High-dimensional spatial analysis of murine tumor microenvironment highlights the heterogeneity of primary and metastatic pancreatic cancer immune landscape 3822

Abstract Description Pancreatic ductal adenocarcinoma (PDAC) is the 4th leading cause of cancer death in the United States as of 2024. Its tumor microenvironment (TME) contains heterogenous inflammatory and immunosuppressive areas due to varying immunophenotypes relating to immune cell infiltration and exhaustion. CD4+ T helper cells can contribute to these dynamics, but defined roles of some subsets in PDAC remain debatable. We hypothesize that effector CD4+ T cell subsets spatially influence levels of inflammation in the PDAC TME to promote tumor metastasis. To investigate these dynamics, we designed a novel sequential multiplex immunofluorescent panel for murine FFPE slides consisting of 50 markers to spatially capture immune cells with activation/exhaustion states, epithelial-to-mesenchymal phenotypes, vessel infiltration, and stromal deposition in the TME. Using FFPE slides also improves preservation of structural morphology and translation to human tumor samples. Here, we applied the panel to primary murine PDAC tumors and liver metastases compared to normal tissues, revealing heterogenous MHC-I presentation from primary tumor cells, variations in CD4+ subsets in the primary tumor, and increased lymphocyte infiltration in liver metastases, validating our panel with recent spatial and dissociative multimodal publications. Ultimately, we will apply the panel to mice deficient in specific CD4+ subsets to better elucidate the spatial role of effector T helper cells in PDAC metastases. Funding Sources Supported by UAB Hematology & Oncology Startup Fund; Hirshberg Foundation for Pancreatic Cancer Reasearch Topic Categories Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)