Personalized Cancer Vaccine Development for Brain and Colon Cancers Using Synthetic HDL Nanoparticles

Abstract

Immunotherapy is an attractive treatment option for many cancers because it has the potential to reverse the immunosuppressive tumor microenvironment, target tumor antigens, and maintain a long-lasting anti-tumor response. Brain cancers are top candidates for such therapies because current standard-of-care is limited to surgery, radiation, and chemotherapy; surgery often fails to resect 100% of the tumor, and delivery of chemotherapeutic drugs to the brain is very inefficient due to the blood-brain barrier’s tightly regulated microenvironment. New immunotherapies for colon cancers are also being explored because of the difficulties of resection, surgery, and adverse effects associated with current targeted therapies and immune checkpoint blockade. Thus, drug delivery vehicles are being designed to carry antigens and other immunostimulatory molecules directly to tumors or tumor-draining lymph nodes for site-specific treatment that is minimally invasive and reduces off-target side effects. Within this dissertation, we explored (1) the ability of sHDL nanodiscs to deliver neoantigens for glioblastoma multiforme (GBM) to exert specific anti-tumor effects, (2) whether immunogenicity of colon adenocarcinoma neoantigen-loaded sHDL nanodiscs following formulation simplification is retained, and (3) the ability of sHDL nanodiscs to co-deliver chemo- and immuno-therapeutic entities to colon adenocarcinoma tumors. In the first project, we found that delivery of neoantigens by sHDL nanodisc was significantly more effective compared to delivery of soluble neoantigens in neoantigen-specific CD8+ T cell production, tumor growth reduction, and survival prolongation in murine GBM models. These anti-tumor effects were augmented by the addition of immune checkpoint blockade anti-PD-L1, and neoantigen-loaded sHDLs in combination with anti-PD-L1 reversed immunosuppression within the tumor microenvironment by significantly increasing CD8+ T cells and decreasing their PD-1 expression and Treg frequencies within the tumor. In the second project, we showed that we were able to simplify our formulation process for neoantigen-loaded sHDL through chemical modification of two neoantigen peptides using short-chain PEG and lipoprotein films. We verified that the simplified PEGylated formulations induced neoantigen-specific CD8+ T cell expansion similar to our traditional formulations. Although prophylactic vaccination did not slow MC38 colon adenocarcinoma tumor growth or extend overall survival equally between the two neoantigens Reps1 and Adpgk, we did see that PEGylated formulations and traditional formulations exhibited anti-tumor efficacy similar to each other. Together, these results indicated that nanovaccine synthesis could be streamlined for clinical translation. In the third project, we demonstrated the therapeutic advantage of co-delivering chemo- and immune-therapeutic entities on sHDL nanodiscs in a murine colon adenocarcinoma model. In vivo evaluation of docetaxel-loaded sHDL (DTX-sHDL) co-loaded with CpG revealed that CpG significantly improved the antitumor efficacy of DTX, suppressing tumor growth and prolonging survival in mice treated with DTX-sHDL/CpG as compared to mice treated with DTX-sHDL or DTX alone. Complete responses were achieved in two of the seven mice treated with DTX-sHDL/CpG without inducing any systemic toxicities, supporting the hypothesis that combination therapy with an immuno-stimulatory component would augment the antitumor efficacy of chemotherapy alone. In full, this dissertation (1) exposed a highly efficacious, tumor-specific, and personalized nanovaccine design for improving treatment of patients with Glioblastoma multiforme (GBM), (2) streamlined the neoantigen-sHDL nanovaccine formulation process for clinical translation, and (3) proposed an efficient method for co-delivery of chemo- and immuno-therapeutic entities for site-specific, non-toxic cancer treatment using sHDL nanodiscs. We believe that sHDL nanodiscs are versatile drug delivery vehicles and could set the stage for personalized and combinatorial cancer nanovaccine design.