Overexpression of Human Estrogen Biosynthetic Enzyme Hydroxysteroid (17beta) Dehydrogenase Type 1 Induces Adenomyosis-like Phenotype in Transgenic Mice.

Hydroxysteroid (17beta) dehydrogenase type 1 (HSD17B1) is an enzyme that converts estrone to estradiol, while adenomyosis is an estrogen-dependent disease with poorly understood pathophysiology. In the present study, we show that mice universally over-expressing human estrogen biosynthetic enzyme HSD17B1 (HSD17B1TG mice) present with adenomyosis phenotype, characterized by histological and molecular evaluation. The first adenomyotic changes with endometrial glands partially or fully infiltrated into the myometrium appeared at the age of 5.5 months in HSD17B1TG females and became more prominent with increasing age. Preceding the phenotype, increased myometrial smooth muscle actin positivity and increased amount of glandular myofibroblast cells were observed in HSD17B1TG uteri. This was accompanied by transcriptomic upregulation of inflammatory and estrogen signaling pathways. Further, the genes upregulated in the HSD17B1TG uterus were enriched with genes previously observed to be induced in the human adenomyotic uterus, including several genes of the NFKB pathway. A 6-week-long HSD17B1 inhibitor treatment reduced the occurrence of the adenomyotic changes by 5-fold, whereas no effect was observed in the vehicle-treated HSD17B1TG mice, suggesting that estrogen is the main upstream regulator of adenomyosis-induced uterine signaling pathways. HSD17B1 is considered as a promising drug target to inhibit estrogen-dependent growth of endometrial disorders. The present data indicate that HSD17B1 over-expression in TG mice results in adenomyotic changes reversed by HSD17B1 inhibitor treatment and HSD17B1 is, thus, a potential novel drug target for adenomyosis.

Pharmacological inhibition of 17ß-hydroxysteroid dehydrogenase impairs human endometrial cancer growth in an orthotopic xenograft mouse model.

Endometrial cancer (EC) is the most common gynaecological tumor in developed countries and its incidence is increasing. Approximately 80% of newly diagnosed EC cases are estrogen-dependent. Type 1 17ß-hydroxysteroid dehydrogenase (17ß-HSD-1) is the enzyme that catalyzes the final step in estrogen biosynthesis by reducing the weak estrogen estrone (E1) to the potent estrogen 17ß-estradiol (E2), and previous studies showed that this enzyme is implicated in the intratumoral E2 generation in EC. In the present study we employed a recently developed orthotopic and estrogen-dependent xenograft mouse model of EC to show that pharmacological inhibition of the 17ß-HSD-1 enzyme inhibits disease development. Tumors were induced in one uterine horn of athymic nude mice by intrauterine injection of the well-differentiated human endometrial adenocarcinoma Ishikawa cell line, modified to express human 17ß-HSD-1 in levels comparable to EC, and the luciferase and green fluorescent protein reporter genes. Controlled estrogen exposure in ovariectomized mice was achieved using subcutaneous MedRod implants that released either the low active estrone (E1) precursor or vehicle. A subgroup of E1 supplemented mice received daily oral gavage of FP4643, a well-characterized 17ß-HSD-1 inhibitor. Bioluminescence imaging (BLI) was used to measure tumor growth non-invasively. At sacrifice, mice receiving E1 and treated with the FP4643 inhibitor showed a significant reduction in tumor growth by approximately 65% compared to mice receiving E1. Tumors exhibited metastatic spread to the peritoneum, to the lymphovascular space (LVI), and to the thoracic cavity. Metastatic spread and LVI invasion were both significantly reduced in the inhibitor-treated group. Transcriptional profiling of tumors indicated that FP4643 treatment reduced the oncogenic potential at the mRNA level. In conclusion, we show that 17ß-HSD-1 inhibition represents a promising novel endocrine treatment for EC.

Intracrine Regulation of Estrogen and Other Sex Steroid Levels in Endometrium and Non-gynecological Tissues; Pathology, Physiology, and Drug Discovery.

