Gold Nanoparticle Delivery of Modified CpG Stimulates Macrophages and Inhibits Tumor Growth for Enhanced Immunotherapy

Gold nanoparticle accumulation in immune cells has commonly been viewed as a side effect for cancer therapeutic delivery; however, this phenomenon can be utilized for developing gold nanoparticle mediated immunotherapy. Here, we conjugated a modified CpG oligodeoxynucleotide immune stimulant to gold nanoparticles using a simple and scalable selfassembled monolayer scheme that enhanced the functionality of CpG in vitro and in vivo. Nanoparticles can attenuate systemic side effects by enhancing CpG delivery passively to innate effector cells. The use of a triethylene glycol (TEG) spacer on top of the traditional poly-thymidine spacer increased CpG macrophage stimulatory effects without sacrificing DNA content on the nanoparticle, which directly correlates to particle uptake. In addition, the immune effects of modified CpGAuNPs were altered by the core particle size, with smaller 15 nm AuNPs generating maximum immune response. These TEG modified CpG-AuNP complexes induced macrophage and dendritic cell tumor infiltration, significantly inhibited tumor growth, and promoted survival in mice when compared to treatments with free CpG

CD11b+Ly6G+ cells induced by dsRNA

PolyI:C, a synthetic double-stranded RNA analog, acts as an immune-enhancing adjuvant that regresses tumors via cytotoxic T lymphocyte (CTL)-dependent and CTL-independent fashions, the latter of which remains largely unknown. Tumors contain CD11b+Ly6G+ cells, granulocytic myeloid-derived suppressor cells (G-MDSCs), or tumor-associated neutrophils (TANs), which play a critical role in tumor progression and development. Here, we demonstrate that CD11b+Ly6G+ cells respond to polyI:C and exhibit tumoricidal activity in an EL4 tumor implant model. PolyI:C-induced inhibition of tumor growth was attributed to caspase-8/3 cascade activation in tumor cells, which occurred independently of CD8α+/CD103+ dendritic cells (DCs) and CTLs. CD11b+Ly6G+ cells acted as anti-tumor effectors because depletion of CD11b+Ly6G+ cells totally abrogated tumor regression and caspase activation after polyI:C treatment. CD11b+Ly6G+ cells that had been activated with polyI:C showed cytotoxicity and inhibition of tumor growth through the production of reactive oxygen species (ROS)/reactive nitrogen species (RNS). These responses were abolished in either toll/interleukin-1 receptor domain-containing adaptor molecule-1 (TICAM-1)-/- or interferon (IFN)-αβ receptor 1 (IFNAR1)-/- mice. Thus, our results suggest that polyI:C targets myeloid cells in tumors, where CD11b+Ly6G+ cells exhibit anti-tumor activity through TLR3/TICAM-1 and IFNAR pathways, independent of those in CD8α+/CD103+ DCs that prime CTLs