| Abstract: | 17β-hydroxysteroid dehydrogenase (17HSD) type 1 converts the weakly active estrogen, estrone, into highly active estradiol. In addition to being essential for gonadal estradiol biosynthesis, the enzyme is also expressed in a significant proportion of breast tumors. In order to study the role of the enzyme in estrogen-dependent growth of breast cancer, MCF-7 breast-cancer cells stably expressing human 17HSD type 1 were generated. In control MCF-7 cells a very low 17HSD activity was observed and, in line with its low estrogenic activity, estrone was devoid of the growth-enhancing effect of estradiol. The presence of the enzyme in the stably transfected HSD-7 cells resulted in a rapid conversion of estrone into estradiol but did not alter the estrogen-receptor concentration in the cells. However, in transfected cells, estrone had a growth-promoting effect practically identical to that of estradiol. The presence or absence of 17HSD type 1 in breast-cancer cells may therefore be decisive with regard to estrogen exposure and the estrogen-responsive growth of breast-cancer tissues. © 1996 Wiley-Liss, Inc. |
