Progestin induction of 17β‐hydroxysteroid dehydrogenase enzyme protein in the t‐47D human breast‐cancer cell line

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Abstract
Steroid regulation of 17β‐hydroxysteroid dehydrogenase (17‐HSD) was studied in the T‐47D human breast‐cancer cell line, using a radioimmunoassay. In addition, 3 mRNA species (2.4, 1.4, and 0.9 kb) specific for the enzyme were shown to be present in these cells. All the synthetic progestins tested (ORG 2058, R5020, medroxyprogesterone acetate) significantly increased the immunoreactive enzyme protein concentration, while other types of steroids, such as testosterone, oestradiol and dexamethasone, were ineffective. The progestin‐specific induction of 17‐HSD was dose‐related and was maximum in about 5 days. An antiprogestin, RU 486, when used in combination with synthetic progestins, blocked the progestin‐induced increase of 17‐HSD concentration very effectively. A good correlation was observed in the different experiments between the enzyme activity and the immunoreactive 17‐HSD concentration. We conclude that progestins induce 17‐HSD in T‐47D cells and that the induction occurs via an increased accumulation of enzyme protein.
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