A lipid nanosystem establishes precise NO concentration gradient around tumor vessels via endothelial transcytosis, thereby normalizing tumor vasculature and creating an environment beneficial for antitumor immunotherapy

Abnormal tumor vasculature greatly accelerates tumor progression and diminishes antitumor treatments. Restoring perivascular NO gradients is available to maintain tumor vessel homeostasis and promote tumor vascular normalization. However, exogenously delivering NO strategies lacks the durability to maintain precise NO localization around tumor vessels. Herein, we design a lipid nano delivery system (MC@L) and exploit endothelial transcytosis to deliver metformin (Met) and CaO 2 into tumor vascular endothelial cells (ECs) and tumor cells for achieving tumor vascular normalization-boosted antitumor immunotherapies. The Ca 2+ and Met released in ECs could restore perivascular localization of NO by activating endothelial NOS (eNOS). Additionally, MC@L internalized by tumor cells could cause CaO 2 -induced immunogenic cell death (ICD), together with hypoxia relief and acid neutralization mediated by O 2 generation and H + consumption during CaO 2 degradation, thus further improving the immune effector cell functions under the accompaniment of Met-mediated inhibition of tryptophane uptake in tumor cells. Such a lipid nano delivery system greatly increases the susceptibility of 4T1 tumor-bearing mice to PD-L1 blockade efficacy.