Immunochemical studies of human placental alkaline phosphatase in normal and neoplastic tissues

Human placental alkaline phosphatase (hPLAP) is normally present in plasma membranes of syncytiotrophoblast microvilli. hPLAP is expressed by many malignant tumors and is considered to be useful as a tumor marker. The objective of the work was to develop immunochemical methods for detection of this marker. hPLAP was isolated from placenta using a procedure with preparative isoelectric focusing as a final purification step, and was used to obtain rabbit antisera. Anti-hPLAP antibodies were obtained by affinity chromatography on the immobilized hPLAP antigen and were used in immunoenzyme tests for detection of hPLAP in sera and tissues of cancer patients with different malignancies. Anti-hPLAP antibodies were also used for localization of hPLAP on the histological level. The described methods may be of use in cancer diagnostics and therapy.