Rational design of Polymeric Hybrid Micelles to Overcome Lymphatic and Intracellular Delivery Barriers in Cancer Immunotherapy.

Poor distribution of antigen/adjuvant to target sites and inadequate induction of T cell responses remain major challenges in cancer immunotherapy because of the lack of appropriate delivery systems. Nanocarrier-based antigen delivery systems have emerged as an innovative strategy to improve vaccine efficacy. Here we present polymeric hybrid micelles (PHMs) as a simple and potent antigen/adjuvant co-delivery system with highly tunable properties. PHMs consist of two amphiphilic diblock copolymers, polycaprolactone-polyethylenimine (PCL-PEI) and polycaprolactone-polyethyleneglycol (PCL-PEG). PHMs with different proportions of cationic PCL-PEI were prepared and loaded with tyrosinase-related protein 2 (Trp2) peptide and adjuvant CpG oligodeoxynucleotide to generate the Trp2/PHM/CpG co-delivery system. Lymphatic and intracellular antigen delivery as a function of PCL-PEI proportion was evaluated in vitro and in vivo. PHMs containing 10% (w/w) PCL-PEI (Trp2/PHM10/CpG) showed the optimal balance of good distribution to lymph nodes, strong immunization effect after subcutaneous administration, and low toxicity to dendritic cells. In a mouse model of B16F10 melanoma, Trp2/PHM10/CpG showed significantly higher antigen-specific cytotoxic T lymphocyte activity and greater anticancer efficacy than Trp2/PHM0/CpG without PCL-PEI or a mixture of free Trp2 and CpG. These results provide new insights into how cationic segments affect the efficiency of antigen delivery by cationic nanocarriers. They also suggest that PHMs can serve as a structurally simple and highly tunable platform for co-delivery of antigen and adjuvant in cancer immunotherapy.

Combined delivery of a TGF-ß inhibitor and an adenoviral vector expressing interleukin-12 potentiates cancer immunotherapy.

Cancer immunotherapy appears to have a promising future, but it can be thwarted by secretion of immunosuppressive factors, such as transforming growth factor-ß (TGF-ß), which inhibits local immune responses to tumors. To weaken immune resistance of tumors and simultaneously strengthen immune responses, we developed a multifunctional polymer that could co-deliver hydrophobic TGF-ß inhibitor and an adenovirus gene vector to tumor sites. This co-delivery system sustainably released TGF-ß inhibitor SB-505124 and effectively transferred the adenovirus vector carrying the interleukin-12 gene. In addition, it significantly delayed growth of B16 melanoma xenografts in mice and increased animal survival. Mechanistic studies showed that this combination therapy enhanced anti-tumor immune response by activating CD4+ and CD8+ T cells, natural killer cells and interferon-γ secretion in the tumor microenvironment. STATEMENT OF SIGNIFICANCE: To weaken immune resistance of tumors and simultaneously strengthen tumors' immune responses, we synthesized a structurally simple, low-toxic but functional polymer ß-cyclodextrin-PEI to encapsulate a hydrophobic TGF-ß inhibitor SB-505124 and to complex adenovirus vectors expressing IL-12. This is the first report demonstrating that combining TGF-ß inhibitor with IL-12 could provide effective immunotherapy against melanoma by the sustainable release of SB-505124 and the effectible transduction of IL-12 gene in tumor cells. The rational delivery system presented a comprehensive and valued platform to be a candidate vector for co-delivering hydrophobic small-molecule drugs and therapeutic genes for treating cancer, providing a new approach for cancer immunotherapy.