METHOD FOR IDENTIFYING PROSTATE CELLS IN SEMEN USING FLOW-CYTOMETRY

BACKGROUND. Prostate-specific antigen (PSA) cannot differentiate benig n prostatic hyperplasia (BPH), from prostatitis, or prostate cancer in the range of 4.0-10 ng/ml. An accurate cytologic or histologic assess ment is necessary to confirm the proper diagnosis. The nature of a bio psy tends to make it a selective test not frequently repeated. We are reporting a technique employing semen as a source for the differential diagnosis of prostate epithelial cells. METHODS. Eleven vasectomized and nonvasectomized prostate cancer patients provided semen samples (s tage T1 to T2). Two patients provided repeat samples. In addition, 15 vasectomized or nonvasectomized individuals without evidence of diseas e provided semen samples. Three million cells fixed with 50% ethanol w ere stained by an antibody (7E11.C5) to prostate-specific membrane ant igen (PSMA), Hybritech Antibody (399) to PSA, and cytokeratin 8 and 18 . In addition to the antibodies described, a DNA stain To-Pro 3 was us ed to identify 2n-4n DNA containing cells. A dual laser, Becton Dickin son FACSCaliber cytometer, was used to analyze the samples. RESULTS. A ll semen specimens contained diploid, cytokeratin 18-positive epitheli al cells regardless of disease status. A clear difference between pros tate cancer and normal prostate cell samples was observed using staini ng with 7E11.C5. The ratio of prostatic cells in the total epithelial cell population (PSMA:cytokeratin ratios) was calculated for each spec imen. A retrospective study of sixteen semen samples from 11 prostate cancer patients had a mean PSMA:cytokeratin ratio of 0.57, whereas the samples from 15 patients without evidence of cancer had a mean PSMA:c ytokeratin ratio of 0.11. This difference was significant. PSA stainin g was variable and inconsistent. CONCLUSIONS. This report demonstrates that human semen contains prostate cells that can be characterized an d used in the clinical diagnosis of prostate cancer. Prostate 36:181-1 88, 1998. (C) 1998 Wiley-Liss, Inc.