Catalytic and immunologic activities of placental-like alkaline phosphatase in clinical studies. The value of PLAP in follow-up of ovarian cancer.

Placental-like alkaline phosphatase (PLAP) was measured by its catalytic activity (CA), using an amplified enzyme-linked immunoassay, and by its immunologic activity (IA), using an enzyme-linked immunosorbent assay. In both assays the same monoclonal anti-PLAP antibody was used as the primary reagent. This antibody reacts with the main epitope on PLAP that is common to PLAP of ovarian and testicular origin, as well as of PLAP that is induced by smoking. Determinations of CA and IA of PLAP were carried out in serum samples from 101 patients with epithelial ovarian cancer (49 patients with progressive or recurrent disease, 52 patients with no evidence of disease), 20 patients with testicular cancer (8 non-seminoma testis, 12 seminoma testis) and 61 healthy controls. Smoking status was taken into consideration. The main findings from this study are: 1. In prolonged follow-up of patients who were treated for ovarian cancer, progressive or recurrent disease was never accompanied by rising values of CA or IA of PLAP. Therefore in this study, PLAP was not a good monitor for this disease. 2. In all instances where expression of PLAP was reflected by raised serum levels of these antigens, the measurement of the catalytic activity proved to be a more sensitive parameter than that of the immunologic activity. The value of PLAP measurements in the follow-up of patients with testicular cancer remains to be elucidated.