Abstract
Pancreatic ductal adenocarcinoma (PDAC) arises within an extensively remodeled microenvironment, yet tissue markers that distinguish invasive carcinoma from precursor lesions remain limited. Integrating four single cell RNA sequencing atlases comprising 324,662 cells from 26 patients, we identified cancer associated fibroblast expansion, accumulation of C1QA+ immunoregulatory macrophages, and depletion of a dendritic cell compartment expressing plasmacytoid markers. Fibroblasts were enriched for extracellular matrix and PI3K AKT programs and macrophages for an antigen-presentation program. We then examined the protein level correlates of these populations in a tissue proteomic reference framework of 356 samples spanning non diseased pancreas, normal-adjacent tissue, low and high grade intraductal papillary mucinous neoplasms (IPMNs), IPMN associated invasive carcinoma, and PDAC, prioritizing proteins that changed monotonically across the six histopathologic reference groups or marked tumor enriched cell types. Despite depletion of plasmacytoid dendritic cells, the principal source of type I interferon, the interferon stimulated protein ISG15, expressed by both fibroblasts and macrophages, increased monotonically toward PDAC. In exploratory cross-validated benchmarking of PDAC versus low and high grade IPMN, excluding IPMN-associated invasive carcinoma (145 versus 56 samples), CATB+EPIPL achieved an AUC of 0.98, with a sensitivity of 92% at an achieved specificity of 92%, exceeding protein abundance models of diagnostic IHC-associated markers (S100P+IMP3+maspin+MSLN, 0.79) and refitted published IPMN progression combinations (<0.91). Against non diseased pancreas, candidate and comparator panels performed similarly (AUC 0.99 1.00). These biologically informed tissue protein panels warrant independent validation, including immunohistochemical evaluation of EUS guided fine needle biopsy specimens and measurement in blood.