Tumour immunosuppressive microenvironments inhibit antigen-specific cellular responses and interfere with CpG-mediated immunotherapy. Overcoming tumour microenvironment (TME) immunosuppression is an important strategy for effective therapy. This study investigated the ability of a tumour-targeting IL-4Rα aptamer-liposome-CpG ODN delivery system to introduce CpG into tumours and overcome the immunosuppressive TME. The IL-4Rα-liposome-CpG delivery system was prepared. FAM-CpG visualisation was used to demonstrate tumour targeting in vitro and in vivo. Anti-tumour effects of this delivery system were evaluated in CT26 tumour-bearing mice. Mechanisms for conquering the TME were investigated. FAM-CpG was better distributed into the tumours upon treatment with IL-4Rα-liposome-FAM-CpG compared to distribution in the control group in vitro and in vivo. IL-4Rα-aptamer-liposome-CpG treatment inhibited distinct myeloid-derived suppressor cell populations in tumours and bone marrow. Similar profiles were observed for regulatory T cells in tumours. In CT26 tumour-bearing mice, IL-4Rα-liposome-CpG treatment exhibited enhanced anti-tumour activity. Increased mRNA levels of TNF-α, IL-2, and IL-12, and decreased mRNA levels of VEGF, IL-6, IL-10, MMP9, arginase-1, inducible NOS, CXCL9, p-Stat3, and NF-κB were observed in tumours upon IL-4R-liposome-CpG-treatment. The results suggested that pharmacologic targeting by the IL-4R aptamer-liposome-CpG system improves TME therapeutic benefit and provides a rationale for cancer immunotherapies.
Keywords: CpG; IL-4Rα; aptamer; myeloid-derived suppressor cell; tumour microenvironment.