Tumor cell-derived extracellular vesicles foster the immunosuppressive landscape of pancreatic cancer

Pancreatic cancer remains a devastating disease with limited therapeutic options. Accumulating evidence has shown that cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs), the predominant cells in the pancreatic cancer (PDAC) tumor microenvironment (TME), hinder anti-tumor immunity. However, the role of extracellular vesicles (EVs) in such process is poorly understood. In this study, using human bone-marrow-derived monocytes and PDAC tumor cells, we show that tumor cell-derived EVs (TC-EVs) induced monocyte differentiation towards M2-like immunosuppressive CD200R+/PD-L1+/HLA-DR- macrophages that express ALOX15b, that we identify as an independent PDAC poor-prognosis biomarker using a human pancreatic cancer metacohort. We also demonstrate that TC-EVs reprogram human primary PDAC CAFs, causing a fibronectin network reorganization associated with changes in extracellular matrix (ECM) composition, including alterations of the Wnt pathway elements such as SFRP1 enrichment. We further reveal that monocytes cultured on rSFRP1-enriched ECM differentiate also into M2-like immunosuppressive macrophages. Lastly, we demonstrate that both directly and indirectly TC-EVs, or rSFRP1-enriched ECM, driven differentiated macrophages hindered T-cell activation and subsequent anti-tumor activity. Our findings highlight novel, dual mechanisms of TC-EVs-mediated crosstalk, involving Alox15b+-Macrophages and SFRP1+-CAFs, that simultaneously contribute to foster the immunosuppressive ecosystem of pancreatic cancer.