Abstract 1134: Dissecting pancreatic cancer tumor-immune microenvironment crosstalk using spatial transcriptomics

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) often fails to respond to immune therapies due to various factors, including the role of Epithelial to Mesenchymal Transition (EMT) plasticity in conferring broad resistance to diverse therapies. However, the relationship between cancer cell heterogeneity and the tumor immune microenvironment remains unclear. To address this, we utilized single cell RNA-seq and spatial transcriptomics to uncover the landscape of these cell-cell interactions in human PDAC. Here, we applied to specimens from a clinical trial testing Losartan, an indirect TGF-beta inhibitor with FOLFIRINOX chemotherapy and nivolumab (anti-PD1) in a randomized multi-institutional clinical trial for PDAC (NCT03563248). Methods: Using the NanoString GeoMx Digital Spatial Profiler, we selected multiple regions of interest in formalin-fixed paraffin-embedded (FFPE) human PDAC specimens. Immunofluorescent antibody-guided isolation of RNA and protein from cancer cells (pan-cytokeratin), cancer-associated fibroblasts (alpha-SMA), and immune cells (CD45) were performed. Utilizing the whole transcriptome assay (WTA; 18, 000+ protein-coding genes) and a new IO Proteome Atlas (IPA; 500+ plex proteins), we ventured to understand the relationship between tumor cells and the surrounding microenvironment. Results: PDAC cells, CAFs, and immune cells were successfully characterized using NanoString GeoMx in clinical trial specimens. Analysis revealed associations between cancer cell plasticity, TGF-beta signaling mesenchymal subtypes in PDAC cells. These TGF-beta enriched mesenchymal PDAC cells were enriched in Arm 1 (FOLFIRINOX) compared to Arm 2 (FOLFIRINOX+losartan). Immune deconvolution analysis identified variations in immune infiltrates, showing an anti-correlation between macrophages and T-cells. The IPA analysis revealed lower MHC I protein levels in short compared to long term survivors in Arm 3. Conclusions: Spatial transcriptomics and proteomics reveal insights into the spatial relationship between PDAC tumor cell EMT plasticity, CAFs, and immune infiltrates. This enables the discovery of novel immune response biomarkers and potential therapeutic avenues to target tumor and microenvironment interactions. Trial Registration: DF/HCC protocol 18-179: Losartan and Nivolumab in Combination With FOLFIRINOX and SBRT in Localized Pancreatic Cancer. NCT03563248 Ethics Approval: All studies presented were approved by the Dana-Farber/Harvard Cancer Center IRB protocols 18-179. Citation Format: Amaya Pankaj, Michael J. Raabe, Bidish K. Patel, Evan R. Lang, Joshua R. Kocher, Katherine H. Xu, Linda T. Nieman, William L. Hwang, Alec C. Kimmelman, David P. Ryan, Theodore S. Hong, Martin J. Aryee, David T. Ting. Dissecting pancreatic cancer tumor-immune microenvironment crosstalk using spatial transcriptomics 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 1134.