Naturally occurring prostate cancer antigen-specific T cell responses of aTh1 phenotype can be detected in patients with prostate cancer

BACKGROUND. Cytotoxic T cells (CTL) are considered one of the primary effec tor cell populations in antitumor immunity. Recent studies, however, have d emonstrated the critical importance of helper T cells (Th), specifically in terferon gamma (IFN gamma)-secreting Th1 cells, either by supporting an app ropriate CTL environment or br recruiting other effector cells. We evaluate d whether patients with prostate cancer ha ie naturally occurring Th-cell r esponses specific for two prostate cancer-associated antigens, prostate-spe cific antigen (PSA) and prostatic acid phosphatase (PAP), and whether Th1-t ype responses to these antigens could be detected. METHODS. Peripheral blood mononuclear cells (PBMC) were collected from 80 p atients with prostate cancer and 20 male controls without prostate disease. Th-cell responses were evaluated by measuring antigen-specific proliferati on. IFN gamma and IL-5 secretion in response to antigen stimulation was det ermined by enzyme-linked immunosorbent assay. RESULTS. T cell proliferative responses specific for PSA and PAP could be d etected in patients with prostate cancer. Six percent (5/80) of patients ha d T cell responses specific for PSA and 11% (9/80) for PAP. T cell response s specific for PSA were more prevalent in patients with metastatic disease (P = 0.02), whereas responses specific for PAP could be detected in patient s irrespective of disease stage. IFN gamma -producing Th cells, specific fo r both PSA and PAP, could be identified in patients with prostate cancer. CONCLUSIONS. Patients with prostate cancer can have detectable Th-cell resp onses specific for the prostate cancer-associated proteins PSA and PAP. The presence of antigen-specific Th1 immune responses in prostate cancer patie nts suggests that an immune environment capable of supporting antigen-speci fic CTL map exist in vivo. Prostate 47:222-229, 2001. (C) 2001 Wiley-Liss, Inc.