Levels of placenta-specific tissue protein 12 (PP12) in serum during normal pregnancy and in patients with trophoblastic tumour.

A sensitive radioimmunoassay method has been developed to measure soluble placental protein 12. Using this method trace amounts of PP12 have also been detected in the sera of healthy non-pregnant subjects (24.0 +/- 6.15 micrograms/l). During normal pregnancy serum PP12 levels rose rapidly reaching a peak value of 139.90 +/- 40.26 micrograms/l at 18 weeks. Serial determinations of PP12 have been made in 31 patients with trophoblastic tumours (16 hydatidiform moles, 10 invasive moles and five choriocarcinomas). It has been found that in patients with hydatidiform and invasive moles its initial values are extremely high (342.9 +/- 257.9 micrograms/l and 279.3 +/- 103.1 micrograms/l, respectively), much exceeding the non-pregnant and normal pregnant values. After evacuation of hydatidiform moles serum-PP12 rapidly fell to the upper limit of normal at 21-28 days, and to normal values at 8-12 weeks after operation. In patients with invasive mole requiring chemotherapy the rate of fall of PP12 level was slower. In patients with choriocarcinoma serum-PP12 levels were moderately raised (59-132 micrograms/l) and followed the clinical course of the disease. Serum-PP12 levels would seem to be of less value in monitoring patients with trophoblastic tumours than other tumour-markers (hCG, and SP1).