Tumoral extracellular vesicles and particles reprogram interstitial macrophages in the lung to promote vascular permeability and metastasis.

The mechanisms by which tumor-derived extracellular vesicles and particles (EVPs) promote vascular permeability during premetastatic niche formation remain unclear. Here, we show that tumor EVPs rapidly induce vascular leakiness within 1 h of administration in female mice, creating a permissive environment that enhances metastatic seeding. Rather than acting directly on endothelial cells, EVPs activate NF-κB and JAK-STAT signaling in interstitial macrophages, leading to IL-6 secretion and increased vascular permeability. Interstitial macrophage depletion markedly reduces EVP-induced vascular leakiness and metastasis. We identify extracellular vesicle-associated integrin α5 (ITGα5) as a major functional determinant of this process, promoting macrophage activation and IL-6 secretion without affecting EVP uptake. EVPs derived from colorectal cancer tumors with high ITGα5 similarly induce macrophage IL-6 secretion and vascular permeability. Together, these findings define an EVP-macrophage-IL-6 axis that drives vascular permeability during premetastatic niche formation and identify EVP-associated ITGα5 as a key mediator of metastatic progression and a potential therapeutic target.