Hormonal imbalance in breast cancer

Wide spectrum of steroids serving as substrates for the formation of lipoidal derivatives in ZR-75-1 human breast cancer cells

Recently, several natural steroids have been found to be esterified to long-chain fatty acids (FAE) in various mammalian tissues. The purpose of the present study was to determine the ability of a series of 3H-labeled steroids to serve as substrates for the formation and accumulation of such non-polar derivatives in intact cells, using the hormone-responsive ZR-75-1 human breast cancer cell line as model. All 14 steroids tested were found to be converted, directly or following further metabolism, to lipoidal ester derivatives. The percentage of intracellular steroids recovered as FAE derivatives was usually substantial (14-90%), especially in the case of C-19 steroids (75-90%). The composition of the lipoidal steroid fractions recovered from the labeled cell extracts was characterized by chromatographic comparison with synthetic steroid FAEs and by saponification of the steroid FAEs and identification of the released steroidal moieties. Following metabolism, most steroid substrates were converted into multiple lipoidal esters. Furthermore, 5 alpha-androstane-3 alpha, 17 beta-diol, 5 alpha-androstane-3 beta, 17 beta-diol, as well as androst-5-ene-3 beta, 17 beta-diol formed lipoidal diesters in addition to the monoester form. The high level of intracellular steroid FAE accumulation reported in this study suggests that these yet poorly known steroid derivatives may play important functions in the regulation of steroid hormone metabolism and action.

Metabolism of pregnenolone by human breast cancer. Evidence for 17 alpha-hydroxylase and 17,20-lyase

The metabolism of 7-(3)H-pregnenolone was studied in vitro using 16 human breast carcinomas. All mammary tumors transformed pregnenolone to progesterone. All estrogen receptor poor tumors and 4 out of 8 estrogen receptor rich tumors converted pregnenolone to 17-hydroxypregnenolone. Five estrogen receptor poor tumors showed the presence of 17,20-lyase as evidenced by formation of dehydroepiandrosterone and androstenedione. In two estrogen receptor poor tumors, conversions of pregnenolone to progesterone, 17-hydroxy pregnenolone, dehydroepiandrosterone, androstenedione and finally to estradiol was documented, providing a hypothetical pathway for steroid metabolism in human breast cancer. The conversion of pregnenolone to 17-hydroxypregnenolone was significantly less in receptor rich tumors and was totally absent in 4 receptor rich tumors with estrogen receptors of over 45 fmol/mg protein.

Therapy of dimethylbenzanthracene-induced mammary carcinomas in the rat by selective inhibition of steroidogenesis

The effects of cyanoketone, a specific inhibitor of steroidogenesis at the levels of 3beta-hydroxysteroid oxidoreductase-dealta54-3-ketosteroid isomerase, the combination of cyanoketone with corticosterone, and corticosterone alone on the growth of dimethylbenzanthracene-induced hormone-dependent breast cancers in rats were compared with that produced by ovariectomy. Cyanoketone produces about as many regresssions of these cancers as does ovariectomy. However, cyanoketone with corticosterone results in a significant regression of tumors in all animals tested. This therapy also causes regression of significantly more tumors that are large at the beginning of treatment than does ovariectomy. These findings suggest that this kind of reversible blockade of steroidogenesis may be useful as a diagnostic tool in assessing the hormone dependence of breast tumors and as a possible therapeutic approach in the treatment of such tumors.