Tissue-specific promoters regulate aromatase cytochrome P450 expression

Nuclear Estrogen Receptors in Prostate Cancer: From Genes to Function

Estrogens are almost ubiquitous steroid hormones that are essential for development, metabolism, and reproduction. They exert both genomic and non-genomic action through two nuclear receptors (ERα and ERβ), which are transcription factors with disregulated functions and/or expression in pathological processes. In the 1990s, the discovery of an additional membrane estrogen G-protein-coupled receptor augmented the complexity of this picture. Increasing evidence elucidating the specific molecular mechanisms of action and opposing effects of ERα and Erβ was reported in the context of prostate cancer treatment, where these issues are increasingly investigated. Although new approaches improved the efficacy of clinical therapies thanks to the development of new molecules targeting specifically estrogen receptors and used in combination with immunotherapy, more efforts are needed to overcome the main drawbacks, and resistance events will be a challenge in the coming years. This review summarizes the state-of-the-art on ERα and ERβ mechanisms of action in prostate cancer and promising future therapies.

Brain-derived estrogen and neural function

Although classically known as an endocrine signal produced by the ovary, 17β-estradiol (E₂) is also a neurosteroid produced in neurons and astrocytes in the brain of many different species. In this review, we provide a comprehensive overview of the localization, regulation, sex differences, and physiological/pathological roles of brain-derived E₂ (BDE₂). Much of what we know regarding the functional roles of BDE₂ has come from studies using specific inhibitors of the E₂ synthesis enzyme, aromatase, as well as the recent development of conditional forebrain neuron-specific and astrocyte-specific aromatase knockout mouse models. The evidence from these studies support a critical role for neuron-derived E₂ (NDE₂) in the regulation of synaptic plasticity, memory, socio-sexual behavior, sexual differentiation, reproduction, injury-induced reactive gliosis, and neuroprotection. Furthermore, we review evidence that astrocyte-derived E₂ (ADE₂) is induced following brain injury/ischemia, and plays a key role in reactive gliosis, neuroprotection, and cognitive preservation. Finally, we conclude by discussing the key controversies and challenges in this area, as well as potential future directions for the field.

Aromatase Inhibitors for the Treatment of Breast Cancer: A Journey from the Scratch

Background:

Estrogens are essential for the growth of breast cancer in the case of premenopausal as well as in postmenopausal women. However, most of the breast cancer incidences are reported in postmenopausal women and the concurrent risk surges with an increase in age. Since the enzyme aromatase catalyses essential steps in estrogen biosynthesis, Aromatase Inhibitors (AIs) are effective targeted therapy in patients with Estrogen Receptor positive (ER+) breast cancer. AIs are more effective than Selective Estrogen Receptor Modulators (SERMs) because they block both the genomic and nongenomic activities of ER. Till date, first, second and third-generation AIs have been approved by the FDA. The third-generation AIs, viz. Letrozole, Anastrozole, Exemestane, are currently used in the standard treatment for postmenopausal breast cancer.

Methods:

Data were collected from Medline, PubMed, Google Scholar, Science Direct through searching of keywords: ‘aromatase’, ‘aromatase inhibitors’, ‘breast cancer’, ‘steroidal aromatase inhibitors’, ‘non-steroidal inhibitors’ and ‘generations of aromatase inhibitors’.

Results:

In the current scenario of breast cancer chemotherapy, AIs are the most widely used agents which reveal optimum efficacy along with the least side effects. Keeping in view the prominence of AIs in breast cancer therapy, this review covered the detailed description of aromatase including its role in the biosynthesis of estrogen, biochemistry, gene expression, 3D-structure, and information of reported AIs along with their role in breast cancer treatment.

Conclusion:

AIs are the mainstream solution of the ER+ breast cancer treatment regimen with the continuous improvement of human understanding of the importance of a healthy life of women suffering from breast cancer.

Temporal Acute Serum Estradiol and Tumor Necrosis Factor-α Associations and Risk of Death after Severe Traumatic Brain Injury

