Serum prostate specific antigen binding alpha 1-antichymotrypsin: influence of cancer volume, location and therapeutic selection of resistant clones.

We examined by gel filtration chromatography (Sephacryl 200) sera from 73 untreated patients with peripheral zone prostatic cancer volumes of 1 to 17 cc as well as patients with clinical stages C and D2 cancer. We also examined the sera from 40 patients who had failed radiation or hormonal therapy to determine if clonal cell selection by these 2 therapies altered the binding of prostate specific antigen (PSA) to alpha 1-antichymotrypsin. Finally, we compared sera from 10 patients with benign prostatic hyperplasia (BPH) and 14 with large transition zone-BPH cancer. Without exception, of the total serum PSA recognized by the Hybritech Tandem-R, Yang Pros-Check, Abbott IMx and Ciba Corning ACS assays, 88 to 98% were complexed with alpha 1-antichymotrypsin in all cancer patients. The 10 patients with BPH showed less complexation (73 to 84%). These studies suggest that much of the quantitative differences among assays is determined more by relative differences in recognition of the free and complex forms of PSA than by calibration differences between assays.