Dual-delivery of exosome inhibitor and immune-activating gene via lipid nano-assemblies for tumor immune evasion inhibition.

The tumor microenvironment, with its complex immune evasion mechanisms, significantly hinders the efficacy of anti-tumor immunotherapies, including immune checkpoint inhibitors. Consequently, there is a strong impetus for extensive research to elucidate the immunosuppressive mechanisms within the tumor microenvironment and to develop novel therapeutic strategies. In this study, we have developed a drug/gene delivery system (folate-modified GW4869-loaded siIRF3 nano-complex, FD9R-GW/siIRF3) designed to simultaneously target and inhibit two key immune evasion pathways in the tumor microenvironment. The folate receptor-mediated delivery of GW4869 to cancer cells and tumor-associated macrophages (TAMs) led to the suppression of biosynthesis and release of tumor-derived exosomes (TEXs) containing exosomal PD-L1. Furthermore, IRF3 gene silencing effectively inhibited the M2-type differentiation of TAMs, and suppressed the secretion of CC motif chemokine ligand 22 (CCL22) in cancer cells, consequently reducing the recruitment of regulatory T cells (Tregs). The efficacy of FD9R-GW/siIRF3 in impeding tumor immune evasion was substantiated by an augmented recruitment of cytotoxic T cells and a diminished M2 macrophage polarization in the folate receptor-expressing 4 T1 allograft breast cancer model. Furthermore, the combination of a-PD-1 immunotherapy with FD9R-GW/siIRF3 led to a significant enhancement in the antitumor immune response, as evidenced by the inhibition of circulating tumor-derived exosomal PD-L1.