Fibroblast growth factor enhances human chorionic gonadotropin synthesis independent of mitogenic stimulation in jar choriocarcinoma cells

The Jar choriocarcinoma cell line was used as an in vitro placental cell model to determine the effects of polypeptide growth factors on hCGβ secretion. Epidermal and fibroblast growth factor (FGF) treatment of serum-free cultures stimulated hCGβ secretion 2.5- and 4.0-fold over basal serumfree control levels within a 15-h incubation period. Insulin-like growth factor I, nerve growth factor, and transforming growth factor-β had no significant effect on hCGβ secretion. FGF at concentrations as low as 0.125 ng/ml significantly elevated medium hCGβ levels without increasing cell number or total cellular protein. FGF stimulation of secretion was not detectable until 2 h of treatment. Intracellular hCGβ remained constant (23%) relative to total hCGβ (cell plus medium) as total hCGβ increased 3-fold, suggesting that FGF stimulated de nouo hCGβ synthesis. Insulin significantly augmented the FGF-induced hCGβ stimulation without stimulating hCGβ production itself.