Decreased concentrations of prostate-specific antigen and human glandular kallikrein 2 in malignant versus nonmalignant prostatic tissue.

OBJECTIVES To study quantitatively the relative expression of human glandular kallikrein 2 (hK2) and prostate-specific antigen (PSA) in paired (from the same patient) cancerous and noncancerous prostatic tissue to evaluate whether these proteins are overexpressed or underexpressed in cancer. METHODS We studied 14 patients who underwent radical retropubic prostatectomy for prostate cancer. Cancerous and adjacent normal tissues were excised and then extracted to prepare cytosolic extracts. The extracts were analyzed for total protein, and for hK2 and PSA using sensitive and specific immunofluorometric procedures. RESULTS PSA was present in the prostatic extracts at about 50 to 100 times higher amounts than hK2. The correlation between PSA and hK2 values was good. Both prostate kallikreins were expressed more in noncancerous than in cancerous prostatic tissue. CONCLUSIONS Our results demonstrated that both PSA and hK2 are down-regulated in prostate cancer compared with noncancerous tissue. The degree of down-regulation was higher for PSA than for hK2. The mechanism and physiologic consequences of this down-regulation are unknown.