Multiple steroid metabolic pathways in ZR-75-1 human breast cancer cells

Patterns of chemical diversity in the marine ascidian Phallusia spp.: anti-tumor activity and metabolic pathway inhibiting steroid biosynthesis

The complex nature of marine biodiversity is partially responsible for the lack of studies in Indian ascidian species, which often target a small number of novel biomolecules. We performed untargeted metabolomics using gas chromatography-mass spectrometry (GC-MS) in two invasive ascidian species to investigate the inter-specific chemical diversity of Phallusia nigra and P. arabica in search of drug-like properties and metabolic pathways. The chemical profiling of individual ascidian species was obtained using GC-MS, and the metabolites were determined by searching in NIST library and literature data. The principal component analysis of GC-MS mass spectral variables showed a clear discrimination of these two ascidian species based on the chemical composition and taxonomy. The metabolites, lipids, macrolides, and steroids contributed strongly to the discrimination of these two species. Results of this study confirmed that GC-MS-based chemical profiling could be utilized as a tool for chemotaxonomic classification of ascidian species. The extract of P. nigra showed promising anti-tumor activity against HT29 colon cancer 35 µM and MCF7-breast cancer (34.76 µM) cells compared to P. arabica. Of the more than 70 metabolites measured, 18 metabolites that mapped various pathways linked to three metabolic pathways being impacted and altered in steroid biosynthesis, primary bile acid biosynthesis, and steroid hormone biosynthesis were observed to have changed significantly (p > 0.004, FDR < 0.01). Also, higher expression of this pathway was associated with more significant cytotoxicity in breast and colon carcinoma cells.

Evaluation of Active Hexose Correlated Compound (AHCC) in Combination With Anticancer Hormones in Orthotopic Breast Cancer Models

Objective. To determine the impact on antitumor activity when active hexose correlated compound (AHCC) in combination with anticancer hormonal agents in orthotopic mouse models of human estrogen receptor positive breast cancer and evaluate impact of AHCC on aromatase activity. Methods. The study consisted of 7 treatment arms (n=10) conducted in 2 breast cancer mouse models: MCF-7 and ZR-75. Treatment groups included untreated, vehicle, AHCC 50 mg/kg, AHCC 50 mg/kg + tamoxifen 10 mg/kg, tamoxifen 10 mg/kg, AHCC 50 mg/kg + letrozole 10 µg/mouse, or letrozole 10 µg/mouse. All treatments were administered daily by oral gavage for 12 weeks. Tumors were measured 3 times a week. In vitro estrone and 17β-estradiol enzyme immunoassay was used to evaluate aromatase activity. Results. There was no difference in the activity with the combination of AHCC + tamoxifen compared with tamoxifen (P = 0.29). In the ZR-75 model (catechol-O-methyltransferase [COMT] wild-type), there was no difference in activity with the letrozole + AHCC compared with letrozole. However, in the MCF-7 model (COMT variant), AHCC + letrozole resulted in a decrease in activity compared with letrozole (P < 0.01). Immunoassay data suggested that AHCC is a potential inducer of aromatase activity. In both tumor models, there was cytotoxicity observed with AHCC compared with untreated (P < 0.02). Conclusion. AHCC did not change the activity of tamoxifen. AHCC may have some interaction with letrozole in patients with COMT variant genotype. AHCC had cytotoxicity that warrents additional studies to evaluate its potential role for consolidation/prevention of breast cancer.

Anti-tumor effect of Shu-Gan-Liang-Xue decoction in breast cancer is related to the inhibition of aromatase and steroid sulfatase expression

ETHNOPHARMACOLOGICAL RELEVANCE

Shu-Gan-Liang-Xue Decoction (SGLXD), a traditional Chinese herbal formula used to ameliorate the hot flushes in breast cancer patients, was reported to have anti-tumor effect on breast cancer. Estrogen plays a critical role in the genesis and evolution of breast cancer. Aromatase and steroid sulfatase (STS) are key estrogen synthesis enzymes that predominantly contribute to the high local hormone concentrations. The present study was to evaluate the anti-tumor effect of SGLXD on estrogen receptor (ER) positive breast cancer cell line ZR-75-1, and to investigate its underlying mechanisms both in vitro and in vivo.

MATERIALS AND METHODS

The anti-tumor activity of SGLXD in vitro was investigated using the MTT assay. The in vivo anti-tumor effect of SGLXD was evaluated in non-ovariectomized and ovariectomized athymic nude mice. The effect of SGLXD on enzymatic activity of aromatase and STS was examined using the dual-luciferase reporter (DLR) based on bioluminescent measurements. Aromatase and STS protein level were assessed using Western blot assay.

RESULTS

SGLXD showed dose-dependent inhibitory effect on the proliferation of ZR-75-1 cells with IC50 value of 3.40 mg/mL. It also suppressed the stimulating effect on cell proliferation of testosterone and estrogen sulfates (E1S). Oral administration of 6 g/kg of SGLXD for 25 days resulted in a reduction in tumor volume in non-ovariectomized and ovariectomized nude mice. The bioluminescent measurements confirmed that SGLXD has a dual-inhibitory effect on the activity of aromatase and STS. Western blot assay demonstrated that the treatment of SGLXD resulted in a decrease in aromatase and STS protein levels both in vitro and in vivo.