Our understanding of the intracrine (or local) regulation of estrogen and other steroid synthesis and degradation expanded in the last decades, also thanks to recent technological advances in chromatography mass-spectrometry. Estrogen responsive tissues and organs are not passive receivers of the pool of steroids present in the blood but they can actively modify the intra-tissue steroid concentrations. This allows fine-tuning the exposure of responsive tissues and organs to estrogens and other steroids in order to best respond to the physiological needs of each specific organ. Deviations in such intracrine control can lead to unbalanced steroid hormone exposure and disturbances. Through a systematic bibliographic search on the expression of the intracrine enzymes in various tissues, this review gives an up-to-date view of the intracrine estrogen metabolisms, and to a lesser extent that of progestogens and androgens, in the lower female genital tract, including the physiological control of endometrial functions, receptivity, menopausal status and related pathological conditions. An overview of the intracrine regulation in extra gynecological tissues such as the lungs, gastrointestinal tract, brain, colon and bone is given. Current therapeutic approaches aimed at interfering with these metabolisms and future perspectives are discussed.

Development of an Image-Guided Orthotopic Xenograft Mouse Model of Endometrial Cancer with Controllable Estrogen Exposure.

Endometrial cancer (EC) is the most common gynaecological malignancy in Western society and the majority of cases are estrogen dependent. While endocrine drugs proved to be of insufficient therapeutic value in the past, recent clinical research shows promising results by using combinational regimens and pre-clinical studies and identified potential novel endocrine targets. Relevant pre-clinical models can accelerate research in this area. In the present study we describe an orthotopic and estrogen dependent xenograft mouse model of EC. Tumours were induced in one uterine horn of female athymic nude mice using the well-differentiated human endometrial adenocarcinoma Ishikawa cell line-modified to express the luciferase gene for bioluminescence imaging (BLI). BLI and contrast-enhanced computed-tomograph (CE-CT) were used to measure non-invasive tumour growth. Controlled estrogen exposure was achieved by the use of MedRod implants releasing 1.5 µg/d of 17ß-estradiol (E2) in ovariectomized mice. Stable E2 serum concentration was demonstrated by LC-MS/MS. Induced tumours were E2 responsive as increased tumour growth was observed in the presence of E2 but not placebo, assessed by BLI, CE-CT, and tumour weight at sacrifice. Metastatic spread was assessed macroscopically by BLI and histology and was seen in the peritoneal cavity, in the lymphovascular space, and in the thoracic cavity. In conclusion, we developed an orthotopic xenograft mouse model of EC that exhibits the most relevant features of human disease, regarding metastatic spread and estrogen dependency. This model offers an easy to manipulate estrogen dosage (by simply adjusting the MedRod implant length), image-guided monitoring of tumour growth, and objectively measurable endpoints (including tumour weight). This is an excellent in vivo tool to further explore endocrine drug regimens and novel endocrine drug targets for EC.

Blocking oestradiol synthesis pathways with potent and selective coumarin derivatives.

A comprehensive set of 3-phenylcoumarin analogues with polar substituents was synthesised for blocking oestradiol synthesis by 17-ß-hydroxysteroid dehydrogenase 1 (HSD1) in the latter part of the sulphatase pathway. Five analogues produced ≥62% HSD1 inhibition at 5 µM and, furthermore, three of them produced ≥68% inhibition at 1 µM. A docking-based structure-activity relationship analysis was done to determine the molecular basis of the inhibition and the cross-reactivity of the analogues was tested against oestrogen receptor, aromatase, cytochrome P450 1A2, and monoamine oxidases. Most of the analogues are only modestly active with 17-ß-hydroxysteroid dehydrogenase 2 - a requirement for lowering effective oestradiol levels in vivo. Moreover, the analysis led to the synthesis and discovery of 3-imidazolecoumarin as a potent aromatase inhibitor. In short, coumarin core can be tailored with specific ring and polar moiety substitutions to block either the sulphatase pathway or the aromatase pathway for treating breast cancer and endometriosis.

