Perfluorocarbon nanoparticle-mediated platelet inhibition promotes intratumoral infiltration of T cells and boosts immunotherapy.

Cancer immunotherapy can stimulate and enhance the ability of the immune system to recognize, arrest, and eliminate tumor cells. Immune checkpoint therapies (e.g., PD-1/PD-L1) have shown an unprecedented and durable clinical response rate in patients among various cancer types. However, a large fraction of patients still does not respond to these checkpoint inhibitors. The main cause of this phenomenon is the limited T-cell infiltration in tumors. Therefore, additional strategies to enhance T-cell trafficking into tumors are urgently needed to improve patients' immune responses. In this study, we screened an array of perfluorocarbon compounds, reporting that albumin-based perfluorotributylamine nanoparticles (PFTBA@Alb) can effectively increase the permeability of tumor blood vessels, and no distinct side effects were found on normal blood vessels. After i.v. administration of PFTBA@Alb, the number of tumor-infiltrating CD8+ and CD4+ T cells showed an obvious rising trend. More important, a striking tumor inhibition rate, reaching nearly 90%, was observed when combining PFTBA@Alb with anti-PD-L1 antibody. These findings suggest that PFTBA@Alb can be regarded as an enhancer for anti-PD-L1 immunotherapy.