CONCLUSION

Our results suggested that SGLXD showed anti-tumor effect on breast cancer cells both in vitro and in vivo. The anti-tumor activity of SGLXD is related to inhibition of aromatase and STS via decreasing their expression. SGLXD may be considered as a novel treatment for ER positive breast cancer.

Differential effects of exogenous androgen and an androgen receptor antagonist in the peri- and postpubertal murine mammary gland

There is emerging evidence that androgens inhibit proliferation of normal and malignant breast epithelial cells, but the actions of androgens in normal mammary gland morphogenesis are not well understood. In this study, we investigated whether development of the murine mammary gland could be altered by stimulating or suppressing androgen receptor (AR) signaling in vivo. Intact virgin female mice aged 5 wk (midpuberty) or 12 wk (postpuberty) were implanted with slow-release pellets containing either placebo, 5α-dihydrotestosterone (1.5 mg) or the AR antagonist flutamide (60 mg). Treatment with 5α-dihydrotestosterone from midpuberty to 12 wk of age-retarded ductal extension by 40% (P = 0.007), but treatment from 12-21 wk had no significant effect on gland morphology. In contrast, inhibition of AR signaling with flutamide from midpuberty had no effect on the mammary gland, but flutamide treatment from 12-21 wk increased ductal branching (P = 0.004) and proliferation (P = 0.03) of breast epithelial cells. The increased proliferation in flutamide-treated mice was not correlated with serum estradiol levels or estrogen receptor-α (ERα) expression. In control mice, the frequency and intensity of AR immunostaining in mammary epithelial cells was significantly increased in the 12- to 21-wk treatment group compared with the 5- to 12-wk group (P < 0.001). In contrast, no change in ERα occurred, resulting in a marked increase in the AR to ERα ratio from 0.56 (±0.12) to 1.47 (±0.10). Our findings indicate that androgen signaling influences development and structure of the adult mammary gland and that homeostasis between estrogen and androgen signaling in mature glands is critical to constrain the proliferative effects of estradiol.

Selective insensitivity of ZR-75-1 human breast cancer cells to 2-methoxyestradiol: evidence for type II 17beta-hydroxysteroid dehydrogenase as the underlying cause

2-Methoxyestradiol (2-MeO-E2), a nonpolar endogenous metabolite of 17beta-estradiol, has strong antiproliferative, apoptotic, and antiangiogenic actions. Among the four human breast cancer cell lines tested (MCF-7, T-47D, ZR-75-1, and MDA-MB-435s), the ZR-75-1 cells were selectively insensitive to the antiproliferative actions of 2-MeO-E2, although these cells had a similar sensitivity as other cell lines to several other anticancer agents (5-fluorouracil, mitomycin C, doxorubicin, colchicine, vinorelbine, and paclitaxel). Mechanistically, this insensitivity is largely attributable to the presence of high levels of a steroid-selective metabolizing enzyme, the type II 17beta-hydroxysteroid dehydrogenase (17beta-HSD), in the ZR-75-1 cells, which rapidly converts 2-MeO-E2 to the inactive 2-methoxyestrone, but this enzyme does not metabolically inactivate other nonsteroidal anticancer agents. The type II 17beta-HSD-mediated conversion of 2-MeO-E2 to 2-methoxyestrone in ZR-75-1 cells followed the first-order kinetics, with a very short half-life (approximately 2 hours). In comparison, the T-47D, MCF-7, and MDA-MB-435s human breast cancer cells, which were highly sensitive to 2-MeO-E2, had very low or undetectable catalytic activity for the conversion of 2-MeO-E2 to 2-methoxyestrone. Reverse transcription-PCR analysis of the mRNA levels of three known oxidative 17beta-HSD isozymes (types II, IV, and VIII) revealed that only the type II isozyme was selectively expressed in the ZR-75-1 cells, whereas the other two isozymes were expressed in all four cell lines. Taken together, our results showed, for the first time, that the high levels of type II 17beta-HSD present in ZR-75-1 cells were largely responsible for the facile conversion of 2-MeO-E2 to 2-methoxyestrone and also for the selective insensitivity to the antiproliferative actions of 2-MeO-E2.

Molecular biology of the 3beta-hydroxysteroid dehydrogenase/delta5-delta4 isomerase gene family

