Abstract B046: Discovery of a fibroblast subtype enriched in long-term survivors of PDAC

Abstract Pancreatic ductal adenocarcinoma (PDAC) has a poor survival rate, with current 5-year overall survival estimates to be ∼13%. Surgical resection is currently the only potential cure for PDAC patients. Despite this, over 80% of patients experience disease recurrence post-resection. Through the study of rare PDAC long-term survivors (LTS), we can nominate novel targets or therapeutic approaches to advance patient care. Prior work implicated high-quality mutation-encoded neoepitopes combined with CD8+ T cell infiltration, but importantly neither factor alone, as strongly correlated with improved patient survival. These discoveries directly informed novel therapeutic approaches and early-phase clinical trials. However, it is currently unknown whether other cell subtypes and/or transcriptomic states can influence the tumor immune microenvironment (TME) dynamics and patient outcome. Here, we profiled 25 treatment-naïve PDAC surgical resection specimens at the single-cell transcriptomic level. Specifically, we leveraged the 10X Genomics FLEX single-cell RNA-seq chemistry, enabling investigation of archived samples and facilitating robust capture of fragile cell types. PDAC patients were categorized as short-term survivors (STS; n=13), with a median survival of 1 year (range 0. 3 – 2. 4 years), or LTS (n=12) with a median survival of 5. 8 years (range 3. 3 - 9. 1 years). After filtering, a total of 73, 969 high-quality cells were retained for analysis. We identified a total of 16 clusters including robust capture of malignant cells, cancer associated fibroblasts (CAFs), myeloid and lymphoid immune cell subsets, among others. Malignant cells from LTS patients more frequently demonstrated a classical PDAC subtype transcriptomic signature. Conversely, a basal transcriptomic signature was more prominent within STS malignant cells. In contrast to prior efforts using enzymatic dissociation of fresh tumors, CAFs were the most abundant cell type in most resection samples, accounting for 25% of total cells captured. Sub-clustering of CAFs uncovered six transcriptomic subsets, with cluster 5 (c5) CAFs significantly enriched within LTS patients compared to STS. We employed ligand-receptor analysis to nominate potential intercellular signaling networks of interest between c5 CAFs and immune cell subsets. While we observed numerous significant interactions, CCL19-CCR7 was the most significant signaling pathway between the c5 CAFs and TCF7+CD4+ T cells (TCF7+CD4+), in addition to dendritic cells (DCs). Moreover, c5 CAFs were significantly associated with higher numbers of both TCF7+CD4+ and DCs. We next investigated c5 CAF levels in relation to patient survival. Survival analyses determined c5 CAF levels to be an independent prognostic indicator within our patient cohort. Collectively, these data indicate a potential involvement of c5 CAFs in immune cell recruitment within the PDAC TME, offering future opportunities to leverage these findings through augmentation of immunotherapy with the aim of improving immune cell infiltration and response. Citation Format: Alex E. Blain, Zachary J. Kulstad, Sudarsana Addepalli, Connor J. Hennessey, Leigh Culnane, James M. Cleary, Simona Cristea, Andrew J. Aguirre, William A. Freed-Pastor. Discovery of a fibroblast subtype enriched in long-term survivors of PDAC 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 B046.