Structure-Activity Relationship Analysis of 3-Phenylcoumarin-Based Monoamine Oxidase B Inhibitors.

Monoamine oxidase B (MAO-B) catalyzes deamination of monoamines such as neurotransmitters dopamine and norepinephrine. Accordingly, small-molecule MAO-B inhibitors potentially alleviate the symptoms of dopamine-linked neuropathologies such as depression or Parkinson's disease. Coumarin with a functionalized 3-phenyl ring system is a promising scaffold for building potent MAO-B inhibitors. Here, a vast set of 3-phenylcoumarin derivatives was designed using virtual combinatorial chemistry or rationally de novo and synthesized using microwave chemistry. The derivatives inhibited the MAO-B at 100 nM-1 µM. The IC50 value of the most potent derivative 1 was 56 nM. A docking-based structure-activity relationship analysis summarizes the atom-level determinants of the MAO-B inhibition by the derivatives. Finally, the cross-reactivity of the derivatives was tested against monoamine oxidase A and a specific subset of enzymes linked to estradiol metabolism, known to have coumarin-based inhibitors. Overall, the results indicate that the 3-phenylcoumarins, especially derivative 1, present unique pharmacological features worth considering in future drug development.

Blocking 17ß-hydroxysteroid dehydrogenase type 1 in endometrial cancer: a potential novel endocrine therapeutic approach.

The enzyme type 1 17ß-hydroxysteroid dehydrogenase (17ß-HSD-1), responsible for generating active 17ß-estradiol (E2) from low-active estrone (E1), is overexpressed in endometrial cancer (EC), thus implicating an increased intra-tissue generation of E2 in this estrogen-dependent condition. In this study, we explored the possibility of inhibiting 17ß-HSD-1 and impairing the generation of E2 from E1 in EC using in vitro, in vivo, and ex vivo models. We generated EC cell lines derived from the well-differentiated endometrial adenocarcinoma Ishikawa cell line and expressing levels of 17ß-HSD-1 similar to human tissues. In these cells, HPLC analysis showed that 17ß-HSD-1 activity could be blocked by a specific 17ß-HSD-1 inhibitor. In vitro, E1 administration elicited colony formation similar to E2, and this was impaired by 17ß-HSD-1 inhibition. In vivo, tumors grafted on the chicken chorioallantoic membrane (CAM) demonstrated that E1 upregulated the expression of the estrogen responsive cyclin A similar to E2, which was impaired by 17ß-HSD-1 inhibition. Neither in vitro nor in vivo effects of E1 were observed using 17ß-HSD-1-negative cells (negative control). Using a patient cohort of 52 primary ECs, we demonstrated the presence of 17ß-HSD-1 enzyme activity (ex vivo in tumor tissues, as measured by HPLC), which was inhibited by over 90% in more than 45% of ECs using the 17ß-HSD-1 inhibitor. Since drug treatment is generally indicated for metastatic/recurrent and not primary tumor, we next demonstrated the mRNA expression of the potential drug target, 17ß-HSD-1, in metastatic lesions using a second cohort of 37 EC patients. In conclusion, 17ß-HSD-1 inhibition efficiently blocks the generation of E2 from E1 using various EC models. Further preclinical investigations and 17ß-HSD-1 inhibitor development to make candidate compounds suitable for the first human studies are awaited. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Metabolism and metabolite profiles in vitro and in vivo of ospemifene in humans and preclinical species.