The 3beta-hydroxysteroid dehydrogenase/Delta(5)-Delta(4) isomerase (3beta-HSD) isoenzymes are responsible for the oxidation and isomerization of Delta(5)-3beta-hydroxysteroid precursors into Delta(4)-ketosteroids, thus catalyzing an essential step in the formation of all classes of active steroid hormones. In humans, expression of the type I isoenzyme accounts for the 3beta-HSD activity found in placenta and peripheral tissues, whereas the type II 3beta-HSD isoenzyme is predominantly expressed in the adrenal gland, ovary, and testis, and its deficiency is responsible for a rare form of congenital adrenal hyperplasia. Phylogeny analyses of the 3beta-HSD gene family strongly suggest that the need for different 3beta-HSD genes occurred very late in mammals, with subsequent evolution in a similar manner in other lineages. Therefore, to a large extent, the 3beta-HSD gene family should have evolved to facilitate differential patterns of tissue- and cell-specific expression and regulation involving multiple signal transduction pathways, which are activated by several growth factors, steroids, and cytokines. Recent studies indicate that HSD3B2 gene regulation involves the orphan nuclear receptors steroidogenic factor-1 and dosage-sensitive sex reversal adrenal hypoplasia congenita critical region on the X chromosome gene 1 (DAX-1). Other findings suggest a potential regulatory role for STAT5 and STAT6 in transcriptional activation of HSD3B2 promoter. It was shown that epidermal growth factor (EGF) requires intact STAT5; on the other hand IL-4 induces HSD3B1 gene expression, along with IL-13, through STAT 6 activation. However, evidence suggests that multiple signal transduction pathways are involved in IL-4 mediated HSD3B1 gene expression. Indeed, a better understanding of the transcriptional factors responsible for the fine control of 3beta-HSD gene expression may provide insight into mechanisms involved in the functional cooperation between STATs and nuclear receptors as well as their potential interaction with other signaling transduction pathways such as GATA proteins. Finally, the elucidation of the molecular basis of 3beta-HSD deficiency has highlighted the fact that mutations in the HSD3B2 gene can result in a wide spectrum of molecular repercussions, which are associated with the different phenotypic manifestations of classical 3beta-HSD deficiency and also provide valuable information concerning the structure-function relationships of the 3beta-HSD superfamily. Furthermore, several recent studies using type I and type II purified enzymes have elegantly further characterized structure-function relationships responsible for kinetic differences and coenzyme specificity.

Activity and expression of progesterone metabolizing 5alpha-reductase, 20alpha-hydroxysteroid oxidoreductase and 3alpha(beta)-hydroxysteroid oxidoreductases in tumorigenic (MCF-7, MDA-MB-231, T-47D) and nontumorigenic (MCF-10A) human breast cancer cells

BACKGROUND

Recent observations indicate that human tumorous breast tissue metabolizes progesterone differently than nontumorous breast tissue. Specifically, 5alpha-reduced metabolites (5alpha-pregnanes, shown to stimulate cell proliferation and detachment) are produced at a significantly higher rate in tumorous tissue, indicating increased 5alpha-reductase (5alphaR) activity. Conversely, the activities of 3alpha-hydroxysteroid oxidoreductase (3alpha-HSO) and 20alpha-HSO enzymes appeared to be higher in normal tissues. The elevated conversion to 5alpha-pregnanes occurred regardless of estrogen (ER) or progesterone (PR) receptor levels. To gain insight into these differences, the activities and expression of these progesterone converting enzymes were investigated in a nontumorigenic cell line, MCF-10A (ER- and PR-negative), and the three tumorigenic cell lines, MDA-MB-231 (ER- and PR-negative), MCF-7 and T-47D (ER- and PR-positive).

METHODS

For the enzyme activity studies, either whole cells were incubated with [14C]progesterone for 2, 4, 8, and 24 hours, or the microsomal/cytosolic fraction was incubated for 15-60 minutes with [3H]progesterone, and the metabolites were identified and quantified. Semi-quantitative RT-PCR was employed to determine the relative levels of expression of 5alphaR type1 (SRD5A1), 5alphaR type 2 (SRD5A2), 20alpha-HSO (AKR1C1), 3alpha-HSO type 2 (AKR1C3), 3alpha-HSO type 3 (AKR1C2) and 3beta-HSO (HSD3B1/HSD3B2) in the four cell lines using 18S rRNA as an internal control.

RESULTS

The relative 5alpha-reductase activity, when considered as a ratio of 5alpha-pregnanes/4-pregnenes, was 4.21 (+/- 0.49) for MCF-7 cells, 6.24 (+/- 1.14) for MDA-MB-231 cells, 4.62 (+/- 0.43) for T-47D cells and 0.65 (+/- 0.07) for MCF-10A cells, constituting approximately 6.5-fold, 9.6-fold and 7.1 fold higher conversion to 5alpha-pregnanes in the tumorigenic cells, respectively, than in the nontumorigenic MCF-10A cells. Conversely, the 20alpha-HSO and 3alpha-HSO activities were significantly higher (p < 0.001) in MCF-10A cells than in the other three cell types. In the MCF-10A cells, 20alpha-HSO activity was 8-14-fold higher and the 3alpha-HSO activity was 2.5-5.4-fold higher than in the other three cell types. The values of 5alphaR:20alpha-HSO ratios were 16.9-32.6-fold greater and the 5alphaR:3alpha-HSO ratios were 5.2-10.5-fold greater in MCF-7, MDA-MB-231 and T-47D cells than in MCF-10A cells. RT-PCR showed significantly higher expression of 5alphaR1 (p < 0.001), and lower expression of 20alpha-HSO (p < 0.001), 3alpha-HSO2 (p < 0.001), 3alpha-HSO3 (p < 0.001) in MCF-7, MDA-MB-231 and T-47D cells than in MCF-10A cells.

CONCLUSION

The findings provide the first evidence that the 5alphaR activity (leading to the conversion of progesterone to the cancer promoting 5alpha-pregnanes) is significantly higher in the tumorigenic MCF-7, MDA-MB-231 and T-47D breast cell lines than in the nontumorigenic MCF-10A cell line. The higher 5alphaR activity coincides with significantly greater expression of 5alphaR1. On the other hand, the activities of 20alpha-HSO and 3alpha-HSO are higher in the MCF-10A cells than in MCF-7, MDA-MB-231 and T-47D cells; these differences in activity correlate with significantly higher expression of 20alpha-HSO, 3alpha-HSO2 and 3alpha-HSO3 in MCF-10A cells. Changes in progesterone metabolizing enzyme expression (resulting in enzyme activity changes) may be responsible for stimulating breast cancer by increased production of tumor-promoting 5alpha-pregnanes and decreased production of anti-cancer 20alpha--and 3alpha-4-pregnenes.

