Abstract IA001: Wired for innervation: modeling the neural niche in pancreatic ductal adenocarcinoma

Abstract

The tumor microenvironment (TME) is a major driver of pancreatic ductal adenocarcinoma (PDAC) progression and therapeutic resistance. To characterize chemotherapy-induced changes in the TME, we examined matched longitudinal tissue specimens and found near-universal enrichment of nerve axonal guidance genes in cancer-associated fibroblasts (CAFs), which we termed “neural-CAFs”. These CAFs were enriched near sites of perineural invasion (PNI), coinciding with regions of increased tumor cell proliferation and were most prevalent in metastatic recurrence lesions compared to primary tumors and untreated metastases. These findings suggest that nerves promote neural-CAF polarization and may help explain the neural tropism of PDAC, in which PNI and nerve hypertrophy are histopathologic hallmarks. Despite the importance of PNI, nerves remain an understudied component of the PDAC TME, largely due to limited availability of models which rely on the use of murine models or cross-species cocultures using murine nerves. Furthermore, the specific nerve populations that contribute to PDAC pathogenesis remain incompletely defined. Molecular profiling of nerves in PDAC tissue reveals hypertrophy and tumor invasion involving both sympathetic and sensory fibers, often within the same nerve bundle. Thus, there remains a critical need to develop relevant models to advance studies of tumor-nerve crosstalk and define the contributions of distinct neural populations to PDAC progression. To overcome this limitation, we have established a pipeline to obtain fresh ex vivo organ donor-derived dorsal root (sensory) and celiac (sympathetic) nerve ganglia. We have previously described our collaboration with Gift of Life Michigan, a centralized organ procurement and allocation center located in close proximity to our laboratory, whereby we obtain organs made available for research (most commonly in the event of exhaustion of the recipient list which precludes transplantation). Notably, there is no warm ischemic time in the procured organs, allowing for maximal preservation of the cellular, transcriptomic, and morphologic profiling. These specimens can be either sectioned into 300 µm slabs using a vibratome or digested into smaller nerve aggregates and plated on collagen or geltrex-coated coverslips. Axon projections from nerve explants are visible by light microscopy after 7 days of culture, while glial cell outgrowth is observed after 7 days of culture. Furthermore, we found that a subset of patient-derived PDAC organoids readily invade explants, and that invasion in accelerated with CAF co-culture. Future studies will compare invasion into sympathetic versus sensory nerve explants and identify the determinants that distinguish invasive from noninvasive PDAC organoids. Despite emerging RAS-directed therapies, outcomes in PDAC remain poor. Identifying targetable mediators of PNI may uncover new strategies to limit disease progression.