Primary malignant brain tumors bear dismal prognoses, with one quarter of patients surviving beyond five years of diagnosis (1). Glioblastoma cells in particular are fiercely invasive, often migrating several centimeters from the tumor resection cavity into eloquent brain (2). Due to inadequate treatment, high-grade gliomas require alternate, cell-specific treatments such as immunotherapy. Thus far several immunotherapy trials for glioma have shown promising results (3-6), but we lack knowledge on how to reproducibly mount an anti-tumor immune response. Over 1,000 cancer vaccine trials have and continue to involve the culture of tumor cells as the antigen source. Little was known on the influence of oxygen on the immunogenicity of cultured tumor cells until our recent findings that culture in 5% O2 increases: (1) glioma-associated antigen expression (Ref 8); and (2) adjuvanticity of glioma lysates (7, 8). These findings led to the identification of the protein annexin A2 (A2 hereafter), a novel immune adjuvant enriched in glioma cells grown in 5% O2. I hypothesized that A2 is a damage-associated molecular pattern and determined that it is a potent toll-like receptor 2 (TLR2) ligand. A2's TLR2 activity, in addition to the powerful CD8 T cell responses in mice given lysate vaccines from 5% O2, led to the hypothesis that A2 increases cross presentation of tumor antigens. In vitro data indicate that A2 boosts cross presentation on dendritic cells (DCs), which are capable of priming anti-tumor CD8 T cells; however, the precise mechanisms are unclear. To test this hypothesis, this proposal will be divided into two separate specific aims: (1) Investigate annexin A2's effect on antigen uptake, routing, and proteolysis: a. Measure uptake of labeled antigens and tumor lysate in DCs; b. Determine the subcellular location of antigen using microscopy of DCs; and c. Quantify proteasome activity and composition in DCs. (2) Determine if A2 potentiates T cell receptor signaling, expansion of tumor-reactive CD8 T cells, and extends survival of glioma-bearing mice: a. Quantify relative T cell receptor signal strength in glioma-reactive CD8 T cells;b. Measure expansion of endogenous glioma-reactive CD8 T cells c. Determine if A2/glioma peptide vaccination extends survival of glioma-bearing mice, and if survival correlates with ex vivo CD8 T cell response. Completion of these studies, basic-science cancer and immunology training, and medical school training focused on cancer therapy will prepare me for a career as a physician-scientist with a research program in brain tumor immunotherapy.
Cancers that begin in the brain are only mildly improved by current treatments. Vaccine therapy has the potential to alert the body of the tumor, eliminate it, and leave healthy tissues intact. This proposal investigates a new method to enhance the start of the immune response against tumors.