Analysis and characteristics of multiple types of human 17beta-hydroxysteroid dehydrogenase

Androgens and estrogens are not only synthesized in the gonads but also in peripheral target tissues. Accordingly, recent molecular cloning has allowed us to identify multiple types of 17beta-hydroxysteroid dehydrogenases (17beta-HSD), the key and exclusive enzymes involved in the formation and inactivation of sex steroids. However, only one form, namely, type 3 17beta-HSD, is responsible for pseudohermaphroditism in deficient boys. To date, seven human 17beta-HSDs have been isolated and characterized. Although they catalyze substrates having a similar structure, 17beta-HSDs have very low homology. In intact cells in culture, these enzymes catalyze the reaction in a unidirectional way - types 1, 3, 5 and 7 catalyze the reductive reaction, while types 2, 4 and 8 catalyze the oxidative reaction. It is noteworthy that rat type 6 17beta-HSD also catalyzes the reaction in the oxidative direction. In this report, we analyze the different characteristics of the multiple types of human 17beta-HSD.

Androgen formation and metabolism in the pulmonary epithelial cell line A549: expression of 17beta-hydroxysteroid dehydrogenase type 5 and 3alpha-hydroxysteroid dehydrogenase type 3

Surfactant synthesis within developing fetal lung type II cells is affected by testosterone and 5alpha-dihydrotestosterone (5alpha-DHT). The pulmonary epithelial cell line A549, isolated from a human lung carcinoma, like normal lung type II cell, produces disaturated phosphatidylcholines and has been widely used for studying the regulation of surfactant production. Androgen receptor has been detected in A549 cells; however, the capacity of these cells for androgen synthesis and metabolism has not been investigated at molecular level. This study was undertaken to identify the steroidogenic enzymes involved in the formation and metabolism of androgens from adrenal C19 steroid precursors in A549 cells. When cultured in the presence of normal FCS, A549 intact cells converted DHEA to androstenediol, androstenedione principally to testosterone, and 5alpha-DHT to 5alpha-androstane 3alpha,17beta-diol. High levels of 17beta-hydroxysteroid dehydrogenase (HSD) and 3alpha-HSD activities were detected in both cytosol and microsomes isolated from homogenates. Analysis of A549 RNA indicated the presence of 17beta-HSD type 4 and type 5, and of 3alpha-HSD type 3 messenger RNAs. Very low levels of 3beta-HSD type 1 and 5alpha-reductase type 1 messenger RNAs and activities were detected. With regard to active androgen formation, there was little or no capacity for the conversion of DHEA to 5alpha-DHT. In contrast, androstenedione was rapidly transformed to testosterone. The pattern of steroid metabolism was not affected by the use of charcoal-stripped FCS or by the synthetic glucocorticoid dexamethasone. Together, our findings show that A549 cells express a pattern of steroid metabolism in which 17beta-HSD type 5 and 3alpha-HSD type 3 are the predominant enzymes. The level of androgens is regulated at the level of catalysis in intact cells such that the intracellular level of testosterone is stabilized, whereas 5alpha-DHT is rapidly inactivated by reduction to 3alpha,17beta-diol. This pattern of androgen metabolism has implications for the relative importance of testosterone and 5alpha-DHT in normal lung development and surfactant production.

Synthesis and evaluation of estradiol derivatives with 16 alpha-(bromoalkylamide), 16 alpha-(bromoalkyl) or 16 alpha-(bromoalkynyl) side chain as inhibitors of 17 beta-hydroxysteroid dehydrogenase type 1 without estrogenic activity

To develop inhibitors of 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) without residual estrogenic activity, the synthesis of 16 alpha-(bromoalkylamide) derivatives of estradiol was performed starting from a key intermediate aldehyde obtained from commercially available estrone. In addition, series of 16 alpha-(bromoalkyl) and 16 alpha-(bromoalkynyl) derivatives of estradiol were also prepared as model compounds. All new compounds inhibited human placental cytosolic 17 beta-HSD (type 1) with IC50 values ranging from 1.7 to 10.6 microM. From these results, we observed that a primary bromide produces a greater inhibition of 17 beta-HSD activity than secondary bromide, and that a shorter 16 alpha-side chain increases the inhibiting activity. In the estrogen-sensitive ZR-75-1 human breast cancer cell line, the 16 alpha-(bromoalkylamide)-estradiol series had no estrogenic activity at 30 nM, and only the compound with a shorter side chain length showed an estrogenic activity at 1000 nM. Interestingly, at this concentration, the compound with an intermediate side chain length showed an antiestrogenic activity of 74%, whereas the compound with the longer side chain length showed 34% of antiestrogenic activity. In this test, other 17 beta-HSD inhibitors (without bromoalkylamide side chain) were fully estrogenic. Among synthesized compounds, the estradiol derivative 4 (N-butyl, N-methyl, 9-[3',17' beta-(dihydroxy)-1',3',5'(10')-estratrien-16' alpha-yl]-7-bromononamide) was the best compromise for a dual-action inhibitor. This compound inhibited moderately and reversibly the 17 beta-HSD type 1 activity, but possessed no estrogenic activity and exhibited antiestrogenic activity in the ZR-75-1 cell line.

