Alkaline phosphatase as tumor marker

Applications and limitations of alkaline phosphatase as a tumor marker are discussed. This review focuses on three characteristic isoenzymes that have been found in the serum of cancer patients: (1) the Regan isoenzyme in bronchogenic carcinoma; (2) the Nagao isoenzyme in pleuritis carcinomatosa; and (3) the hepatoma alkaline phosphatase. Tumor variants of alkaline phosphatase are classified based on their heat stability properties resembling or differing from the placental isoenzyme. They can also be differentiated in their behavior to specific inhibitors. The presence of electrophoretic variants and enzyme-immunoglobulin complexes in other cancers are also described.