BACKGROUND: Metabolite profiles of ospemifene, a novel nonsteroidal selective estrogen receptor modulator, were surveyed as part of its development. METHODS: The pharmacokinetics of ospemifene and its two major, pharmacologically active metabolites 4-hydroxyospemifene and 4'-hydroxyospemifene, was elucidated in studies of volunteer humans given various doses of ospemifene and in experiments of several animal species (rat, mouse, dog, and cynomolgus monkey), which had been used either for pharmacological or toxicological studies of ospemifene. Metabolites produced in in vitro human and animal liver preparations were compared between species and with the metabolite profiles in the in vivo investigations. RESULTS: Considerable interspecies differences were observed in the metabolite profiles and quantities. The major human metabolite, 4-hydroxyospemifene, was produced in substantial amounts both in vitro and in vivo in most animal species, except dog, and thus the exposure to this metabolite seems adequate in the most important toxicology species, the rat and the cynomolgus monkey. 4'-Hydroxyospemifene was equally abundant in vitro and in vivo metabolite in mice and dogs, and consequently, its contribution to the total exposure of ospemifene-related activity would be adequately covered in animal experiments. Other ospemifene metabolites were variably detected in different species, but probably they are not of consequence to pharmacology or toxicology of ospemifene. CONCLUSIONS: Overall, there are quantitative and also some qualitative differences in the metabolism of ospemifene in different species. Generally, in vitro metabolite profiles were predictive for in vivo profiles. The contribution of two major hydroxyl metabolites to activity and toxicity of ospemifene is adequately covered by at least some animal species.

HSD17B1 expression enhances estrogen signaling stimulated by the low active estrone, evidenced by an estrogen responsive element-driven reporter gene in vivo.

Hydroxysteroid (17beta) dehydrogenase 1 (HSD17B1) belongs to a family of short-chain-dehydrogenases. The enzyme utilizes NAD(P) and NAD(P)H as cofactors, and catalyzes the reversible reaction between estrone (E1) and estradiol (E2) in vitro. Of these steroids, E1 presents with lower estrogenic activity, but is converted to highly active E2 by HSD17B1. HSD17B1 is expressed especially in tissues with a high E2-producing capacity such as human ovaries and placenta, but also in several peripheral estrogen target tissues in humans, and inhibiting the enzyme activity is, thus, considered a promising approach to treat estrogen-dependent diseases. By analyzing transgenic mice universally expressing human HSD17B1 and carrying estrogen-response element (ERE)-driven luciferase reporter gene (Bi-transgenic ERELuc-HSD17B1TG mice) we showed a markedly higher reporter gene activity in various peripheral tissues of these mice as compared with ERELuc mice, indicating enhanced estrogen response generated by human HSD17B1 expression. An increased response after E1 administration was also evident in the Bi-TG mice, indicated by the increased uterus growth response and by the higher ERELuc reporter gene activity in the uterus. Moreover, a HSD17B1 inhibitor significantly reduced E1-induced increase in the uterus weight and uterine epithelial proliferation in the Bi-TG mice. Also the E1-induced ERELuc activity in the inhibitor-treated uterus was reduced by the HSD17B1 inhibitor in immature mice ex vivo, as well as in the liver of adult mice. The data, thus, demonstrate the potential use of the Bi-TG mice as a preclinical in vivo model for screening the efficacy of HSD17B1 inhibitors. As compared with the existing models, the Bi-TG mice present with luciferase activity as an additional, easily quantitative endpoint for the estrogen action.

Inhibition of type 1 17ß-hydroxysteroid dehydrogenase impairs the synthesis of 17ß-estradiol in endometriosis lesions.

