SERUM PROSTATE-SPECIFIC ANTIGEN COMPLEXED TO ALPHA-1-ANTICHYMOTRYPSINAS AN INDICATOR OF PROSTATE-CANCER

Prostate specific antigen (PSA) in serum has recently been shown to oc cur in complex with alpha1-antichymotrypsin and as an approximately 30 kDa. noncomplexed molecular form. We characterized PSA by 3 different assays in samples from 144 patients with benign prostatic hyperplasia (BPH) and 121 with carcinoma of the prostate. One of these noncompeti tive assays measured total PSA by detecting PSA complexed to serine pr oteinase inhibitors and the noncomplexed molecular form, a second meas ured only PSA in complex with alpha1-antichymotrypsin, whereas a third detected the noncomplexed form. PSA in complex with alpha1-antichymot rypsin was the predominant form in all patient sera. Noncomplexed PSA constituted a minor fraction that was significantly smaller in patient s with untreated prostate cancer than in those with BPH (p <0.0001). T he proportion of noncomplexed PSA does not correlate to the serum conc entration of PSA or that of alpha1-antichymotrypsin. In men with a ser um PSA concentration of less than 10 mug./l. the combination of assays measuring total PSA immunoreactivity, the noncomplexed molecular, for m and PSA in complex with alpha1-antichymotrypsin may facilitate discr imination between prostate cancer and BPH.