Abstract A029: Identification of tumor microenvironment components in patient-derived pancreatic ductal adenocarcinoma organoids

Abstract

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) is highly drug resistant with no change in therapeutic approach for the last decade. The PDAC tumor microenvironment (TME) is highly desmoplastic and associated with altered treatment response. Our group previously identified 9 distinct cell types in human PDAC tumors using single-cell RNA-sequencing, demonstrating a diverse TME. However, the TME of in vitro organoid PDAC models remains underexplored. We initiated characterization of the TME from PDAC patient derived organoids (PDOs) to establish a working model for accurate drug sensitivity testing. Methods: We performed immunofluorescence (IF) staining on whole-mount early passage (<P4) PDO lines and corresponding paraffin-embedded primary PDAC specimens to evaluate for activated cancer-associated fibroblasts (CAFs) using antibodies against α-smooth muscle actin (α-SMA) and fibroblast activated protein (FAP); and to evaluate for T-regulatory (Treg) cells with antibodies against interleukin-2 receptor α (IL-2Rα) and forkhead box protein P3 (FOXP3). Results: CAFs promote an immunosuppressive TME in PDAC and have recently been subclassified into inflammatory fibroblasts and myofibroblasts, which can both restrain and promote tumor progression. In this study, we identified three distinct subtypes of CAFs in PDOs, which are consistent with the subtypes found in matched clinical tumor specimens: α-SMA+, which has been reported to be indicative of pancreatic stellate cell activation and associated with increased desmoplasia; FAP+, which influences cancer cell motility, invasion, and cycle progression, extracellular matrix deposition, and angiogenesis within the TME; and α-SMA+/FAP+, which is a myofibroblast subtype. We additionally identified Treg populations in PDOs with peripheral IL-2Rα and central FOXP3 expression in the organoid spheres. Tregs have previously been shown to be overexpressed in the PDAC TME, making this finding clinically relevant. Conclusions: In this preliminary study, we show that PDAC PDOs demonstrate TME components that mirror primary tumor specimens, including CAFs and Tregs. The demonstration of a tumor-matched, immunocompetent TME in PDAC PDOs provides a more clinically relevant in vitro tumor model for patient-matched drug sensitivity testing. Citation Format: Mei Gao, Charles J. Bailey, Megan M. Harper, Michael J. Cavnar, Prakash Pandalai, Shadi A. Qasem, Joseph Kim. Identification of tumor microenvironment components in patient-derived pancreatic ductal adenocarcinoma organoids [abstract]. In: Proceedings of the AACR Special Conference on the Evolutionary Dynamics in Carcinogenesis and Response to Therapy; 2022 Mar 14-17. Philadelphia (PA): AACR; Cancer Res 2022;82(10 Suppl):Abstract nr A029.