Circulating Prostate-Specific Antigen/CD14-Double-Positive Cells: a Biomarker Indicating Low Risk for Hematogeneous Metastasis of Prostate Cancer

Extract

The presence of cells in the blood stream of prostate cancer patients that stain positively for both prostatespecific antigen (PSA) and for the monocyte marker CD14 seems to indicate a low risk of metastasis formation. This cellular biomarker might be helpful in the assessment of the prognosis for prostate cancer patients with organ- restricted disease. It could be used to define a subgroup of patients with a low risk of life-threatening bone metastasis, although these patients show evidence of circulating prostate cancer cells by flow cytometry ( 1 ) or PSAPCR2 ( 2 ).

We describe here 16 patients with N0M0 stage prostate cancer and 11 patients with prostate cancer with bone metastasis (stage M1) as well as two control groups (eight patients with bladder cancer and nine patients with benign prostatic hyperplasia). So that we could determine the number of PSA/ CD14-double-stained cells in the peripheral blood of the patients by flow cytometry, 10 mL of EDTA-treated blood was drawn from the patients by venipuncture, and the erythrocytes were depleted by density-gradient centrifugation. The cells were stained simultaneously with anti-PSA-fluorescein isothiocyanate (FITC) (Coulter-Immunotech, Hamburg, Federal Republic of Germany) and an antibody labeled with CD14-phycoerythrin (PE) (Dianova, Hamburg). Controls for nonspecific binding of the antibody, negative controls with blood from healthy women, and positive controls with LNCaP cells were performed. The PSA-positive and PSA/CD14-double-positive cells were counted by a count gate discrimination procedure adjusted to the exclusion of nonspecific, stained cells in the FL1 (FITC)/FL2 (PE) plot of the negative control; two million peripheral white blood cells were analyzed for each sample after erythrocyte depletion.