreatic cancer growth [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr C049.