RESUMEN
PURPOSE: Sipuleucel-T is an autologous cellular immunotherapy that targets prostatic acid phosphatase (PAP) and is available for treatment of men with asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer (mCRPC). In this single-arm, two-cohort, multicenter clinical study, potential racial differences in immune responses to sipuleucel-T in men with mCRPC were explored. PATIENTS AND METHODS: Patients' blood samples were obtained to assess serum cytokines, humoral responses, and cellular immunity markers pre- and post-treatment. Baseline cumulative product parameters (total nucleated and CD54+ cell counts, and CD54 upregulation) were evaluated. IgM titers against the immunogen PA2024, the target antigen PAP, prostate-specific membrane antigen (PSMA) and prostate-specific antigen (PSA) were quantified by ELISA. Cytotoxic T lymphocyte activity was determined by ELISpots, and cytokine and chemokine concentrations by Luminex. RESULTS: Twenty-nine African Americans (AA) and 28 non-African Americans (non-AA) with mCRPC received sipuleucel-T. Baseline total nucleated cell count, CD54+ cell count, CD54 expression, and cumulative product parameters were higher in non-AA. Although PSA baseline levels were higher in AA, there were no racial differences in IgM antibody and IFN-ï§ ELISpots responses against PA2024, PAP, PSA and PSMA pre- and post-treatment. Expression of co-stimulatory receptor ICOS on CD4+ and CD8+ T cells, and the levels of Th1 cytokine granulocyte-macrophage colony-stimulating factor and chemokines CCL4 and CCL5, were significantly higher in AA pre- and/or post-treatment. Despite no difference in the overall survival, PSA changes from baseline were significantly different between the two races. CONCLUSIONS: The data suggest that immune correlates in blood differ in AA and non-AA with mCRPC pre- and post-sipuleucel-T.