androstane-3-17-dione--(5alpha)-isomer and Breast-Neoplasms

Aldo-keto reductase (AKR) 1C3 (type 5 17beta-hydroxysteroid dehydrogenase and prostaglandin F synthase), may stimulate proliferation via steroid hormone and prostaglandin (PG) metabolism in the breast. Purified recombinant AKR1C3 reduces PGD(2) to 9alpha,11beta-PGF(2), Delta(4)-androstenedione to testosterone, progesterone to 20alpha-hydroxyprogesterone, and to a lesser extent, estrone to 17beta-estradiol. We established MCF-7 cells that stably express AKR1C3 (MCF-7-AKR1C3 cells) to model its over-expression in breast cancer. AKR1C3 expression increased steroid conversion by MCF-7 cells, leading to a pro-estrogenic state. Unexpectedly, estrone was reduced fastest by MCF-7-AKR1C3 cells when compared to other substrates at 0.1muM. MCF-7-AKR1C3 cells proliferated three times faster than parental cells in response to estrone and 17beta-estradiol. AKR1C3 therefore represents a potential target for attenuating estrogen receptor alpha induced proliferation. MCF-7-AKR1C3 cells also reduced PGD(2), limiting its dehydration to form PGJ(2) products. The AKR1C3 product was confirmed as 9alpha,11beta-PGF(2) and quantified with a stereospecific stable isotope dilution liquid chromatography-mass spectrometry method. This method will allow the examination of the role of AKR1C3 in endogenous prostaglandin formation in response to inflammatory stimuli. Expression of AKR1C3 reduced the anti-proliferative effects of PGD(2) on MCF-7 cells, suggesting that AKR1C3 limits peroxisome proliferator activated receptor gamma (PPARgamma) signaling by reducing formation of 15-deoxy-Delta(12,14)-PGJ(2) (15dPGJ(2)).

Topics: 20-alpha-Dihydroprogesterone; 3-Hydroxysteroid Dehydrogenases; 5-alpha-Dihydroprogesterone; Aldo-Keto Reductase Family 1 Member C3; Androstenedione; Androsterone; Biocatalysis; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Dihydrotestosterone; Dinoprost; Estradiol; Estrone; Etiocholanolone; Female; Gene Expression Regulation, Neoplastic; Gonadal Steroid Hormones; Humans; Hydroxyprostaglandin Dehydrogenases; Ketosteroids; Kinetics; Progesterone; Prostaglandin D2; Prostaglandins; Recombinant Proteins; Testosterone; Transfection; Up-Regulation

Steroid delta 4-5 alpha- and delta 4-5 beta-reductase activity was determined in 16 human mammary tumors and 8 DMBA-induced rat mammary tumors using a spectrophotometric assay. Steroid delta 4-5 alpha-reductase was present in all tumors investigated while delta 4-5 beta-reductase was detected in only 6 estrogen receptor negative human breast tumors and absent in all estrogen receptor positive human breast tumors as well as in all rat mammary tumors. Further support for the presence of delta 4-5 beta-reductase was established by using a dual-labelling technique consisting of incubating tumor slices with [14C] testosterone and adding [3H] etiocholanolone, [3H] testosterone and [3H]-5 alpha-dihydrotestosterone at the end of the reaction. Following extraction and chromic acid oxidation, 4-androstenedione, 5 beta-androstanedione and 5 alpha-androstanedione were isolated and purified, and the constancy of the 14C/3H ratio was used as proof of 5 alpha-reductase and 5 beta-reductase. These results were shown to be consistent with the data obtained using the spectrophotometric assay.

Topics: 3-Oxo-5-alpha-Steroid 4-Dehydrogenase; 9,10-Dimethyl-1,2-benzanthracene; Androstenedione; Animals; Breast Neoplasms; Dihydrotestosterone; Etiocholanolone; Female; History, 18th Century; Humans; Mammary Neoplasms, Experimental; Rats; Receptors, Estrogen; Stereoisomerism; Testosterone