Prostate cancer vaccines: maximizing a suboptimal immune response for improved outcome.

As approaches toward isolating tumor-associated antigens have become more refined, vaccines composed of novel cell surface proteins, peptides, or DNA encoding the molecule of interest have been developed. All of these approaches have in some way been shown to break immunologic tolerance, either by the generation of high-titer antibodies against the immunogen or by eliciting T-cell responses as shown by T-cell proliferation assays or specific cytokine release via enzyme-linked immunosorbent spot. No single immunologic approach to date has successfully shown significant durable disease remission in prostate cancer, albeit clinical trials using immune modulators together with vaccines have suggested that radiographic antitumor responses are feasible. This review updates the status of prostate cancer vaccines as tools for induction of active immunity and discusses the issues relevant to their clinical trial development.