Properties and regulation of 17 beta-hydroxysteroid oxidoreductase of OVCAR-3, CAOV-3, and A431 cells: effects of epidermal growth factor, estradiol, and progesterone.

Although there is a growing body of evidence that 17 beta-hydroxysteroid oxidoreductase plays a role in the regulation of steroid levels in epithelial tumors of the endometrium and breast, our knowledge of its role in other gynecologic tumors is limited. In this investigation, the 17 beta-hydroxysteroid oxidoreductase activity of cell lines derived from two ovarian tumors (OVCAR-3, CAOV-3) and an epidermoid tumor of the vulva (A431) was assayed under conditions which differentiate between 17 beta-hydroxysteroid oxidoreductase type 1, a cytosolic isoform highly specific for estradiol, and type 2, a membrane bound isoform reactive with both estradiol and testosterone. On the basis of estradiol/testosterone activity ratios, all three cell lines appear to have type 2-like activity, with the specific activity of A431 markedly greater than that of the other cell lines. Estradiol, progesterone, or EGF, alone or in combination, were without effect on the enzymatic activity of OVCAR-3 cells. EGF decreased the activity of CAOV-3 cells slightly. In contrast, EGF stimulated A431 17 beta-hydroxysteroid oxidoreductase activity 7-8-fold over a 5-day exposure. Estradiol or progesterone, singly or in combination, also did not effect the enzymatic activity of A431 cells. However, progesterone inhibited the increase in activity seen in the presence of EGF. With EGF, estradiol, and progesterone together, the increase in enzymatic activity was comparable to that with EGF alone. The effects of estradiol and progesterone appear to result from steroid actions following binding of EGF to low-affinity receptors on A431 cells.