Isolation and characterization of a stereospecific 3beta-hydroxysteriod sulfotransferase (pregnenolone sulfotransferase) cDNA

In contrast to humans, who possess a hydroxysteroid sulfotransferase (HSST), namely, DHEA sulfotransferase (DHEA-ST), that displays broad substrate specificities, HSSTs of the guinea pig show a high substrate stereoselectivity, as shown by the recent cloning of a chiral-specific 3alpha-hydroxysteroid sulfotransferase. Herein, we report the cloning and expression of the substrate and chiral-specific pregnenolone sulfotransferase (PREG-ST). Transfection of the pCMV expression vector containing PREG-ST cDNA in transformed human embryonal kidney (293) cells showed that the expressed enzyme selectively catalyzes the 3beta-hydroxysteroid substrate. It converts pregnenolone to pregnenolone sulfate most efficiently, whereas dehydroepiandrosterone and epiandrosterone were transformed at a much lower rate, and androsterone, a 3alpha-hydroxysteroid, was not significantly metabolized (30-fold lower). Thus, the enzyme was identified as pregnenolone sulfotransferase. DNA analysis predicts a protein of 287 amino acids with a calculated molecular mass of 34,199 daltons. Alignment of the amino acid sequence with other sulfotransferases indicated that guinea pig pregnenolone sulfotransferase shares 75 and 80% homology with human DHEA sulfotransferase and rat hydroxysteroid dehydrogenase, respectively. RNA blot analysis using guinea pig liver, intestine, adrenal, kidney, epididymis, testis, and lung showed a single RNA species at 1.3 kb is expressed in liver, intestine, and kidney. Guinea pig 3beta-hydroxysteroid sulfotransferase is thus different from that in humans, who possess two mRNA species of 1.3 and 1.8 kb.

Characteristics of human types 1, 2 and 3 17 beta-hydroxysteroid dehydrogenase activities: oxidation/reduction and inhibition

Following transfection of types 1, 2 and 3 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) cDNAs into transformed embryonal kidney (293) cells, we have characterized the selective directional and inhibitory characteristics of these activities. While homogenates of transfected cells could catalyze interconversion of the substrate and product, in agreement with the general belief on the activity of these enzymes, the same activities measured in intact cells, in order to better reflect the physiological conditions, showed an unidirectional reaction. Types 1 and 3 17 beta-HSD catalyzed the reduction of estrone to estradiol and 4-androstenedione to testosterone, respectively, while type 2 17 beta-HSD catalyzed the oxidative transformation of both testosterone and 17 beta-estradiol to 4-androstenedione and estrone, respectively. In addition, types 1, 2 and 3 17 beta-HSD activities showed different pH optima. While types 1 and 3 showed pH optimum values centered at around 5 and 6, respectively, type 2 17 beta-HSD activity, which preferentially, catalyzes the oxidation reaction, has higher activity at an alkaline pH (8-10). Differences in the optimum incubation temperatures were also observed: type 1 17 beta-HSD shows a relatively high temperature tolerance (55 degrees C). In contrast, type 2 and 3 functioned best at 37 degrees C. Types 1, 2 and 3 17 beta-HSD activities could be also differentiated by their sensitivity toward various specific inhibitors: type 1 was potently inhibited by an estradiol derivative containing a bromo/or iodopropyl group at position 16 alpha. On the other hand a derivative of estrone containing a spiro-gamma-lactone at position 17 showed a potent inhibitory effect on type 2 17 beta-HSD, whereas type 3 was strongly inhibited by 1,4-androstadiene-1,6,17- trione.

Specific imaging of hormone-dependent mammary carcinoma in nude mice with [131I]-anti-estriol 3-sulfate antibody

We tried to put the estrogen metabolite to use in tumor imaging. The antibody against estriol 3-sulfate (E3 3-S), which was one of the major metabolites of estrogen in hormone-dependent mammary carcinoma, was prepared and the tissue distribution and imaging of human breast carcinoma with anti-E3 3-S antibody (Ab) were studied in nude mice. In hormone-dependent breast carcinoma, MCF-7,-bearing nude mice, [125I] anti-E3 3-S Ab localized in tumor with the percentage injected dose/g of 9.29 +/- 3.01 (mean +/- SD). This value was significantly high compared with that in hormone-independent breast carcinoma, MDA-MB-231,-bearing nude mice. At 72 h after the administration of [125I]anti-E3 3-S Ab to MCF-7 bearing mice, tumor/blood, tumor/liver and tumor/muscle ratios were 0.49, 5.02 and 6.83, respectively. These ratios were supposed to be enough for imaging. In radioimmunoscintigraphy, a MCF-7 tumor was clearly visualized at 120 or 168 h post-injection of [131I]anti-E3 3-S Ab.

