Neutrophil membrane-derived nanoparticle loading TLR7 agonists augments radiotherapy efficacy and boosts abscopal effect via regulating tumor microenvironment

Abstract

Background: Increasing evidence indicates that radiotherapy (RT) has synergistic inhibitory efficiency with immunotherapy agents in multiple cancers and enhances abscopal effects by regulating the innate immune response, which was further investigated in this study. Neutrophils are recruited in radiated tumors. Therefore, neutrophil membrane-coated nanoparticles potentially deliver R837 (Toll-like receptor 7 agonist) to radiated tumors. Methods: A novel nanoparticle R837@PLGA@Neu was prepared by initially assembling PLGA (poly (lactic-co-glycolic acid)) with R837 (TLR7 agonist) into R837@PLGA followed by coating with neutrophil membrane. Characterizations of R837@PLGA@Neu were performed. Tumor targeting efficiency was evaluated by in vivo fluorescent imaging of CT26-bearing mice. Treatments of R837@PLGA@Neu combined with RT were carried out in unilateral and bilateral CRC tumor-bearing mice, followed by validations of immune cells in tumors by flow cytometry. Results: The characteristics of R837@PLGA@Neu were well identified, and it was confirmed to have high uptake ability and low cytotoxicity in colorectal cancer (CRC) cells in vitro, as well as its strong tumor-targeting efficiency in vivo in CRC tumor-bearing mice. The exciting findings were that R837@PLGA@Neu combined with RT exerted prominent tumor inhibition not only in radiated tumors, but also in distant tumors without RT, suggesting its enhancement of the efficacy and abscopal effect of RT. The possible underlying mechanisms were remodeling of the tumor microenvironment by triggering mature dendritic cells and CD8+ T cells. Conclusion: In summary, our findings suggested that neutrophil membrane-derived nanoparticle R837@PLGA@Neu with high uptake ability and low cytotoxicity showed strong tumor-targeting efficiency, and combination with RT had a promising effect in CT26-bearing mice via immune cell regulation. Our results provide a probable combination strategy for CRC treatment.