Dissecting FAP+ Cell Diversity in Pancreatic Cancer Uncovers an Interferon-Response Subtype of Cancer-Associated Fibroblasts with Tumor-Restraining Properties.

UNLABELLED: Within the stroma of pancreatic ductal adenocarcinoma (PDAC), mesenchymal cells differentiate into cancer-associated fibroblast (CAF) subtypes that differentially mediate disease progression. Defining the regulatory mechanism and diversity of CAF subtypes could identify potential therapeutic strategies to harness the tumor-suppressive activities of CAFs. To address this, we utilized single-cell RNA sequencing to profile fibroblast activation protein-α (FAP)-expressing mesenchymal cells in human PDAC. The mesenchymal subpopulations in PDAC reflected mesenchymal cell heterogeneity found in the normal developing pancreas. In addition to characterizing inflammatory CAF and myofibroblastic CAF subpopulations in detail, the analysis uncovered a previously undescribed interferon-response CAF (ifCAF) subtype. Tumor-derived signals induced specific CAF subtypes from pancreatic stellate cells in an organoid-based coculture model, and time-course experiments revealed regulatory mechanisms that govern subtype formation. STING agonists promoted an ifCAF phenotype in vivo and in vitro. Importantly, induction of an ifCAF phenotype suppressed tumor cell invasiveness and induced an antitumor phenotype in tumor-associated neutrophils. Together, this study resolves FAP+ stromal cell heterogeneity in PDAC and identifies an ifCAF subtype that can be induced to suppress protumorigenic features of PDAC.

SIGNIFICANCE: Characterization of FAP+ mesenchymal cell heterogeneity in pancreatic cancer identifies a tumor-suppressive interferon-response cancer-associated fibroblast subtype that can be induced by stimulating type I interferon signaling using STING agonists.