Method for identifying prostate cells in semen using flow cytometry.
BACKGROUND
Prostate-specific antigen (PSA) cannot differentiate benign prostatic hyperplasia (BPH), from prostatitis, or prostate cancer in the range of 4.0-10 ng/ml. An accurate cytologic or histologic assessment is necessary to confirm the proper diagnosis. The nature of a biopsy 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 (stage T1 to T2). Two patients provided repeat samples. In addition, 15 vasectomized or nonvasectomized individuals without evidence of disease provided semen samples. Three million cells fixed with 50% ethanol were stained by an antibody (7E11.C5) to prostate-specific membrane antigen (PSMA), Hybritech Antibody (399) to PSA, and cytokeratin 8 and 18. In addition to the antibodies described, a DNA stain To-Pro 3 was used to identify 2n-4n DNA containing cells. A dual laser, Becton Dickinson FACSCaliber cytometer, was used to analyze the samples.


RESULTS
All semen specimens contained diploid, cytokeratin 18-positive epithelial cells regardless of disease status. A clear difference between prostate cancer and normal prostate cell samples was observed using staining with 7E11.C5. The ratio of prostatic cells in the total epithelial cell population (PSMA:cytokeratin ratios) was calculated for each specimen. 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:cytokeratin ratio of 0.11. This difference was significant. PSA staining was variable and inconsistent.


CONCLUSIONS
This report demonstrates that human semen contains prostate cells that can be characterized and used in the clinical diagnosis of prostate cancer.
Cancer Research Division, Pacific Northwest Cancer Foundation, Seattle, Washington 98125-7001, USA.
R J
RJ
Barren
E H
EH
Holmes
A L
AL
Boynton
A
A
Gregorakis
A A
AA
Elgamal
O E
OE
Cobb
C L
CL
Wilson
H
H
Ragde
G P
GP
Murphy
D000328:Adult; D000954:Antigens, Surface; D014408:Biomarkers, Tumor / Q000032:analysis; D002268:Carboxypeptidases / Q000032:analysis; D003937:Diagnosis, Differential; D005434:Flow Cytometry / Q000379:methods*; D043425:Glutamate Carboxypeptidase II; D006801:Humans; D007633:Keratins / Q000032:analysis; D008297:Male; D008875:Middle Aged; D011467:Prostate / Q000166:cytology*; D011469:Prostatic Diseases / Q000175:diagnosis*; D012189:Retrospective Studies; D012661:Semen / Q000166:cytology*
D000954:Antigens, Surface; D014408:Biomarkers, Tumor; D007633:Keratins; D002268:Carboxypeptidases; C473848:FOLH1 protein, human; D043425:Glutamate Carboxypeptidase II