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A prostate-specific antigen, distinct from acid phosphatase, was identified by immunologic procedures in prostate tissues (normal, benign hypertrophic, and cancerous) and seminal plasma, as well as in sera of patients with prostatic cancer and of nude mice bearing human prostatic tumor. This antigen was shown by immunoperoxidase staining to be confined to epithelial cells comprising the prostatic ductal elements. Prostate antigen was purified from prostatic tissue and seminal plasma, and it was shown to have a molecular weight of 33,000-34,000 with no subunit component. The isoelectric point of purified antigen was around 6.9, though several unpurified isomers with different isoelectric points also were observed. Serum-borne prostate antigen showed a molecular weight of 90,000-100,000 but it exhibited a molecular weight of 36,000 in the presence of sodium dodecyl sulfate. A sandwich-type, peroxidase-linked immunosorbent assay capable of detecting 0.1 ng of the antigen per milliliter of blood was developed. With this technique, serum level of the antigen was found to increase in patients with prostatic cancer as compared with normal males. The prostate-specific antigen can be a useful marker for detection of prostatic cancer.

Rabbit antiserum raised against the crude extract of normal human prostatic tissue contained antibodies to a prostatic tissue-specific antigen as shown by immunoprecipitation techniques. Using this antiserum a prostate antigen was detected in normal, benign hypertrophic, and malignant prostatic tissues, but not in other human tissues. The prostate antigen was purified to homogeneity from prostatic tissues and showed a single protein band on analytical polyacrylamide gel electrophoresis and isoelectric focusing. This report thus presents the first demonstration of the purification of a prostate-specific antigen that does not represent prostatic acid phosphatase.

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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.