Abstract B110: High-dimensional spatial analysis of murine PDAC microenvironment emphasizes primary and metastatic immune heterogeneity

Abstract Heterogeneity within the pancreatic ductal adenocarcinoma (PDAC) tumor microenvironment (TME), across tumor locations, and between patients largely contributes to poor treatment response and PDAC’s status as the fourth leading cause of cancer death in the United States. In order to identify suitable targets for innovative therapeutic interventions, it is necessary to understand and mechanistically test TME constituents, their infiltration, and their interaction dynamics in the context of primary and metastatic tumor locations using pre-clinical modeling. Therefore, we designed a novel 46-marker multiplex immunofluorescent staining panel for murine formalin-fixed paraffin-embedded (FFPE) tissues. This panel enables the spatial quantification of immune cell populations and activation/exhaustion states, epithelial-to-mesenchymal phenotypes, cancer-associated fibroblast heterogeneity, hematologic and lymphatic vessel infiltration, neuronal infiltration, and extracellular matrix deposition in the TME. We quantified the composition and spatial infiltration of the TME on matched murine primary and liver tumor samples from tandem orthotopic and hemi-spleen transplants of three distinct primary murine PDAC cell lines derived from the KPC model (KrasG12D; TP53R172H; PDX1-Cre; RosaEYFP). The resulting primary tumors from each cell line showed inter-tumoral heterogeneity as their distinct levels of immune infiltration had varying clustering patterns. Spatial analysis further revealed heterogeneous cancer cell MHC-I expression, immune cell exhaustion, and myeloid and lymphoid populations correlating with cell line. However, all liver nodules were encased by a barrier of immune cells separating the tumor from normal liver parenchyma irrespective of cell line. This observation reflects our recent spatial transcriptomic analysis of patient-derived matched liver and primary tumors, supporting the use of these pre-clinical models for future mechanistic investigations. Altogether, these data highlight the complexity of PDAC TMEs and the site-specific differences between primary and metastatic tumor composition. Citation Format: Christina R. Larson, Satwik Acharyya, Jace Baines, Ayushi Mandloi, Robert Welner, Julienne L. Carstens. High-dimensional spatial analysis of murine PDAC microenvironment emphasizes primary and metastatic immune heterogeneity abstract. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research—Emerging Science Driving Transformative Solutions; Boston, MA; 2025 Sep 28-Oct 1; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2025;85 (18Suppl₃): Abstract nr B110.