In vitro and in vivo studies of the production of placental proteins (HCG, SP1, PPs) in human choriocarcinoma cell lines.

The production of human chorionic gonadotropin (hCG), pregnancy-specific beta-1 glycoprotein (SP1), and the various placental tissue proteins (PP4, PP5, PP10, PP11, PP12, MP1) was examined in human choriocarcinoma cell lines using radioimmunoassay (RIA) and an immunoperoxidase (PAP) staining method. In 6 gestational and 2 nongestational choriocarcinoma cell lines, hCG was produced in vitro. A significant heterogeneity of hCG production was noted among the cell lines. Production of hCG in the xenograft tumors was consistent with the hCG production of the same cell lines in vitro. SP1 was demonstrated both in the culture supernatants and the xenograft tumors of 3 cell lines, and the production was found to be inversely correlated with the hCG production of the cell lines. Positive staining for PP4 and MP1, and weakly positive staining for PP5, PP10, and PP12 was found in the xenograft tumors by immunoperoxidase (PAP) stain, but the staining for PP11 was negative. These placental proteins showed positive staining in portions of choriocarcinoma cells. These results indicate that placental proteins are not equally produced in heterogeneous choriocarcinoma cells.