Immunologic and physical characterization of human chorionic gonadotropin and its subunits in cultures of human malignant trophoblast.

Culture fluids and cell homogenates from cultures of BeWo human malignant trophoblast cells were examined for the presence of chorionic gonadotropin (hCG) and its subunits by gel filtration on a calibrated Sephadex G-200 column. Culture fluids, cell homogenates, and gel filtration eluates were radioimmunoassayed in homologous hCG, hCGα, and hCGβ assays. The gel filtration pattern from the culture fluid consisted of 3 discrete antigenie peaks, including hCG and hCGβ of normal size and hCGα of apparently larger than normal size. There was approximately twice as much hCG as hCGβ or hCGα in the culture fluid. The gel filtration profile from the cell homogenate consisted mainly of a broad peak of hCGβ but only small amounts of hCG and hCGα. The major hCGβ and hCGα peaks were of apparently smaller molecular weight than highly purified hCGβ and hCGα standards, respectively. The dose-response behavior of trophoblast cell homogenate in the homologous radioimmunoassays for hCG, hCGα, and hCGβ provided additional ev...