Severe traumatic brain injury (TBI) activates a robust systemic response that involves inflammatory and other factors, including estradiol (E2), associated with increased deaths. Tumor necrosis factor-alpha (TNFα) is a significant mediator of systemic shock, and it is an extra-gonadal transcription factor for E2 production. The study objectives were to test the hypotheses: (1) a positive feedback relationship exists between acute serum TNFα and E2; and (2) acute concentrations of E2 and TNFα are prognostic indicators of death after severe TBI. This prospective cohort study included N = 157 adults with severe TBI. Serum samples were collected for the first five days post-injury. The TNFα and E2 levels were averaged into two time epochs: first 72 h (T1) and second 72 h post-injury (T2). A cross-lag panel analysis conducted between T1 and T2 TNFα and E2 levels showed significant cross-lag effects: T1 TNFα and T1 E2 were related to T2 E2 and T2 TNFα, respectively. Cox proportional hazards multi variable regression models determined that increases in T1 E2 (hazard ratio [HR] = 1.79, 95% confidence interval [CI]: 1.15, 2.81), but not T2 E2 (HR = 0.91, 95% CI: 0.56, 1.47), were associated with increased risk of death. Increased T2 TNFα (HR = 2.47, 95% CI: 1.35, 4.53), and T1 TNFα (HR = 1.47, 95% CI: 0.99, 2.19), to a lesser degree, were associated with increased risk of death. Relationships of death with T2 TNFα and T1 E2 were mediated partially by cardiovascular, hepatic, and renal dysfunction. Both E2 and TNFα are systemic, reciprocally related biomarkers that may be indicative of systemic compromise and increased risk of death after severe TBI.

miR-326 down-regulate CYP19A1 expression and estradiol-17b production in buffalo granulosa cells through CREB and C/EBP-β

Ovarian granulosa cells, known to be endocrine cells, have well active TLR4-/NFKB signalling mediated innate immune capabilities. We have previously shown that endotoxin not only transiently regulates proinflammatory cytokines but cells become tolerant on repeated exposure to endotoxin and impaired granulosa cells functions, which includes downregulation of CYP19A1 gene. To understand further endotoxin tolerance and impaired granulosa cells function, genome-wide transcriptomic profiling in endotoxin tolerant buffalo granulosa cells (bGCs) identified miR-326 as upregulated amongst top 5 DE miRNAs [unpublished data] and qPCR validation confirmed its upregulation during endotoxin tolerance. In silico analyses showed that miR-326 targets CYP19A1 gene. Therefore, in the present study, we elucidated the role of miR-326 in buffalo granulosa cells (bGCs). We first validated its expression vis-à-vis CYP19A1 gene expression in bGCs, both in vivo and in vitro. Results showed an inverse relationship between miR-326 and CYP19A1 expression. Similarly, transcription factors, known to be involved in CYP19A1 gene regulation, CREB and C/EBP-β expression was also found to be decreased in granulosa cells mimicking pre-ovulatory follicular stage. Further, miR-326 mimic was transfected to bGCs in culture and expression of CYP19A1 and CREB & C/EBP-β and genes encoding other enzymes of steroidogenesis pathway were also analyzed. The present study results showed that miR-326 significantly inhibits the expression of CYP19A1 gene while expression of transcription factors CREB and C/EBP-β was found to be upregulated. The expression of STAR and CYP11A1 was found to be unaffected. To elucidate the molecular mechanism of miR-326 mediated downregulation of CYP19A1, binding analyses of RNA polymerase II and CEBP-β to CYP19A1 gene promoter II was analyzed. The result also showed decreased binding of RNA polymerase II with increased binding of CEBP-β to CYP19A1 gene promoter II in bGCs, transfected with miR-326 as compared to control. In summary, our results suggest that miR-326 upregulate CREB and CREB may activate C/EBP-β and later inhibited the transcription of CYP19A1 and decreased estradiol-17b production. The miR-326 mediated down-regulation of the CYP19A1 gene involving CREB-C/EBP-β can be exploited in developing strategies to attenuate endotoxin-mediated tolerance induced impaired granulosa cells function to ensure proper fertility in females.

Steroidal alkaloids efficient aromatase inhibitors with potential for the treatment of postmenopausal breast cancer

Plant-derived natural products are of great interest due to their diversity in modern drug discovery. Sarcococca saligna has been used for the treatment of different diseases. The present study was aimed at isolating phytochemical constituents including Alkaloid-C (a), Dictyophlebine (b), Sarcovagine-D (c) and Saracodine (d) Holaphylline (e) from Sarcococca saligna to investigate the anticancer effect of these compounds. These compounds were evaluated for inhibition of aromatase enzyme of breast cancer in assistance by molecular docking simulations to understand molecular interaction between the enzyme and ligands. The IC₅₀ values of compound 1 and 5 were found 138.27 ± 0.01 µl and 12.91 ± 0.01 µl, respectively, and both were found active due to their bulky structures in comparison to the active site of aromatase enzyme. The standard drug exemestane showed potent activity in comparison with the test compounds, having IC₅₀ values of 0.052 ± 0.01 µl. Both compounds showed favorable electrostatic interactions with the active site of aromatase enzyme but the shape and steric bulk of the compounds was the limiting factor in their inhibitory effects. New lead compounds could be generated after extensive modifications guided by computational and experimental tools as a possible anticancer agents by targeting aromatase enzyme.

