A macrophage-derived noncanonical WNT niche drives immune exclusion in pancreatic cancer

Abstract Background and Aims Pancreatic ductal adenocarcinoma (PDAC) is characterized by profound immune exclusion and resistance to immunotherapy. Although WNT signaling has been implicated in PDAC, its cellular source within the tumor microenvironment and its contribution to immune suppression remain poorly defined. This study investigated whether myeloid-derived WNT signaling promotes PDAC progression. Methods Transcriptomic data from human PDAC cohorts, including The Cancer Genome Atlas (TCGA), and published single-cell RNA sequencing datasets were analyzed. Macrophage-associated WNT5A expression in human PDAC biopsies was assessed using in situ hybridization and immunofluorescence. Macrophage-derived WNT secretion was genetically disrupted using macrophage-specific Porcn knockout mice in orthotopic and subcutaneous KPC tumor models. Lineage-resolved spatial organization of macrophage subsets was characterized using Ms4a3 fate-mapping double-reporter mice with immunofluorescence and imaging mass cytometry. Macrophages–CD8⁺ T cells interactions were assessed using tumor-educated macrophage conditioned media, pharmacologic ARG1 inhibition, and in vivo CD8⁺ T cell depletion. Results PDAC tumors with high macrophage signatures showed enrichment of noncanonical WNT signaling, and macrophage-associated WNT5A was detected in human biopsies. Disruption of macrophage-derived WNT secretion suppressed tumor growth, reversed immune exclusion, and enhanced cytotoxic CD8⁺ T cell infiltration. Spatial lineage-resolved analysis demonstrated progressive accumulation of Hexb⁺ tissue-resident macrophages that dominated advanced lesions and formed a WNT-rich niche closely associated with Trem2⁺Arg1⁺ monocyte-derived macrophages. Mechanistically, macrophage-derived noncanonical WNT activated a JNK/c-Jun-ARG1 axis that inhibited CD8⁺ T cell proliferation, an effect abolished by myeloid WNT loss. Conclusions Myeloid-derived noncanonical WNT establishes a lineage-structured macrophage niche that enforces immune exclusion in PDAC. Targeting macrophage-restricted WNT signaling represents a promising strategy to reprogram the PDAC immune microenvironment.