Ming C. Wang

Prostatic‐specific antigen: An immunohistologic marker for prostatic neoplasms

Antiserum to a human prostate‐specific antigen was raised in a rabbit and utilized by immunoperoxidase staining to evaluate its potential value as a diagnostic histologic marker for tumors of prostatic origin. All primary and metastatic prostatic malignancies reacted positively, whereas nonprostatic neoplasms did not stain with this procedure. This is the first immununohistochemical marker for prostate gland epithelium which does not represent prostatic acid phosphatase.

The proteolytic activity of human prostate-specific antigen

Human prostate-specific antigen has been found to exhibit a mild activity of protease at neutral pH. This finding is based on two observations: a proteolytic activity was always associated with the antigen fractions during purification, and the proteolytic activity and the antigen were precipitated with specific antibody to the antigen. In comparison with physico-chemical and catalytic properties of known proteases, human prostate-specific antigen is a distinct neutral protease.

A Simplified Purification Procedure for Human Prostate Antigen

Methods for purifying the human prostate specific antigen are described. The antigen was isolated from human prostate and seminal plasma. Purified antigen (ca. 1 mg/ml) from seminal plasma was immunologically identical and biochemically similar to that of prostatic tissue.

Expression of prostatic acid phosphatase in human prostate cancer.

By a specific immunochemical measurement, the activity of prostatic acid phosphatase (PAP) in prostate cancer was found to be about 25%, on average, based on micrograms DNA or per cell, of that in normal prostate or benign prostatic hypertrophy (BPH). The reduction of PAP in prostate cancer was further revealed by a decrease in PAP protein. The 125I-labeled anti-PAP IgG specifically bound to nascent peptides on PAP-synthesizing polysomes showed no qualitative differences among cancerous prostate, normal prostate and BPH. However, the quantitative binding of 125I-labeled anti-PAP IgG to polysomes of cancerous prostate was half that of normal prostate of BPH. These data suggest that a significant amount of PAP and its synthesizing polysomes was reduced in prostate cancer as a result of PAP gene suppression.

Isoenzymes of human prostate acid phosphatase.

The isoenzymes of human prostatic acid phosphatase have been studied by an isoelectric focusing technique. Purified acid phosphatase from malignant prostates contained eight isoenzymes with pI 4.4--5.3. The sera from patients with prostate cancer were shown to have similar acid phosphatase isoenzyme patterns at pI 4.0--5.5; as the serum enzyme activities increased, the pI of isoenzymes shifted to more acidic pH. These isoenzyme patterns of sera from patients with prostate cancer were different from those of patients with Gauchers disease or from acid phosphatase of human erythrocytes, both of which exhibited only one enzyme band around pI 5.0 and 6.0, respectively. Treatment of serum sample of prostate cancer with neuraminidase did not result in a single enzyme band but alter the pI of isoenzymes, which shifted to a higher pH region. The significance of acid phosphatase activities and its isoenzyme patterns in prostate cancer merits further investigation.