Progestin regulation of 11β-hydroxysteroid dehydrogenase expression in T-47D human breast cancer cells

This study examined the enzymatic characteristics and steroid regulation of the glucocorticoid-metabolizing enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) in the human breast cancer cell line T-47D. In cell homogenates, exogenous NAD significantly increased the conversion of corticosterone to 11-dehydrocorticosterone, while NADP was ineffective. There was no conversion of 11-dehydrocorticosterone to corticosterone either with NADH or NADPH demonstrating the lack of reductase activity. In keeping with these results, RT-PCR analysis indicated a mRNA for 11 beta-HSD2 in T-47D cells, while 11 beta-HSD1 mRNA levels were undetectable. In T-47D cells treated for 24 h with medroxyprogesterone acetate (MPA), 11 beta-HSD catalytic activity was elevated 11-ford, while estrone (E-1), estradiol (E-2) and the synthetic glucocorticoid dexamethasone (DEX) were ineffective. The antiprogestin mifepristone (RU486) acted as a pure antagonist of the progestin-enhanced Ile-HSD activity, but did not exert any agonistic effects of its own. In addition, RT-PCR analysis demonstrated that MPA was a potent inducer of 11 beta-HSD2 gene expression, increasing the steady-state levels of 11 beta-HSD2 mRNA. Taken together, these results demonstrate that 11 beta-HSD2 is the 11 beta-HSD isoform expressed by T-47D cells under steady-state conditions and suggest the existence of a previously undocumented mechanism of action of progestins in breast cancer cells. (C) 2000 Elsevier Science Ltd. All rights reserved.