PLAP

Placental alkaline phosphatase (PLAP) is an isoenzyme of alkaline phosphatase that is embedded in placental syncytiotrophoblast membrane through phosphatidylinositol. PLAP can participate in the regulation of placental calcium and phosphorus metabolism by catalyzing the hydrolysis of phosphate esters to produce inorganic phosphates. It can also become a receptor for immunoglobulin (Ig) to mediate the entry of IgG from the mother into the fetal blood, which indicates that PLAP plays a crucial role in fetal growth and development. Some clinical research suggested that PLAP is expressed to varying degrees in multiple germ cell tumors, including seminoma, endometrial adenocarcinoma, ovarian serous adenocarcinoma, ovarian dysgerminoma, and placental trophoblast cell tumor, which makes it become one of the differential diagnostic biomarkers. In addition, some scholars have found that PLAP is more present in highly differentiated tumors but expressed at lower level in poorly differentiated tumors.