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BACKGROUND A phase II trial was conducted to assess the efficacy of infusions of dendritic cells (DC) and two HLA‐A2‐specific prostate‐specific membrane antigen (PSMA) peptides (PSM‐P1 and ‐P2). This report describes the evaluation of 37 subjects admitted with presumed local recurrence of prostate cancer after primary treatment failure. METHODS All subjects received six infusions of DC pulsed with PSM‐P1 and ‐P2 at 6‐week intervals. Clinical monitoring was conducted pre‐, during, and post‐phase II study. Data included: complete blood count, bone and total alkaline phosphatase, prostate markers, physical examination, performance status, bone scan, ProstaScint® scan, and chest X‐ray, as well as other assays to monitor cellular and humoral immune responses. RESULTS One complete and 10 partial responders were identified from this group based on National Prostate Cancer Project criteria, or on a 50% reduction of prostate‐specific antigen (PSA), or on a significant resolution in lesions (biopsy‐proven when possible) on ProstaScint® scan. CONCLUSIONS About 30% of study participants in this group showed a positive response at the conclusion of the trial. This study suggests that DC‐based cancer vaccines may provide an alternative therapy for prostate cancer patients whose primary treatment failed. Prostate 39:54–59, 1999. © 1999 Wiley‐Liss, Inc.

ABSTRACT:Dendritic cells (DCs) are "professional" antigen-presenting cells capable of stimulating T-cell proliferation and cytotoxicity when loaded with and presenting specific antigens, including tumor antigens. We demonstrated the stimulation of an autologous cytotoxic T-cell response elicited by DC loaded with autologous tumor cell lysate derived from primary prostate tumor. A candidate tumor antigen is prostate-specific membrane antigen (PSMA), which is overexpressed in prostate cancer patients. We identified a HLA-A2 motif in PSMA, isolated patient DC, loaded peptide into DC, and stimulated autologous T cells to proliferate. The ability to use DC for presentation of either tumor or peptide antigen in an HLA-restricted fashion in order to stimulate T-cell proliferation and cytotoxicity demonstrates the potential of this technology for development of a prostate cancer vaccine. 0 1996 Wiley-Liss, Inc.