CONTEXT: Endometriosis affects 10% of the women before menopause and has important personal, professional, and societal economic burdens. Because current medical treatments are aimed at reducing the symptoms only, novel therapeutic targets should be identified. Endometriosis is estrogen dependent and in some patients the endometriosis tissue is able to produce estrogens in an autocrine/paracrine manner. In a number of patients, this is the consequence of the high local activity of the 17ß-hydroxysteroid-dehydrogenases (17ß-HSDs), enzymes able to generate active estrogens from precursors with low activity. OBJECTIVE: The objective of the study was to identify the 17ß-HSD(s) responsible for the high local generation of estrogens in endometriosis and test the possibility to inhibit these enzymes for therapeutic purposes. DESIGN: The expression of different 17ß-HSDs involved in the estrogen metabolism was assessed by real-time PCR in eutopic and ectopic tissue from endometriosis patients (n=14). These biopsies had previously confirmed unbalanced local 17ß-HSD activity, which caused high estrogen generation. The possibility to block the synthesis of estrogens by one inhibitor specific for type 1 17ß-HSD was assessed by HPLC in tissue lysates from endometriosis tissues (n=27). RESULTS: In all but one of the patients, a high type 1 17ß-HSD level is associated with the unbalanced metabolism of estrogens, leading to higher estrogen synthesis in endometriosis than in the endometrium inside the uterus. Inhibition of type 1 17ß-HSD restores to various extents, depending on the patient, the correct metabolism. In 19 of 27 patients analyzed (70%), the 17ß-HSD type 1 inhibitor decreased the generation of 17ß-estradiol by greater than 85%. CONCLUSIONS: Inhibition of 17ß-HSD type 1 can be a potential future treatment option aimed at restoring the correct metabolic balance of estrogens in endometriosis patients with increased local 17ß-HSD type 1 enzyme activity.

Single-dose and steady-state pharmacokinetics of ospemifene, a selective estrogen receptor modulator, in postmenopausal women.

OBJECTIVE: To characterize the pharmacokinetics of the oral, non-estrogen agent ospemifene, an estrogen agonist/antagonist with tissue-selective effects (also called a selective estrogen receptor modulator) that was recently approved for the treatment of dyspareunia associated with vulvar and vaginal atrophy in postmenopausal women. METHODS: Two open-label, Phase 1 studies were conducted to determine the pharmacokinetics of ospemifene in healthy postmenopausal women. In the single-dose study, 60 mg of [3H]-ospemifene was orally administered to 6 subjects. Blood, urine, and fecal samples were collected predose and serially up to 240 hours postdose. In the multiple-dose study, 12 subjects received 60 mg of ospemifene once daily for 9 days. Blood samples were collected predose and serially postdose on Day 1, predose on Days 7 and 8, and predose and serially postdose on Day 9. RESULTS: Ospemifene exhibited high plasma protein binding and was extensively metabolized, predominantly to 4-hydroxyospemifene and 4'-hydroxyospemifene. In the single-dose study, ospemifene was rapidly absorbed, with a median tmax of 1.50 hours and geometric mean Cmax of 612 ng/ml. The geometric mean (CV%) t1/2 was 24.5 (21.3) hours and 29.0 (18.0) hours for ospemifene and 4-hydroxyospemifene, respectively. Fecal elimination accounted for 75% of the administered [3H]-ospemifene dose in 240 hours. In the multiple dosing study, steady state was reached by Day 7. The mean t1/2 at steady state for ospemifene was 29.1 hours. High values for volume of distribution and total clearance suggested extensive tissue distribution and efficient elimination of ospemifene. CONCLUSIONS: In healthy postmenopausal women, ospemifene 60 mg/day reached steady state concentrations by Day 7 and showed minimal accumulation of parent drug or its two main metabolites, indicating that once daily dosing is appropriate.

Oral bioavailability of ospemifene improves with food intake.

OBJECTIVE: To assess the effect of concomitant food intake on the relative bioavailability of ospemifene and its main metabolite, 4-hydroxyospemifene, after single oral dosing. METHODS: This was an open-label, randomized, balanced, two-treatment (fed vs. fasted), two-period, two-sequence cross-over study in 24 healthy male subjects. Single 60-mg doses of ospemifene were administered without food or with a high-fat, high-energy breakfast (860 kcal). In an extension study, a single 60-mg dose of ospemifene was given to 12 subjects with a low-fat, light breakfast (300 kcal). Additional information was acquired by determining tablet dissolution profiles in media which reflected fasted and fed intestinal conditions. RESULTS: The AUC0-72 h and Cmax of ospemifene were 2.8- and 3.6-fold higher after a high-fat breakfast and 1.9- and 2.3-fold higher after a low-fat breakfast when compared with an overnight fast. The variability in both primary pharmacokinetic parameters was considerably reduced (by up to 50%) with a meal, indicating more consistent absorption of ospemifene with concomitant food intake. Dissolution in conditions simulating fed intestinal fluid (high bile acid concentration) was increased 3-fold compared with dissolution in simulated fasted intestinal fluid. CONCLUSIONS: wood markedly enhanced the extent and predictability of ospemifene absorption. The increase in bioavailability was not linearly related with the fat content of the meal. In vitro dissolution results were consistent with these clinical observations. Administration with food enhances and standardizes the oral bioavailability of ospemifene. Thus, it is recommended that ospemifene tablets should be taken with food.