The science of steroids

Steroids are complex lipophilic molecules that have many actions in the body to regulate cellular, tissue and organ functions across the life-span. Steroid hormones such as cortisol, aldosterone, estradiol and testosterone are synthesised from cholesterol in specialised endocrine cells in the adrenal gland, ovary and testis, and released into the circulation when required. Steroid hormones move freely into cells to activate intracellular nuclear receptors that function as multi-domain ligand-dependent transcriptional regulators in the cell nucleus. Activated nuclear receptors modify expression of hundreds to thousands of specific target genes in the genome. Steroid hormone actions in the fetus include developmental roles in the respiratory system, brain, and cardiovascular system. The synthetic glucocorticoid steroid betamethasone is used antenatally to reduce the complications of preterm birth. Development of novel selective partial glucocorticoid receptor agonists may provide improved therapies to treat the respiratory complications of preterm birth and spare the deleterious effects of postnatal glucocorticoids in other organs.

Systemic Estrone Production and Injury-Induced Sex Hormone Steroidogenesis after Severe Traumatic Brain Injury: A Prognostic Indicator of Traumatic Brain Injury-Related Mortality

Extensive pre-clinical studies suggest that sex steroids are neuroprotective in experimental traumatic brain injury (TBI). However, clinical trials involving sex hormone administration have not shown beneficial results, and our observational cohort studies show systemic estradiol (E2) production to be associated with adverse outcomes. Systemic E2 is produced via aromatization of testosterone (T) or reduction of estrone (E1). E1, also produced via aromatization of androstenedione (Andro) and is a marker of T-independent E2 production. We hypothesized that E1 would be (1) associated with TBI-related mortality, (2) the primary intermediate for E2 production, and (3) associated with adipose tissue-specific aromatase transcription. We assessed 100 subjects with severe TBI and 8 healthy controls. Serum levels were measured on days 0-3 post-TBI for key steroidogenic precursors (progesterone), aromatase pathway intermediates (E1, E2, T, Andro), and the adipose tissue-specific aromatase transcription factors cortisol, tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6). E1 was elevated after TBI versus controls. High E1 was associated with higher progesterone, cortisol, and IL-6 (p < 0.05). Multivariable logistic regression demonstrated that those in the highest E1 tertile had increased odds for mortality (adjusted OR = 5.656, 95% CI = 1.102-29.045, p = 0.038). Structural equation models show that early serum E2 production is largely T independent, occurring predominantly through E1 metabolism. Acute serum E1 functions as a mortality marker for TBI through aromatase-dependent E1 production and T-independent E2 production. Further work should evaluate risk factors for high E2 production and how systemic E2 and its key intermediate E1 contribute to the extracerebral consequences of severe TBI.

Effects on the reproductive parameters of two generations of Rattus norvegicus offspring from dams exposed to heptachlor during gestation and lactation

Heptachlor has been targeted for global elimination because of its toxicity and environmental persistence, in accordance with the Stockholm Convention on Persistent Organic Pollutants (POPs). However, there is no regulation of heptachlor use in Mexico, where relatively high levels have been found in maternal breast milk. The aim of this study was to determine the effects of heptachlor on the reproductive system of offspring of two consecutive generations of rats (F1 and F2) from dams orally administered heptachlor during midgestation and lactation. Female offspring were analyzed for different phenotypic, reproductive, and molecular parameters. In the F1 generation, heptachlor treatment induced decreased body weight at weaning, increased female anogenital distance, and delayed vaginal opening. In both generations, serum progesterone levels decreased and estradiol levels remained unchanged, while overexpression of the progesterone receptor was observed in uterine epithelial cells on estrus day. In the F2 generation, expression of the estrogen receptor α increased in the glandular epithelium. Finally, heptachlor treatment did not affect apoptosis in the uterine epithelial cells. Overall, the results indicate that heptachlor induced female reproductive alterations when administered to dams during the perinatal period. Accordingly, exposure to heptachlor may represent a risk for the reproductive health of humans. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 856-868, 2017.

