Ectopic production of "pregnancy-specific" beta-1 glycoprotein in vitro: discordance with three other placental proteins.

"Pregnancy-specific" beta-1 glycoprotein (SP1) was produced in vitro by nine of 32 established cell lines derived from human malignant neoplasms. The nine positive lines comprised a variety of cell types, and SP1 production ranged from 0.36 to 35.5 pmol/mg cell protein at confluence. The highest production was by a fibrosarcoma line. SP1 in medium and cells from this line was indistinguishable immunochemically and gel chromatographically from purified (Bohn) placental SP1. None of the SP1-positive lines produced placental lactogen, only three produced the alpha subunit of chorionic gonadotropin (CG), and only four produced the beta subunit of CG. SP1-positive lines that produced cg-alpha did not produce CG-beta. Secretion of SP1 and of CG-beta by the fibrosarcoma line followed different time courses.