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.

Public Health Relevance

Prostate cancer is a significant worldwide health problem, and the second leading cause of cancer-related death in men in the United States. New treatments for prostate cancer are urgently needed. The goal of this research is to develop effective anti-tumor DNA vaccines as a treatment for cancer, and prostate cancer in particular. Thus, this proposal is directly relevant to the mission of the National Cancer Institute. This proposal will characterize and evaluate a new vaccine target antigen in prostate cancer, the ligand binding domain of the androgen receptor. The androgen receptor has been the key pharmacological target for metastatic prostate cancer treatment for over 50 years, but there has been no previous evaluation of this as an immunological target antigen. In addition, our project seeks to identify means of increasing the efficacy of DNA vaccines by increasing presentation of the target antigen at the time of immunization. As such the results from these studies should be widely applicable to other genetic vaccines. Finally, this proposal will evaluate these findings in a human clinical trial in patients at high risk for prostate cancer metastatic recurrence.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Cancer Immunopathology and Immunotherapy Study Section (CII)
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Yovandich, Jason L
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University of Wisconsin Madison
Internal Medicine/Medicine
Schools of Medicine
United States
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Olson, Brian M; Gamat, Melissa; Seliski, Joseph et al. (2017) Prostate Cancer Cells Express More Androgen Receptor (AR) Following Androgen Deprivation, Improving Recognition by AR-Specific T Cells. Cancer Immunol Res 5:1074-1085
Olson, Brian M; Bradley, Eric S; Sawicki, Thomas et al. (2017) Safety and Immunological Efficacy of a DNA Vaccine Encoding the Androgen Receptor Ligand-Binding Domain (AR-LBD). Prostate 77:812-821
Colluru, Viswa Teja; McNeel, Douglas G (2016) B lymphocytes as direct antigen-presenting cells for anti-tumor DNA vaccines. Oncotarget 7:67901-67918
Bloom, Jordan E; McNeel, Douglas G (2016) SSX2 regulates focal adhesion but does not drive the epithelial to mesenchymal transition in prostate cancer. Oncotarget 7:50997-51011
Colluru, V T; Johnson, Laura E; Olson, Brian M et al. (2016) Preclinical and clinical development of DNA vaccines for prostate cancer. Urol Oncol 34:193-204
Rekoske, Brian T; McNeel, Douglas G (2016) Immunotherapy for prostate cancer: False promises or true hope? Cancer 122:3598-3607
Rekoske, Brian T; Smith, Heath A; Olson, Brian M et al. (2015) PD-1 or PD-L1 Blockade Restores Antitumor Efficacy Following SSX2 Epitope-Modified DNA Vaccine Immunization. Cancer Immunol Res 3:946-55
McNeel, Douglas G; Gardner, Thomas A; Higano, Celestia S et al. (2014) A transient increase in eosinophils is associated with prolonged survival in men with metastatic castration-resistant prostate cancer who receive sipuleucel-T. Cancer Immunol Res 2:988-99
Smith, Heath A; Rekoske, Brian T; McNeel, Douglas G (2014) DNA vaccines encoding altered peptide ligands for SSX2 enhance epitope-specific CD8+ T-cell immune responses. Vaccine 32:1707-15
Olson, Brian M; Johnson, Laura E; McNeel, Douglas G (2013) The androgen receptor: a biologically relevant vaccine target for the treatment of prostate cancer. Cancer Immunol Immunother 62:585-96

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