The role of sex hormones and steroid receptors on female reproductive cancers

Sex steroids have been widely described to be associated with a number of human diseases, including hormone-dependent tumors. Several studies have been concerned about the factors regulating the availability of sex steroids and its importance in the pathophysiological aspects of the reproductive cancers in women. In premenopausal women, large fluctuations in the concentration of circulating estradiol (E2) and progesterone (P4) orchestrate many events across the menstrual cycle. After menopause, the levels of circulating E2 and P4 decline but remain at high concentration in the peripheral tissues. Notably, there is a strong relationship between circulating sex hormones and female reproductive cancers (e.g. ovarian, breast, and endometrial cancers). These hormones activate a number of specific signaling pathways after binding either to estrogen receptors (ERs), especially ERα, ERα36, and ERβ or progesterone receptors (PRs). Importantly, the course of the disease will depend on particular transactivation pathway. Identifying ER- or PR-positive tumors will benefit patients in terms of proper endocrine therapy. Based on hormonal responsiveness, effective prevention methods for ovarian, breast, and endometrial cancers represent a special opportunity for women at risk of malignancies. Hormone replacement therapy (HRT) might significantly increase the risk of these cancer types, and endocrine treatments targeting ER signaling may be helpful against E2-dependent tumors. This review will present the role of sex steroids and their receptors associated with the risk of developing female reproductive cancers, with emphasis on E2 levels in pre and postmenopausal women. In addition, new therapeutic strategies for improving the survival rate outcomes in women will be addressed.

Ligand- and Structure-Based Drug Design of Non-Steroidal Aromatase Inhibitors (NSAIs) in Breast Cancer

Aromatase is a multienzyme complex overexpressed in breast cancer and responsible for estrogen production. It is the potential target for designing anti-breast cancer drugs. Ligand and Structure-Based Drug Designing approaches (LBDD and SBDD) are involved in development of active and more specific Nonsteroidal Aromatase Inhibitors (NSAIs). Different LBDD and SBDD approaches are presented here to understand their utility in designing novel NSAIs. It is observed that molecules should possess a five or six membered heterocyclic nitrogen containing ring to coordinate with heme portion of aromatase for inhibition. Moreover, one or two hydrogen bond acceptor features, hydrophobicity, and steric factors may play crucial roles for anti-aromatase activity. Electrostatic, van der Waals, and p-p interactions are other important factors that determine binding affinity of inhibitors. HQSAR, LDA-QSAR, GQSAR, CoMFA, and CoMSIA approaches, pharmacophore mapping followed by virtual screening, docking, and dynamic simulation may be effective approaches for designing new potent anti-aromatase molecules.

Estrogen Metabolite 16α-Hydroxyestrone Exacerbates Bone Morphogenetic Protein Receptor Type II-Associated Pulmonary Arterial Hypertension Through MicroRNA-29-Mediated Modulation of Cellular Metabolism

BACKGROUND

Pulmonary arterial hypertension (PAH) is a proliferative disease of the pulmonary vasculature that preferentially affects women. Estrogens such as the metabolite 16α-hydroxyestrone (16αOHE) may contribute to PAH pathogenesis, and alterations in cellular energy metabolism associate with PAH. We hypothesized that 16αOHE promotes heritable PAH (HPAH) via microRNA-29 (miR-29) family upregulation and that antagonism of miR-29 would attenuate pulmonary hypertension in transgenic mouse models of Bmpr2 mutation.

METHODS AND RESULTS

MicroRNA array profiling of human lung tissue found elevation of microRNAs associated with energy metabolism, including the miR-29 family, among HPAH patients. miR-29 expression was 2-fold higher in Bmpr2 mutant mice lungs at baseline compared with controls and 4 to 8-fold higher in Bmpr2 mice exposed to 16αOHE 1.25 μg/h for 4 weeks. Blot analyses of Bmpr2 mouse lung protein showed significant reductions in peroxisome proliferator-activated receptor-γ and CD36 in those mice exposed to 16αOHE and protein derived from HPAH lungs compared with controls. Bmpr2 mice treated with anti-miR-29 (20-mg/kg injections for 6 weeks) had improvements in hemodynamic profile, histology, and markers of dysregulated energy metabolism compared with controls. Pulmonary artery smooth muscle cells derived from Bmpr2 murine lungs demonstrated mitochondrial abnormalities, which improved with anti-miR-29 transfection in vitro; endothelial-like cells derived from HPAH patient induced pluripotent stem cell lines were similar and improved with anti-miR-29 treatment.

CONCLUSIONS

16αOHE promotes the development of HPAH via upregulation of miR-29, which alters molecular and functional indexes of energy metabolism. Antagonism of miR-29 improves in vivo and in vitro features of HPAH and reveals a possible novel therapeutic target.

