Nanoengineered Macrophages Armed with TLR7/8 Agonist Enhance Remodeling of Immunosuppressive Tumor Microenvironment

Although adoptive cell-based therapy is illuminated as one of the promising approaches in cancer immunotherapy, it shows low antitumor efficacy because transferred cells adapt and alter toward a pro-tumoral phenotype in response to the tumor's immunosuppressive milieu. Herein, nanoengineered macrophages anchored with functional liposome armed with cholesterol-conjugated Toll-like receptor 7/8 agonist (masked TLR7/8a, m7/8a) are generated to overcome the shortcomings of current macrophage-based therapies and enhance the remodeling of the immunosuppressive tumor microenvironment (TME). The liposome-anchored macrophages (LAM phi-m7/8a), are fabricated by anchoring dibenzocyclooctyne-modified liposome(m7/8a) onto azido-expressing macrophages via a bio-orthogonal click reaction, are continuously invigorated due to the slow internalization of liposome(m7/8a) and sustained activation. LAM phi-m7/8a secreted approximate to 3 and 33-fold more IL-6 and TNF-alpha than conventional M1-M phi, maintained the M1 phenotype, and phagocytosed tumor cells for up to 48 h in vitro. Both intratumoral and intravenous injections of LAM phi-m7/8a induced effective antitumor efficacy when treated in combination with doxorubicin-loaded liposomes in 4T1-tumor bearing mice. It not only increases the infiltration of antigen-specific CD8+ T cells secreting granzyme B, IFN-gamma, and TNF-alpha within the TME, but also reduces myeloid-derived suppressor cells. These results suggest that LAM phi-m7/8a may provide a suitable alternative to next-generation cell-based therapy platform. Liposome-anchored macrophages (LAM phi-m7/8a), containing cholesterol-conjugated TLR7/8 agonist (masked TLR7/8a, m7/8a), consistently maintained the M1 phenotype and functions, showing enhanced antitumor efficacy. When combined with doxorubicin, LAM phi-m7/8a demonstrated potent antitumor effects in 4T1-tumor bearing mice through a substantial decrease in immune-suppressing cells and enhanced antigen-specific CD8+ T cell responses, suggesting a promising alternative for cell-based cancer therapy.image