Establishment of clonal human placental cells synthesizing human choriogonadotropin

Seven clonal human placental cell lines were established by transformation of human first-trimester placental cells with simian virus 40. These transformed cells synthesized native human choriogonadotropin (chorionic gonadotropin) (hCG) as well as the free alpha and beta subunits of hCG. The amount of native hCG synthesized by these cells was, however, lower than the amount of free beta subunit. (Both hCG and the beta subunit are detected by the radioimmunoassay for beta subunit, but only hCG is detected by the radioreceptor assay.) The alpha and beta subunits produced by these transformed placental cells were heterogeneous in size; the sizes of the predominant alpha and beta species, however, corresponded to those of urinary alpha and beta subunits, respectively. The seven cell lines transformed by simian virus 40 had chromosome numbers from the near diploid to the near tetraploid range. Fluorescent staining demonstrated the Y chromosome in all the transformants. Furthermore, B-type glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate: NADP+ 1-oxidoreductase; EC 1.1.1.49) was present in all seven lines. These characteristics ruled out possible HeLa contamination of the transformed lines. Regulation of the synthesis of alpha and beta subunits plus hCG in these transformed human placental cells differed from the regulation in choriocarcinoma cells.