Acid phosphatase isozymes in cancer of the prostate.

Abstract

Acid phosphatase (AP-ase) isozymes were studied in prostatic carcinoma, to determine to what extent they remain active and unchanged. In contrast to serum AP-ase, that of tissue homogenates was relatively stable. Tartrate-sensitive AP-ase activity varied 100-fold for lesions taken from 11 different patients, without complete loss of activity in any lesion. The results explain why the serum AP-ase activity is not invariably elevated even in patients with metastatic cancer of the prostate. An equation is given that permits estimation of the conditions under which secretion by the tumor will result in a detectable rise in the serum level of this enzyme. There was a close parallel between AP-ase activity determined by test-tube assay with phenyl phosphate as substrate, and activity determined by disc electrophoresis and development of isozyme bands with naphthol AS-BI phosphate. Disc electrophoresis of prostate from normal adults and from patients with benign prostatic hypertrophy showed a fine structure of multiple isozyme bands, which was largely acquired during fetal development. Samples of primary and metastatic cancer of the prostate showed variable loss of normal prostatic isozyme bands, but some of these changes may have been artifactual. An AP-ase isozyme band shared between fetal prostate and prostatic carcinoma, but absent from normal prostate, was not found.