Androgen Receptor Targeted Vaccines for Prostate Cancer

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DESCRIPTION (provided by applicant): Prostate cancer is a significant worldwide health problem for which new treatments are needed. The goal of our research is to develop effective active immunotherapies, tumor vaccines, as a treatment for prostate cancer. In this application we propose to evaluate a novel immunotherapy target antigen, the ligand-binding domain of the androgen receptor (AR LBD), a biologically relevant molecule to prostate cancer growth and progression. We have previously demonstrated that patients with prostate cancer have existing humoral and cellular immune responses specific for the AR LBD, and that cytolytic CD8+ T cells specific for the AR LBD can lyse human prostate cancer cells in an HLA-A2 MHC class I-restricted fashion. In addition, we have demonstrated that a DNA vaccine encoding the AR LBD can elicit epitope-specific CD8+ T cells in an HLA-A2 transgenic mouse. Moreover, we have previously shown that increased expression of Hsp72 can increase MHC class I expression and antigen presentation. In the current proposal we hypothesize that a DNA vaccine encoding the AR LBD can elicit peptide- specific anti-tumor immune responses, and that modifications to a DNA vaccine permitting increased antigen presentation can augment anti-tumor immune responses. This will be evaluated in HLA-A2 transgenic mice, and in an HLA-A2-expressing transgenic mouse model of prostate cancer. For all of these studies we will focus on the ligand-binding domain (LBD) of the protein only, and will use the generation of responses to specific HLA-A2 epitopes as a read-out for immunological efficacy, markers which can be similarly used in a human clinical trial. In addition, we will evaluate whether DNA vaccines encoding hsp72 and/or a proteasome-targeting signal within a DNA vaccine can augment antigen presentation and antigen-specific cytolytic T- cell (CTL) responses, and anti-tumor immune responses in vivo. Finally, based on these results, we will conduct a phase I clinical trial to evaluate the safety and immunological efficacy of a DNA vaccine encoding the AR LBD, with or without modifications to facilitate antigen presentation, in patients with castrate-resistant, nonmetastatic prostate cancer. The specific aims of the proposal will be: 1) to determine whether a DNA vaccine encoding the AR LBD can elicit antigen-specific CD8+ T-cells and anti-prostate tumor responses in HLA-A2 transgenic mice; 2) to determine whether co-expression of Hsp72 or a proteasome-targeting signal with a model antigen in the context of a DNA vaccine can augment antigen-specific CD8+ T-cell effector immune responses and anti-tumor responses in HLA-A2-expressing transgenic mice; and 3) to determine the safety and immunological efficacy of a DNA vaccine encoding the AR LBD, with or without co-expression of Hsp72 and/or a proteasome-targeting signal, in patients with castrate-resistant nonmetastatic prostate cancer.