Ospemifene metabolism in humans in vitro and in vivo: metabolite identification, quantitation, and CYP assignment of major hydroxylations.

BACKGROUND: The metabolism of ospemifene, a novel nonsteroidal selective estrogen receptor modulator, was investigated as part of its development. METHODS: Metabolite identification, tentative quantitation, and CYP assignment of ospemifene were performed in human liver microsomes or homogenate incubations and in plasma samples from volunteer humans. The potential contributions of CYP enzymes were determined by recombinant human CYPs. Metabolite identification and tentative quantification were performed by liquid chromatography-mass spectrometry. RESULTS: The relative abundances of metabolites produced were dependent on ospemifene concentration and liver preparation, but the largest quantities of 4- and 4'-hydroxy-ospemifene (and their glucuronides in smaller quantities) were produced in human liver microsomes at low ospemifene concentrations. Other metabolites were detected in in vitro incubation with human liver including a direct glucuronide of ospemifene and some metabolites with only minor abundance. In human plasma samples, 4-hydroxy-ospemifene was the most abundant metabolite, representing about 25% of the abundance of the parent compound. All the other metabolites detected in plasma, including 4'-hydroxy-ospemifene, represented <7% of the abundance of ospemifene. Several CYP enzymes participated in 4-hydroxylation, including CYP2C9, CYP2C19, CYP2B6, and CYP3A4, whereas CYP3A enzymes were the only ones to catalyze 4'-hydroxylation. CONCLUSIONS: In vitro incubations with liver preparations provided a rather reliable starting point in the search for potential metabolites in clinical settings. The in vitro metabolite profile is informative for the in vivo metabolite profile, especially regarding the major hydroxylated metabolites. However, it is anticipated that extended in vivo exposures may result in an increased production of more distal metabolites from major metabolites.

Novel hydroxysteroid (17beta) dehydrogenase 1 inhibitors reverse estrogen-induced endometrial hyperplasia in transgenic mice.

Local estrogen production plays a key role in proliferative endometrial disorders, such as endometrial hyperplasia and cancer. Hydroxysteroid (17beta) dehydrogenase 1 (HSD17B1) is an enzyme that catalyzes with high efficiency the conversion of weakly active estrone into highly potent estradiol. Here we report that female transgenic mice expressing human HSD17B1 invariably develop endometrial hyperplasia in adulthood. These mice also fail to ovulate and have enhanced peripheral conversion of estrone into estradiol in a variety of target tissues, including the uterus. As in humans, endometrial hyperplasia in HSD17B1 transgenic female mice was reversible on ovulation induction, which triggers a rise in circulating progesterone levels, and in response to exogenous progestins. Strikingly, a treatment with an HSD17B1 inhibitor failed to restore ovulation yet completely reversed the hyperplastic morphology of epithelial cells in the glandular compartment, although less so in the luminal epithelium. The data indicate that human HSD17B1 expression enhances endometrial estrogen production, and consequently, estrogen-dependent proliferation. Therefore, HSD17B1 is a promising new therapeutic target in the management of estrogen-dependent endometrial diseases.

Synthesis and biological evaluation of 17beta-hydroxysteroid dehydrogenase type 1 (17beta-HSD1) inhibitors based on a thieno[2,3-d]pyrimidin-4(3H)-one core.

