The effect of transforming growth factor-beta on steroidogenesis and expression of key steroidogenic enzymes with a human ovarian thecal-like tumor cell model

Objective: Our purpose was to determine the effects of transforming growth factor-beta on steroidogenesis and regulation of steroidogenic enzyme expression by use of a human ovarian thecal-like tumor cell culture system. Study Design: Human ovarian thecal-like tumor cells were treated in serum-free medium in the presence or absence of forskolin and transforming growth factor beta(1). The accumulation of progesterone and androstenedione in the culture medium was evaluated by radioimmunoassay. The effects of forskolin with or without transforming growth factor-beta(1) on the enzymatic activity of P450c17 protein, and the expression of messenger ribonucleic acid for P450scc, P450c17, and 3betaHSD were determined. Results: Basal steroid secretion, steroidogenic enzyme activity, enzyme protein, and messenger ribonucleic acid expression were not affected by transforming growth factor-beta(1) alone. Forskolin treatment significantly stimulated steroid production and the enzymatic activity of P450c17 and 3betaHSD up to 10-fold above basal levels. However, transforming growth factor-beta(1) inhibited forskolin-stimulated androstenedione production to near basal levels and increased progesterone 1.4- to 2-fold while suppressing P450c17 enzyme activity to near basal levels, but it did not affect 3betaHSD activity. Forskolin-stimulated immunodetectable P450c17alpha protein was markedly inhibited by transforming growth factor-beta(1). In addition, transforming growth factor-beta(1) markedly inhibited the forskolin-stimulation of P450c17 messenger ribonucleic acid, while not significantly altering P450scc or 3betaHSD messenger ribonucleic acid expression. Conclusion: Forskolin stimulated human ovarian thecal-like tumor cell steroidogenesis, P450c17 and 3betaHSD activity, immunodetectable P450c17, and messenger ribonucleic acid content for P450scc, P450c17, and 3betaHSD. transforming growth factor-beta(1) inhibited forskolin stimulation of androstenedione production through the inhibition of P450c17 expression.