Amplified Cancer Immunotherapy of a Surface-Engineered Antigenic Microparticle Vaccine by Synergistically Modulating Tumor Microenvironment

Efficient cancer vaccines not only require the co-delivery of potent antigens and highly immunostimulatory adjuvants to initiate robust tumor-specific host immune response but also solve the spatiotemporal consistency of host immunity and tumor microenvironment (TME) immunomodulation. Here, we designed a biomaterials-based strategy for converting tumor-derived antigenic microparticles (T-MPs) into a cancer vaccine to meet this conundrum and demonstrated its therapeutic potential in multiple murine tumor models. The internal cavity of T-MPs was employed to store nano-Fe₃O₄ (Fe₃O₄/T-MPs), and then dense adjuvant CpG-loaded liposome arrays (CpG/Lipo) were tethered on the surface of Fe₃O₄/T-MP through mild surface engineering to get a vaccine (Fe₃O₄/T-MPs-CpG/Lipo), demonstrating that co-delivery of Fe₃O₄/T-MPs and CpG/Lipo to antigen presenting cells (APCs) could elicit strong tumor antigen-specific host immune response. Meanwhile, vaccines distributed in the TME could reverse infiltrated tumor-associated macrophages into a tumor-suppressive M1 phenotype by nano-Fe₃O₄, amazingly induce abundant infiltration of cytotoxic T lymphocytes, and transform a "cold" tumor into a "hot" tumor. Furthermore, amplified antitumor immunity was realized by the combination of an Fe₃O₄/T-MPs-CpG/Lipo vaccine and immune checkpoint PD-L1 blockade, specifically inhibiting ∼83% of the progression of B16F10-bearing mice and extending the median survival time to 3 months. Overall, this study synergistically modulates the tumor immunosuppressive network and host antitumor immunity in a spatiotemporal manner, which suggests a general cell-engineering strategy tailored to a personalized vaccine from autologous cancer cell materials of each individual patient.