Immunological checkpoint inhibitors provide a revolutionary method for
cancer treatment. However, due to low
tumor mutations and insufficient infiltration of immune cells into the tumor microenvironment, 85% of
colorectal cancer patients cannot respond to checkpoint blockade
immunotherapy. In this study, tumor microenvironment-responsive deformable nanoparticles (DMP@NPs) were rationally designed to improve
immunotherapy by synergistically modulating the immune tumor microenvironment. DMP@NPs self-assemble from a newly synthesized
tumor acidity responsive
polypeptide checkpoint inhibitor
polymer (PEG-DMA-DPPA-1) with immunogenic cell death (ICD) enhanced combination drugs containing a certain proportion of
mitoxantrone (MITX) and
proanthocyanidins (PC). Upon
tumor acidity-triggered cleavage of PEG-DMA-DPPA-1, DMP@NPs undergo special "sphere-ring deformation" dissociation, gradually releasing
polypeptide checkpoint inhibitor DPPA-1, MITX and PC. MITX/PC in vitro synergistically triggers higher ICD with the release of the high mobility group box-1 (HMGB-1) and
calreticulin (CRT). After
intravenous injection of DMP@NPs, the local tumor microenvironment of CT26
tumor-bearing mice was reprogrammed, and dendritic cell activation and T cell infiltration were significantly increased. Most importantly, the synergistic immune nanodrug DMP@NPs improved the efficacy of
colorectal cancer immunotherapy and reduced toxicity and side effects for the immune organs.