A hallmark of effective cancer treatment is the prevention of tumor reoccurrence and metastasis to distal organs, which are responsible for most cancer deaths. However, primary tumor resection is expected to be curative as most solid tumors have been shown both experimentally and clinically to accelerate metastasis to distal organs including the lungs. In this study, we evaluated the efficacy of our engineered nasal nano-vaccine (CpG-NP-Tag) in reducing accelerated lung metastasis resulting from primary tumor resection. Cytosine-phosphate-guanine oligonucleotide [CpG ODN]-conjugated nanoparticle [NP] encapsulating tumor antigen [Tag] (CpG-NP-Tag) was manufactured and tested in vivo using a syngeneic mouse mammary tumor model following intranasal delivery. We found that our nasal nano-vaccine (CpG-NP-Tag), compared to control NPs administered after primary mammary tumor resection, significantly reduced lung metastasis in female BALB/c mice subjected to surgery (surgery mice). An evaluation of vaccine efficacy in both surgery and non-surgery mice revealed that primary tumor resection reduces CD11b+ monocyte-derived suppressor-like cell accumulation in the lungs, allowing increased infiltration of vaccine-elicited T cells (IFN-γ CD8+ T cells) in the lungs of surgery mice compared to non-surgery mice. These findings suggest that the combination of the target delivery of a nasal vaccine in conjunction with the standard surgery of primary tumors is a plausible adjunctive treatment against the establishment of lung metastasis.
Keywords: MDSCs; immune response; intranasal vaccination; lung metastasis; nanoparticles.