Over the last decade, immunotherapies have been developed for the treatment of prostate cancer with the goal of generating anti-tumor immune responses. Vaccine-based treatments target the immune system to a specific antigen, or set of antigens, expressed by the tumor. Other therapeutic modalities, including androgen deprivation therapy, can result in tissue damage and have been demonstrated to elicit prostate antigen-specific immune responses. The evaluation of immune responses to individual tumor antigens in the context of these non-antigen-specific immunomodulatory treatments has been notoriously difficult and time-consuming. We have previously reported a panel of 125 commonly recognized prostate cancer-associated antigens identified from multiple IgG screening approaches. This panel included multiple cancer-testis antigens and antigenic proteins recognized by IgG in patients with chronic prostatitis or prostate cancer. In the current study we questioned whether this panel could be used to identify antigen-specific immune responses elicited in patients with prostate cancer following androgen deprivation. 125 lambda phage encoding these unique antigens were spotted in triplicate using a high-throughput, high-density SEREX methodology. Sera were obtained from 33 patients with prostate cancer collected pretreatment and three months post-androgen deprivation therapy. These sera were used to probe this panel and IgG antibody responses were detected and objectively quantified by densitometry. 31 sera sets met pre-specified criteria as adequate for analysis. Results demonstrated that autoantibodies were induced to 62 of the 125 antigens. IgG responses were elicited to 21 of the antigens in multiple patients, including MAD-Pro-34, MAD-CT-1, and LAGE-1, each of which have previously been demonstrated to be the targets of autoantibody responses in prostate cancer patients. IgG responses were detected to at least one protein in 18 of 31 patients, and to multiple antigens in 11 of 31 patients. These data demonstrate that androgen deprivation elicits IgG responses to prostate-associated proteins, and that responses can be detected using a panel of commonly recognized prostate antigens. Further studies will aim to characterize this panel and autoantibody profiles in patients treated with other non-antigen-specific immunotherapies or anti-prostate tumor vaccines.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5591.