Dendritic cell-based immunotherapy of prostate cancer: immune monitoring of a phase II clinical trial.

We assessed both non- and peptide-specific immune responses in prostate cancer patients before and after immunotherapy with dendritic cells exogenously pulsed with the prostate-specific membrane antigen-derived peptides, PSM-P1 and PSM-P2. For all subjects, we observed that clinical responses were strongly associated with two indicators of immunocompetence: skin test responses to recall antigens and cytokine secretion by T cells after nonspecific stimulation. In a subset of responders, we observed cytokine secretion or cytotoxicity against the immunizing peptides or an immunodominant epitope from an influenza recall antigen. The clinical results support the use of monitoring for overall immunocompetence to help determine why a patient has or has not responded to therapy. Moreover, it could be useful as an inclusion criterion to select those more likely to benefit from treatment.