Cancer immunotherapy is the most promising method for tumor therapy in recent years, among which the macrophages play a critical role in the antitumor immune response. However, tumor-associated macrophages (TAMs) usually display the tumor-promoting M2 phenotype rather than the tumor-killing M1 phenotype. Moreover, the over-expressed CD47 on tumor cells severely hinders the function of macrophages by blocking the CD47/SIRPα pathway. Herein, a nano-assembly system of CHTR/siRNA was constructed through the host-guest interaction of a hyperbranched amino-functionalized β-cyclodextrin and immune agonist imiquimod (R848), while CD47 siRNA was loaded inside through electrostatic interaction. The Toll-like receptor (TLR) 7/8 agonist R848 can "re-educate" macrophages from the protumoral M2 phenotype to antitumoral M1 phenotype, while CD47 siRNA can down-regulate the "don't eat me" CD47 signal on the surface of cancer cells and enhance the phagocytosis of cancer cells by macrophages. Through the dual regulation of TAMs, the immunosuppressive tumor microenvironment was relieved, and the host-guest drug-carrying system resulted in synergistic immunotherapy effect on tumors and inhibited tumor growth. The facile self-assembly of nanodrug offers a new strategy in co-delivery of multiple therapeutic agents for cascade cancer immunotherapy.
Keywords: CD47; Host-guest nanodrug; Macrophages; Tumor immunotherapy; siRNA.
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