Radioimmunoassay of Placental Alkaline Phosphatase in Ovarian Cancer Sera and Tissues

A specific radioimmunoassay for human placental alkaline phosphatase has been developed using the I-labeled enzyme, highly purified with a fast protein liquid chromatography system and an absorbed rabbit antiserum. The sensitivity of this assay was 0.2 U/L. Serum levels of over 0.2 U/L were found in 27% of ovarian cancer patients, and most of these elevated enzyme levels occurred with more advanced stages of the disease. On the other hand, almost all ovarian cancer tissue contained detectable levels of the enzyme. Serous adenocarcinoma, endometrioid adenocarcinoma, and dysgerminoma had particularly large amounts. Placental alkaline phosphatase was more frequently detected in tissue than in the serum of ovarian cancer, and therefore may be a useful target in immunodetection and immunotherapy and in studying the histopathology of ovarian cancer.