Structural characterization and expression of the human dehydroepiandrosterone sulfotransferase gene

Dehydroepiandrosterone sulfotransferase catalyzes the transformation of dehydroepiandrosterone to dehydroepiandrosterone sulfate, the most abundant steroid in circulation in the human and primate. Dehydroepiandrosterone sulfate serves as precursor for the formation of active androgens and estrogens in peripheral target tissues. In addition, blockade at the dehydroepiandrosterone level could give raise to high level of DHEA and thus disorders due to mild excess of androgen. Recently, the cDNA encoding dehydroepiandrosterone sulfotransferase has been isolated from a human liver cDNA library. To study the regulation and expression, as well as the possible defect linked to DHEA sulfotransferase gene, we have isolated and characterized its structure by screening a lambda EMBL3 library of human leukocyte genomic DNA using human dehydroepiandrosterone sulfotransferase cDNA as a probe. Sequencing of the gene shows that it is included in approximately 17 kb and contains six exons separated by five introns. Northern blot analysis shows a strong signal in the adrenals and liver, whereas no signal was detected in the spleen, thymus, prostate, testis, ovary, small intestine, colon, peripheral blood leukocytes, heart, brain, placenta, lung, skeletal muscle, kidney, or pancreas. Using primer extension analysis, the transcription start site is located at nucleotide 98 upstream from the ATG initiating codon. Putative TATA and CAAT boxes are situated at positions 72 and 96 upstream from the transcription start site, respectively. Using DNA from a panel of human/rodent somatic cell hybrids, and amplification of the gene by the polymerase chain reaction, the human dehydroepiandrosterone sulfotransferase gene has been assigned to chromosome 19.

Inhibitory effects of medroxyprogesterone acetate (MPA) and the pure antiestrogen EM-219 on estrone (E1)-stimulated growth of dimethylbenz(a)anthracene (DMBA)-induced mammary carcinoma in the rat

Estrogens are well known to play a predominant role in promoting the growth of DMBA-induced mammary tumors in the rat. Estrone (E1), a steroid having weak estrogenic activity, is one of most important estrogens in post-menopausal women, where it is converted into the potent estrogen estradiol (E2) by 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) in many peripheral tissues, including the mammary gland. In this report, we have studied the effect of a new antiestrogen (EM-219) (N-butyl, N-methyl-11-(3', 17'beta-dihydroxy-17'alpha-ethinyl-estra-1'3'5'(10'), 14'-tetraen-7'alpha-yl) undecanamide) on E1-stimulated growth of DMBA-induced mammary tumors and compared its effect with that of medroxyprogesterone acetate (MPA) alone or in combination. After 18 days, ovariectomy (OVX) reduced total tumor area to 29.6 +/- 7.1% of the original size, while E1 (1.0 microgram, twice daily) caused a 139 +/- 21% increase in tumor size in OVX animals. MPA (1.5 mg, twice daily) partially reversed the stimulatory effect of E1 to 66.0 +/- 9.0%, while the antiestrogen EM-219 (40 micrograms, twice daily) decreased tumor size to 70.0 +/- 10%. Combination of these two compounds led to a further inhibition of tumor size to 30.7 +/- 7.4% of the value found in OVX animals treated with E1. Tumor E2 levels decreased from 1688 +/- 155 pmoles/kg tissue in OVX animals receiving E1 to 709 +/- 92, 1347 +/- 98, and 184 +/- 11 pmoles/kg tissue in MPA-, EM-219-, and MPA+EM-219-treated OVX-E1 animals, respectively. Treatment of OVX animals with E1 increased by 69% the reductive activity of 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) while MPA abolished completely this effect of E1. In the oxidative direction, treatment with E1, E1 + MPA, or E1 + EM-219 had minimal or no significant effect on the activity of 17 beta-HSD (vs OVX), while the combined treatment with MPA+EM-219 induced a 2-fold increase in 17 beta-HSD activity, thus leading to an increased conversion of E2 into E1. The present data show that combination of the pure antiestrogen EM-219 with MPA exerts a greater reduction in DMBA-induced mammary tumor growth and intratumoral E2 levels stimulated by E1 than either compound used alone. This interactive effect of the antiestrogen and MPA could at least partially be related to the increased inactivation of E2 into E1.(ABSTRACT TRUNCATED AT 400 WORDS)

Steroid gradients across the cancerous breast: an index of altered steroid metabolism in breast cancer?

The concentrations of 17 beta-estradiol, estrone, testosterone (T), dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulphate, androstenedione (A), cortisol and prolactin (PRL) were determined in the peripheral venous blood and in the lateral thoracic vein of 14 premenopausal and 34 postmenopausal women who underwent surgery for a breast carcinoma. The difference between the two blood samples, defined as concentration gradient across the cancerous breast, was calculated for all hormones. A significant peripheral-local concentration gradient was found for DHEA and A both in pre- and postmenopausal patients, whereas for T it was observed only in postmenopausal subjects. Furthermore, DHEA and A gradients were correlated to the presence of estrogen receptors as determined by a radioligand binding assay. An inverse relationship between DHEA gradient and the expression of estrogen receptors was observed in premenopausal women, whereas in postmenopausal patients an opposite, although not significant, trend was found. These results suggest that in the cancerous breast: (1) DHEA, A and T (the latter only in postmenopause) could be taken up from plasma, and thus there could be a storage of these steroids inside the breast tissue and/or perhaps some alterations in their local metabolism; (2) androgens could play a different role in breast carcinogenesis in relation to the estrogen circulating levels and to the expression of estrogen receptors.

