The effectiveness of the commonly used therapy is low for treating triple-negative breast cancer (TNBC). Macrophages, accounting for up to 50% of the TNBC tumor mass, are involved in innate and adaptive immunity, which can serve as an effective weapon against TNBC via combined immunotherapy. Here, we engineered mannose and glycocholic acid-modified trimethyl chitosan (MTG) nanoparticles (NPs) encapsulating signal regulatory protein α (SIRPα) siRNA (siSIRPα, a macrophage checkpoint inhibitor) and mucin 1 (MUC1) pDNA (pMUC1, a therapeutic pDNA vaccine) (MTG/siSIRPα/pMUC1 NPs) for in situ educating macrophages via an oral route to exert the cooperative antitumor effects of siSIRPα and pMUC1. Orally delivered MTG-based NPs accumulated in the macrophages in lymph nodes and tumor tissues via the intestinal lymphatic transport pathway, leading to strong cellular immunity responses. Following the transfection of orally administered MTG/siSIRPα/pMUC1 NPs within the same macrophages, siSIRPα strengthened the pMUC1 vaccine-induced systemic cellular immunity, while pMUC1 enhanced siSIRPα-mediated macrophage phagocytosis, M1-phenotype polarization, and tumor microenvironment (TME) remodeling at the tumor sites, thereby inhibiting the growth and metastasis of TNBC. The simultaneous achievements of the mutual promotion of innate and adaptive immunity in the local TME and in the whole body suggested that MTG/siSIRPα/pMUC1 NPs would provide a promising paradigm for the combined immunotherapy of TNBC via oral delivery of genes.
Keywords: antitumor efficacy; combined immunotherapy; immune checkpoint inhibitor; lymphatic transport; macrophage; oral delivery; pDNA vaccine.