Many breast tumors are hormone-dependent, and estrogens, especially estradiol (E2), have a pivotal role in their growth and development. 17beta-Hydroxysteroid dehydrogenase type 1 (17beta-HSD1) is a key enzyme in the biosynthesis of female sex steroids, catalyzing the NADPH-dependent reduction of estrone into biologically active estradiol. In this study, a library of fused (di)cycloalkeno thieno[2,3-d]pyrimidin-4(3H)-one based compounds was synthesized, and the biological activities against 17beta-HSD1 in a cell-free and in a cell-based assay were evaluated. Several thieno[2,3-d]pyrimidin-4(3H)-one based compounds, at 0.1 and 1 muM test concentrations, were found to be potent 17beta-HSD1 inhibitors. For example, 4-(3-hydroxyphenylthio)-1,2,7,8,9,10,11,13-octahydro-13-oxo-[1]benzothieno[2',3':4,5]-pyrimido[1,2-a]azepine-3-carboxaldehyde (7f) is one of the most potent nonsteroidal 17beta-HSD1 inhibitors reported to date with 94% inhibition of the recombinant enzyme at 0.1 muM test concentration. Importantly, the majority of these compounds exhibited excellent selectivity over the oxidative isoform 17beta-HSD2 and lacked estrogenic effects in an estrogen receptor (ER) binding assay.

In vivo mouse model for analysis of hydroxysteroid (17beta) dehydrogenase 1 inhibitors.

Hydroxysteroid (17beta) dehydrogenase 1 (HSD17B1) catalyzes the reaction between the low active 17-ketosteroids and the highly active 17beta-hydroxysteroids. In the present study, we have generated transgenic (TG) mice expressing human (h) HSD17B1 under mouse mammary tumor virus (MMTV) promoter (MMTV-hHSD17B1TG mice). The MMTV-hHSD17B1TG mice were used to characterize HSD17B1 enzyme activity and properties of HSD17B1 inhibitor in vivo. Expression of the transgene was detected by enzyme activity and RT-PCR analysis. Increased HSD17B1 activity in the TG mice was detected in vivo by applying estrone as a substrate via an intravenous injection. The developed enzyme activity measurement was then applied to analyze the efficacy of HSD17B1 inhibitor in vivo. The results indicated that the MMTV-hHSD17B1TG mouse model is a valuable novel tool to test human HSD17B1 inhibition by various compounds in vivo. With the potent hHSD17B1 inhibitor compound tested, at highest an 85% and 33% inhibition of the enzyme activity in males and in females, respectively, was observed.

Estrone C15 derivatives--a new class of 17beta-hydroxysteroid dehydrogenase type 1 inhibitors.

Lowering local estradiol concentration by inhibition of the estradiol-synthesizing enzyme 17beta-hydroxysteroid dehydrogenase type 1 (17beta-HSD1) has been proposed as a promising new therapeutic option to treat estrogen-dependent diseases like endometriosis and breast cancer. Based on a molecular modelling approach we designed and synthesized novel C15-substituted estrone derivatives. Subsequent biological evaluation revealed that potent inhibitors of human 17beta-HSD1 can be identified in this compound class. The best, compound 21, inhibited recombinant human 17beta-HSD1 with an IC50 of 10nM and had no effect on the activity of recombinant human 17beta-hydroxysteroid dehydrogenase type 2 (17beta-HSD2), the enzyme catalyzing estradiol inactivation. These properties were retained in a cell-based enzyme activity assays. In spite of the estrogen backbone compound 21 did not show estrogen receptor mediated effects in vitro or in vivo. In conclusion, estrone C15 derivative compound 21 can be regarded as a promising lead compound for further development as a 17beta-HSD1 inhibitor.

New inhibitors of 17beta-hydroxysteroid dehydrogenase type 1.