Widespread tissue distribution of steroid sulfatase, 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD), 17 beta-HSD 5 alpha-reductase and aromatase activities in the rhesus monkey

Dehydroepiandrosterone-sulfate (DHEA-S), the main secretory product of the human adrenal, requires the presence of steroid sulfatase, 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD), 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD), 5 alpha-reductase, and aromatase to form the active androgen dihydrotestosterone (DHT) and the estrogens 17 beta-estradiol (E2) and 5-androst-ene-3 beta,17 beta-diol (delta 5-diol) in peripheral target tissues. Because humans, along with non-human primates are unique in having adrenals that secrete large amounts of DHEA-S, the present study investigated the tissue distribution of the enzymatic activity of the above-mentioned steroidogenic enzymes required for the formation of active sex steroids in the male and female rhesus monkey. Estrone and DHEA sulfatase activities were measured in all 25 tissues examined, and with the exception of the salivary glands, estrogenic and androgenic 17 beta-HSDs were present in all the tissues examined. The adrenal, small and large intestine, kidney, liver, lung, fat, testis, prostate, seminal vesicle, ovary, myometrium, and endometrium all possess the above-mentioned enzymatic activities, thus suggesting that these tissues could possibly form the biologically active steroids E2 and DHT from the adrenal precursor DHEA-S. On the other hand, the oviduct, cervix, mammary gland, heart, and skeletal muscle possess all the enzymatic activities required to synthesize E2 from DHEA-S. The present study describes the widespread tissue distribution of steroid sulfatase, 3 beta-HSD, 17 beta-HSD, 5 alpha-reductase, and aromatase activities in rhesus monkey peripheral tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunolocalization of aromatase and other steroidogenic enzymes in human breast disorders

Numerous studies have shown that human breast cancer tissue has the potential to synthesize estrogen through aromatization, which may act as a local growth factor of hormone-dependent cancer cells. This study was performed to localize the site of aromatization in human breast disorders by immunohistochemistry and correlate the findings with steroid receptors, clinicopathological findings, and other steroidogenic enzymes. Specimens from 60 cases of breast disorders, including 33 cases of breast cancer and 27 cases of benign proliferative disorders, were studied immunohistochemically for aromatase. In the carcinoma cases estrogen receptor (ER) and progesterone receptor (PgR) status was determined by enzyme immunoassay and immunohistochemistry, and other steroidogenic enzymes, including P450scc (side-chain cleavage), 3 beta HSD (hydroxysteroid dehydrogenase), and P450c17, were immunolocalized. Aromatase was immunolocalized in interstitial cells and adipocytes as well as other cells in both benign and malignant breast tissues. However, strong immunoreactivity was observed in adipocytes adjacent to carcinoma in all carcinoma cases and in interstitial or stromal cells around carcinomatous glands in 20 carcinoma cases. Intratumoral staining for aromatase did not correlate significantly with age, clinical stage, histopathological type, lymph nodes metastasis, or ER and PgR status. P450scc and 3 beta HSD were focally observed in 18 and 12 cases of carcinoma, respectively, but P450c17 was never observed. Aromatase expression in stromal or interstitial cells, including adipocytes, in breast cancer may be induced by carcinoma cells and locally synthesized estrogens could function as paracrine hormones. Intratumoral aromatase in human breast neoplasms correlated with malignant phenotypes but not with ER status or prognostic parameters, suggesting that other synthetic systems probably generate any biologically significant locally synthesized estrogens in hormone-dependent breast malignancy.

Metabolism of the oral contraceptive steroids ethynylestradiol, norgestimate and 3-ketodesogestrel by a human endometrial cancer cell line (HEC-1A) and endometrial tissue in vitro

Human endometrial cancer cells and human endometrial tissue have been extensively used to study steroid hormone action and metabolism. The natural estrogens estradial (E2) and estrone (E1) are known to be metabolized by both cells and tissue with the interconversion of the two steroids and the formation of sulphate conjugates. The aim of the present work was to see if the commonly used oral contraceptive steroids ethynylestradiol (EE2), norgestimate (Ngmate) and 3-ketodesogestrel (3-KDG) were metabolized by a human endometrial cancer cell line (HEC-1A) and human endometrial tissue in vitro. Metabolites were analysed by on-line radiometric HPLC. Endometrial tissue was obtained from women undergoing dilation and curettage or hysterectomy operations. In preliminary studies with endogenous estrogens, HEC-1A cells were able to interconvert E1 and E2; the equilibrium favouring the formation of E2. Normal endometrial tissue extensively converted E2 to E1, tumour tissue appeared to catalyse this reaction much less avidly. In addition sulphate conjugates were formed by normal tissue from some patients. Cell line and endometrial tissue was able to hydrolyse estrone 3-sulphate. With EE2 as substrate there was no evidence of phase I metabolism by cell line or tissue. However, conversion to the presumed 3-sulphate conjugate was observed following incubation with normal tissue from some women. Deacetylation of the progestogen Ngmate to norgestrel oxime (NgOx) was complete within 24 h. There was also some loss of the oxime moiety to give norgestrel (Ng) following incubation with HEC-1A cells. Metabolism of Ngmate was also complete within 24 h following incubation with endometrial tissue. There were both qualitative and quantitative differences in metabolite formation between tissue obtained from different women. In contrast, 3-KDG was relatively resistant to metabolism by cell line and tissue. The major metabolite formed by HEC-1A cells accounted for only 3.3 +/- 0.4% of total added radiolabelled steroid and co-chromatographed with 3 alpha-hydroxydesogestrel. Smaller amounts of other radiometabolites were formed. No phase I metabolites of 3-KDG were formed by normal endometrial tissue, however small amounts of radiometabolites appeared to be formed by malignant tissue. These studies have provided evidence to suggest that the oral contraceptives EE2, Ngmate and 3-KDG are metabolized in the human endometrium. Knowledge of the metabolism of these in target tissues such as the endometrium may be pertinent considering the possibility that metabolites may exert specific effects.

