Detection of circulating placental protein 5 in patients with trophoblastic tumors

Progesterone dependence and extratrophoblastic origin of pregnancy-associated plasma protein-A (PAPP-A) in early pregnancy

Pregnancy-associated plasma protein-A (PAPP-A) is a macromolecular glycoprotein produced in increasing concentration as pregnancy advances. PAPP-A is not specific to pregnancy since measurable levels have been found in non-pregnant females and in males. In non-pregnant females, PAPP-A is probably produced by the endometrium. The origin of PAPP-A in pregnant women is still controversial. In-vitro trophoblast and decidual explants both produce PAPP-A. So far, it is not known if the same applies to the in-vivo situation and to what extent these two tissues contribute to the circulating levels of PAPP-A. This study compares the circulating concentrations of PAPP-A and beta-hCG and progesterone in different pathological situations. In hydatidiform moles, beta-hCG levels are very high demonstrating an intense trophoblastic activity, whereas PAPP-A levels remain in the normal range. With spontaneous abortions, beta-hCG levels decline to very low values whereas PAPP-A continues to increase. These observations furnish indirect evidence for a major contribution to circulating PAPP-A levels by extratrophoblastic sites. Furthermore, PAPP-A levels decrease after administration of an anti-progesterone (RU486) either in-vivo or in-vitro. This is considered as a proof that PAPP-A levels in early pregnancy are progesterone dependent.

Prognostic significance of the new placental proteins in trophoblastic disease

Circulating levels of four specific placental proteins, human chorionic gonadotrophin (hCG), Schwangerschafts protein 1 (SP1), placental protein 5 (PP5) and pregnancy-associated plasma protein A (PAPP-A), were measured in 31 patients with hydatidiform mole before treatment. Seven patients subsequently developed clinical choriocarcinoma and three of them had pulmonary metastases. The estimations of hCG, PP5 and PAPP-A levels were found to be of no value in the prediction of malignant sequelae. Levels of SP1 greater than or equal to 16.5 i.u./l were associated with a higher incidence of subsequent malignant disease (P less than 0.05), the risk being at least nine times greater in these patients. The predictive value of high levels of SP1 was 35%, the specificity 45.8% and sensitivity 100%.