Abstract 5553: Glycan CA19-9 mediated immune modulation in the pancreatic tumor microenvironment

Abstract Pancreatic ductal adenocarcinoma (PDA) is an intractable common malignancy with a pro-tumorigenic and immunosuppressive microenvironment (ME) that often limits treatment efficacy. Only 10-15% of patients are eligible for surgical resection, which is the only cure for PDA. The glycan CA19-9 is used to follow treatment response in PDA patients, but its functional role in PDA remained unknown until recently because rodents lack the ability to produce this carbohydrate. CA19-9 elevation in a KRAS-mutant background results in increased tumor proliferation and ME remodeling in mice. The tumor ME is encompassed by hypovascularized stroma consisting of cancer associated fibroblasts (CAFs) and tumor associated macrophages (TAMs) that contribute to desmoplasia and immunosuppression. All prior work investigating the tumor ME in PDA mouse models was performed in CA19-9 negative context, potentially missing a key element of PDA biology. Elevation of CA19-9 in mice caused expansion of both antigen-presenting (ap) CAFs and TAMs. CA19-9 induction in KRAS-mutant organoids increased gene expression of M-CSF, IL1a, and TGFb and led to increased apCAF and TAM differentiation. This project aims to uncover the mediators of CA19-9-mediated ME remodeling. CA19-9-modified macrophage colony-stimulating factor (M-CSF) was identified via immunoprecipitation and mass spectrometry from KRAS-mutant CA19-9-inducible pancreatic organoids. CA19-9-M-CSF induced increased immunosuppressive TAM differentiation in vivo and in vitro using a novel Macrophage, Organoid, and Fibroblast (MOrF) co-culture platform. This project will identify the mechanisms by which CA19-9 directly contributes to PDA ME immune modulation and unveil essential molecular underpinnings of PDA biology that will inform effective therapies in the future. Citation Format: Jasper Hsu, Tae Gyu Oh, Kristina L. Peck, Angelica E. Rock, Garret Bishop, Shira R. Okhovat, Susan M. Kaech, Dannielle D. Engle. Glycan CA19-9 mediated immune modulation in the pancreatic tumor microenvironment 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 (6Suppl): Abstract nr 5553.