Spherical Nucleic Acids as Vaccines Against Triple Negative Breast Cancer

Background: The development of a cancer vaccine for triple-negative breast cancer (TNBC) has been hindered because there are no known tumor-associated antigens. The administration of cell lysates derived from TNBC tumors has been investigated as a vaccination strategy to provide the immune system with all possible tumor-specific antigens and epitopes. However, this approach has only limited benefit and direct vaccination with lysates has resulted in poor immunogenicity and modest efficacy. Intriguingly, oxidation of tumor lysates has been found to increase immunogenicity, though the biochemical basis for this effect remains unclear. Importantly, nanoscale vaccines have been shown to elicit greater immune responses and antitumor effects than administration of simple mixtures of adjuvant with antigen. Further, we have recently shown that the kinetics of antigen release and presentation plays a vital role in vaccine efficacy. Objective: In preliminary studies, we found that packaging cell lysates from TNBC cell lines in the core of spherical nucleic acids (SNAs), whose shells are comprised of adjuvant DNA, results in superior antitumor activity as compared SNAs containing non-oxidized lysates or simple mixtures of oxidized lysate with adjuvant DNA. Herein, we propose to elucidate the chemical basis for the enhanced immunogenicity of the oxidized lysates, the structural basis for the enhanced efficacy observed when oxidized lysates are packaged in a nanoscale architecture, and to develop stimuli-responsive nanocarriers for lysate-based vaccines to control the kinetics of antigen release. Specific Aims: (1) elucidate how oxidized lysates differ structurally and chemically from lysates prepared without oxidation; (2) probe the effect of liposome stability on vaccine function; (3) increase the specificity of antigen release through the development of stimuli-responsive SNAs. Study Design: Oxidized lysates will be fractionated in various ways and immunogenicity via dendritic cell maturation. To elucidate the biochemical basis of oxidation-enhanced antigen immunogenicity, the most immunogenic fraction will be subjected to proteomic analysis and compared to its non-oxidized counterpart to identify differences in chemical structure between populations and. In tandem, the effect of liposome structure will be probed through preparation of a series of SNAs prepared from liposomes with different melting temperatures. The serum stability, immunostimulation, and efficacy of these compounds in a xenograft model of TNBC will be assessed. Finally, a novel polymeric SNA will be developed that is designed to release its cargo (lysate) only at endolysosomal pH. Cancer Relevance: These studies will significantly advance cancer research by enhancing our understanding of, and ability to treat, TNBC using cancer vaccines. Further, the knowledge gained will result in a set of design rules for vaccine development that can be applied to other cancer types.