The estradiol-synthesizing enzyme 17beta-hydroxysteroid dehydrogenase type 1 (17betaHSD1) is mainly responsible for the conversion of estrone (E1) to the potent estrogen estradiol (E2). It is a key player to control tissue levels of E2 and is therefore an attractive target in estradiol-dependent diseases like breast cancer or endometriosis. We selected a unique non-steroidal pyrimidinone core to start a lead optimization program. We optimized this core by modulation of R1-R6. Its binding mode at the substrate-binding site of 17betaHSD1 is complex and difficult to predict. Nevertheless, some basic structure-activity relationships could be identified. In vitro, the most active pyrimidinone derivative showed effective inhibition of recombinant human 17betaHSD1 at nanomolar concentrations. In intact cells overexpressing the human enzyme, IC50 values in the lower micromolar range were determined. Furthermore, the pyrimidinone proved its use in vivo by significantly reducing 17betaHSD1-dependent tumor growth in a new nude mouse model.

Screening of some anti-androgenic endocrine disruptors using a recombinant cell-based in vitro bioassay.

The present work describes the development and optimization of a cell-based androgen reporter assay using the Chinese hamster ovarian cell line (CHO K1) in the 96-well format. The recent reports on increasing exposure of humans and wild-life to environmental endocrine disrupting chemicals (ED) prompt the need for high throughput screening systems for such compounds in environmental and biological samples. To this end, CHO cells were cotransfected with plasmids encoding mouse mammary tumour virus-neomycin-luciferase and human androgen receptor (hAR), and a stable cell line was established. After selection with neomycin, a highly active clone was obtained which stably expressed both the hAR and the androgen-responsive luciferase reporter. Stimulation of the cells with androgens for 24 h resulted in about 15-fold stimulation of luciferase activity, with the minimum effective dose of testosterone being 0.1 nmol/l. Potent steroidal and non-steroidal anti-androgens, such as hydroxyflutamide and cyproterone acetate, significantly inhibited the androgen-induced transactivation. Non-androgenic steroids like estradiol, progesterone, dexamethasone and cortisol showed weak activity at high concentrations. RT-PCR and western blot confirmed proper transcription and translation as well as stable expression of the AR gene in the cells. About 60 different chemicals (mostly pesticides or their metabolites, and common industrial chemicals) were screened with the cell line for their ability to stimulate luciferase activity or inhibit that evoked by 0.1 nmol/l R1881, used as a positive androgenic control. About 10 highly potent anti-androgenic chemicals were identified. The most potent anti-androgenic compounds identified in our assay included bisphenol A, alpha-hexachlorocyclohexane, vinclozolin and 4,4-DDE. These compounds had alone either no effect or were weak agonists (with cytotoxic effects at very high concentrations), but none showed any significant agonistic activity. In conclusion, we demonstrate that the bioassay based on this cell line provides a reliable test for detecting androgenic and anti-androgenic compounds. The 96-well plate format makes the assay suitable for high throughput screening.

Female mice carrying a ubiquitin promoter-Insl3 transgene have descended ovaries and inguinal hernias but normal fertility.

Mouse knockout studies have indicated that Insl3 is involved in development of the gubernaculum in males, which is essential for normal testicular descent. To determine further the functions of Insl3 we have generated transgenic (TG) mice ubiquitously expressing Insl3. In these mice low levels of transgenic Insl3 mRNA are expressed in all tissues analyzed. In the TG females the ovaries descend to the base of the abdominal cavity during the fetal period, as a consequence of the formation of male-like gubernaculum structures. Furthermore, the gubernacular structures developed express androgen receptor, identically to the corresponding structures in males. At adult age the ligaments formed connect the uterine horns to the inguinal region of the abdomen. Ligaments are also formed between the lower and upper parts of the uterine horns, and these ligaments force the uterus to form a coiled structure. However, the TG females retain their reproductive functions, indicating that neither the location of the ovaries nor the macroscopic structure of the uterus is vital for reproduction. In addition, Insl3 expression causes inguinal hernia in females, suggesting that a combination of estrogen and Insl3 action disrupts proper development of the muscular and connective tissue structures of the abdomen. The lack of a phenotype in other tissues indicates that gubernaculum formation is the most sensitive biological response as regards Insl3.