Immunosuppressive CD14+HLA-DRlow/− monocytes in prostate cancer

OBJECTIVE To determine if the levels of circulating myeloid‐derived suppressor cells increase with progression of prostate cancer (PCa); to determine if such cells could contribute to the relative inefficiency of PCa immunotherapy. MATERIALS AND METHODS We analyzed peripheral blood mononuclear cells isolated from untreated PCa patients (uPCa; N = 18; mean age ± SD: 72.1 ± 6.9 years), tPCa (N = 22; 72.8 ± 9.8 years) and age matched controls (AMC; N = 12; 68.8 ± 7.5 years). We quantified surface marker phenotype, differentiation potential, effects on T cell proliferation and intracellular cytokines. RESULTS We observed an unexpectedly high percentage of a type of myeloid‐derived suppressor cells, CD14+HLA‐DRlow/− monocytes, in tPCa (30.7 ± 15.0% of CD14+ cells) relative to AMC (4.1 ± 6.5%, P