Structure, function and tissue-specific gene expression of 3β-hydroxysteroid dehydrogenase/5-ene-4-ene isomerase enzymes in classical and peripheral intracrine steroidogenic tissues

The membrane-bound enzyme 3β-hydroxysteroid dehydrogenase/5-ene-4-ene isomerase (3β-HSD) catalyses an essential step in the transformation of all 5-pregnen-3β-ol and 5-androsten-3β-ol steroids into the corresponding 3-keto-4-ene-steroids, namely progesterone as well as all the precursors of androgens, estrogens, glucocorticoids and mineralocorticoids. We have recently characterized two types of human 3β-HSD cDNA clones and the corresponding genes which encode type I and II 3β-HSD isoenzymes of 372 and 371 amino acids, respectively, and share 93.5% homology. The human 3β-HSD genes containing 4 exons were assigned by in situ hybridization to the p11-p13 region of the short arm of chromosome 1. Human type I 3β-HSD is the almost exclusive mRNA species present in the placenta and skin while the human type II is the predominant mRNA species in the adrenals, ovaries and testes. The type I protein possesses higher 3β-HSD activity than type II. We elucidated the structures of three types of rat 3β-HSD cDNAs as well that of one type of 3β-HSD from bovine and macaque ovary λgt11 cDNA libraries, which all encode a 372 amino acid protein. The rat type I and II 3β-HSD proteins expressed in the adrenals, gonads and adipose tissue share 93.8% homology. Transient expression of human type I and II as well as rat type I and II 3β-HSD cDNAs in HeLa human cervical carcinoma cells reveals that 3β-ol dehydrogenase and 5-ene-4-ene isomerase activities reside within a single protein. These expressed 3β-HSD proteins convert 3β-hydroxy-5-ene-steroids into 3-keto-4-ene derivatives and catalyze the interconversion of 3β-hydroxy and 3-keto-5α-androstane steroids. By site-directed mutagenesis, we demonstrated that the lower activity of expressed rat type II compared to rat type I 3β-HSD is due to a change of four residues probably involved in a membrane-spanning domain. When homogenates from cells transfected with a plasmid vector containing rat type I 3β-HSD is incubated in the presence of dihydrotestosterone (DHT) using NAD⁺ as co-factor, 5α-androstanedione was formed (A-dione), indicating an intrinsic androgenic 17β-hydroxysteroid dehydrogenase (17β-HSD) activity of this 3β-HSD. We cloned a third type of rat cDNA encoding a predicted type III 3β-HSD specifically expressed in the rat liver, which shares 80% similarity with the two other isoenzymes. Transient expression in human HeLa cells reveals that the type III isoenzyme does not display oxidative activity for the classical substrates of 3β-HSD. However, in common with the type I enzyme, it converts A-dione and DHT to the corresponding 3β-hydroxysteroids, thus showing an exclusive 3-ketosteroid reductase activity. When NADPH is used as co-factor, the affinity for DHT of the type III enzyme becomes 10-fold higher than that of the type I. Rat type III mRNA was below the detection limit in intact female liver. Following hypophysectomy, its concentration increased to 55% of the values measured in intact or hypophysectomized male rats, an increase which can be blocked by administration of ovine prolactin (oPRL). Treatment with oPRL for 10 days starting 15 days after hypophysectomy markedly decreased ovarian 3β-HSD mRNA accumulation accompanied by a similar decrease in 3β-HSD activity and protein levels. Treatment with the gonadotropin hCG reversed the potent inhibitory effect of oPRL on these parameters and stimulated 3β-HSD mRNA levels in ovarian interstitial cells. These data indicate that the presence of multiple 3β-HSD isoenzymes offers the possibility of tissue-specific expression and regulation of this enzymatic activity that plays an essential role in the biosynthesis of all hormonal steroids in classical as well as peripheral intracrine steroidogenic tissues.

Distribution of 17 beta-hydroxysteroid dehydrogenase gene expression and activity in rat and human tissues

The interconversion of estrone (E1) and 17 beta-estradiol (E2), androstenedione (4-ene-dione) and testosterone (T), as well as dehydroepiandrosterone and androst-5-ene-3 beta,17 beta-diol is catalyzed by 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD). The enzyme 17 beta-HSD thus plays an essential role in the formation of all active androgens and estrogens in gonadal as well as extragonadal tissues. The present study investigates the tissue distribution of 17 beta-HSD activity in the male and female rat as well as in some human tissues and the distribution of 17 beta-HSD mRNA in some human tissues. Enzymatic activity was measured using 14C-labeled E1, E2, 4-ene-dione and T as substrates. Such enzymatic activity was demonstrated in all 17 rat tissues examined for both androgenic and estrogenic substrates. While the liver had the highest level of 17 beta-HSD activity, low but significant levels of E2 as well as T formation were found in rat brain, heart, pancreas and thymus. The oxidative pathway (E2----E1, T----4-ene-dione) was favored over the reverse reaction in almost all rat tissues while in the human, almost equal rates were found in most of the 15 tissues examined. The widespread distribution of 17 beta-HSD in rat and human tissues clearly indicates the importance of this enzyme in peripheral sex steroid formation or intracrinology.