Abstract B100: Spatial relationships between tumor subtypes and tumor-promoting CAFs with clinical implications

Abstract Cancer-associated fibroblasts (CAFs) are critical mediators of tumor-stroma crosstalk in pancreatic ductal adenocarcinoma (PDAC). While bulk and single-cell transcriptomic studies have uncovered CAF heterogeneity, the spatial organization of CAF subtypes and their physical interactions with tumor epithelial subtypes remain incompletely understood. Here, we integrate bulk, single-cell, and spatial transcriptomic datasets to systematically interrogate the molecular, cell, and spatial interactions between tumor-promoting CAFs (proCAFs), tumor-restraining CAFs (restCAFs), and basal-like versus classical tumor subtypes across multiple biological scales. Ligand-receptor analysis of single-cell RNA-seq data revealed robust signaling between proCAFs and basal-like tumor cells, particularly through integrin-mediated (COL11A1–ITGA11) pathways, suggesting subtype-specific stromal-epithelial crosstalk within distinct tumor microenvironments. Histopathologic validation via immunofluorescence staining confirmed that proCAF regions are preferentially located adjacent to tumor epithelium and are characterized by reactive, myxoid stroma, whereas restCAF regions exhibit a fibrous, hypocellular morphology. To further elucidate spatial relationships, we performed 10x Genomics Visium spatial transcriptomics on seven primary PDAC tumors. Application of the DeCAF classifier to Visium spots demonstrated a distinct radial gradient of proCAF expression, peaking at the tumor-stroma interface and diminishing with distance—indicative of spatial colocalization with basal-like programs. Notably, proCAF gene signatures were specifically enriched in stromal regions adjacent to basal-like tumor zones, while classical tumor regions were spatially associated with heterogeneous CAF compositions. This subtype-specific spatial organization and paracrine signaling may underlie the clinical observation that basal-like tumors are significantly more likely to co-occur with proCAF stroma (64. 5%, p = 2. 17e–5). Importantly, patients harboring both basal-like and proCAF subtypes exhibited the poorest clinical outcomes (median overall survival: 11. 0 months), compared to those with classical/restCAF profiles (median overall survival: 30. 4 months, p 0. 001). Collectively, these multidimensional data define spatially organized and functionally interactive tumor-stroma niches in PDAC. Our findings highlight a co-evolutionary relationship between proCAFs and basal-like tumor cells that contributes to an aggressive disease phenotype, and underscore the potential of spatially resolved tumor-stroma profiling for improving patient stratification and guiding therapeutic targeting of the tumor microenvironment. Citation Format: Xianlu Laura. Peng, Ian McCabe, Elena Kharitonova, Ryan Zhao, Changfei Luan, Arthi Hariharan, Jaewon Lee, Nancy Kren, Yi Xu, Joseph Kearney, Justin Su, Michelle LaBella, Susan Tsai, Brian Belt, Roheena Panni, David Linehan, Yuliya Pylayeva-Gupta, Alina Iuga, Naim Rashid, Jen Jen Yeh. Spatial relationships between tumor subtypes and tumor-promoting CAFs with clinical implications 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 B100.