PEDF-enriched extracellular vesicle for vessel normalization to potentiate immune checkpoint blockade therapy

Abstract

The abnormal tumor vasculature acts as the physical and functional barrier to the infiltration and activity of effector T cells, leading to the low response rate of immune checkpoint inhibitors (ICIs). Herein, antiangiogenic extracellular vesicles that enable normalization of the tumor-associated vasculature were prepared to potentiate the efficacy of ICIs. Small extracellular vesicles were exploited as the delivery platform to protect the antiangiogenic protein, pigment epithelium-derived factor (PEDF), from proteolytic degradation. Along with the physicochemical characteristics of the PEDF-enriched extracellular vesicles (P-EVs), their inhibitory effects on migration, proliferation, and tube formation of endothelial cells were investigated in vitro. In tumor-bearing mice, it was confirmed that, compared to bare PEDFs, P-EVs efficiently reduced vessel leakiness, improved blood perfusion, and attenuated hypoxia. Consequently, when combined with anti-PD-1 antibodies, P-EVs remarkably augmented the antitumor immunity, as evidenced by increased infiltration of CD8+ T cells and reduced regulatory T cells. These results suggest that P-EVs are promising therapeutics for tumors refractory to ICIs.