Recent developments in steroidal and nonsteroidal aromatase inhibitors for the chemoprevention of estrogen-dependent breast cancer

Aromatase, a cytochrome P450 enzyme complex present in breast tissues, plays a significant role in the biosynthesis of important endogenous estrogens from androgens. The source of estrogen production in breast cancer tissues is intra-tumoral aromatase, and inhibition of aromatase may inhibit the growth stimulation effect of estrogens in breast cancer tissues. Consequently, aromatase is considered a useful therapeutic target in the treatment and prevention of estrogen-dependent breast cancer. Recently, different natural products and synthetic compounds have been rapidly developed, studied, and evaluated for aromatase inhibitory activity. Aromatase inhibitors are classified into two categories on the basis of their chemical structures, i.e., steroidal and nonsteroidal aromatase inhibitors. This review highlights the synthetic steroidal and nonsteroidal aromatase inhibitors reported in the literature in the last few years and will aid medicinal chemists in the design and synthesis of novel and pharmacologically-potent aromatase inhibitors for the treatment of breast cancer.

Genetics of androgen metabolism in women with infertility and hypoandrogenism

Hypoandrogenism in women with low functional ovarian reserve (LFOR, defined as an abnormally low number of small growing follicles) adversely affects fertility. The androgen precursor dehydroepiandrosterone (DHEA) is increasingly used to supplement treatment protocols in women with LFOR undergoing in vitro fertilization. Due to differences in androgen metabolism, however, responses to DHEA supplementation vary between patients. In addition to overall declines in steroidogenic capacity with advancing age, genetic factors, which result in altered expression or enzymatic function of key steroidogenic proteins or their upstream regulators, might further exacerbate variations in the conversion of DHEA to testosterone. In this Review, we discuss in vitro studies and animal models of polymorphisms and gene mutations that affect the conversion of DHEA to testosterone and attempt to elucidate how these variations affect female hormone profiles. We also discuss treatment options that modulate levels of testosterone by targeting the expression of steroidogenic genes. Common variants in genes encoding DHEA sulphotransferase, aromatase, steroid 5α-reductase, androgen receptor, sex-hormone binding globulin, fragile X mental retardation protein and breast cancer type 1 susceptibility protein have been implicated in androgen metabolism and, therefore, can affect levels of androgens in women. Short of screening for all potential genetic variants, hormonal assessments of patients with low testosterone levels after DHEA supplementation facilitate identification of underlying genetic defects. The genetic predisposition of patients can then be used to design individualized fertility treatments.

Ligand- and Structure-Based Drug Design of Non-Steroidal Aromatase Inhibitors (NSAIs) in Breast Cancer

Aromatase is a multienzyme complex overexpressed in breast cancer and responsible for estrogen production. It is the potential target for designing anti-breast cancer drugs. Ligand and Structure-Based Drug Designing approaches (LBDD and SBDD) are involved in development of active and more specific Nonsteroidal Aromatase Inhibitors (NSAIs). Different LBDD and SBDD approaches are presented here to understand their utility in designing novel NSAIs. It is observed that molecules should possess a five or six membered heterocyclic nitrogen containing ring to coordinate with heme portion of aromatase for inhibition. Moreover, one or two hydrogen bond acceptor features, hydrophobicity, and steric factors may play crucial roles for anti-aromatase activity. Electrostatic, van der Waals, and p-p interactions are other important factors that determine binding affinity of inhibitors. HQSAR, LDA-QSAR, GQSAR, CoMFA, and CoMSIA approaches, pharmacophore mapping followed by virtual screening, docking, and dynamic simulation may be effective approaches for designing new potent anti-aromatase molecules.

Impact of obesity on mammary gland inflammation and local estrogen production

Obesity rates have risen dramatically over the past century, having nearly doubled since 1980. Changes in diet and lifestyle have contributed to this occurrence in younger women, and changing hormone levels during the menopausal transition has no doubt exacerbated the issue in older women. The relationship between adiposity and breast cancer is clear in postmenopausal women, and is intimately linked to the increased expression of aromatase and the production of estrogens within the breast adipose. This, in turn, is highly dependent on the localized chronic inflammation observed in obese adipose. This review will therefore explore the relationship between obesity, inflammation and estrogens, with a particular focus on the molecular regulation of aromatase in the postmenopausal breast in the context of obesity and breast cancer.

Sex hormones and breast cancer risk and prognosis

The study of large prospective collections of plasma samples from women prior to the development of breast cancer has firmly established certain sex steroids as being significantly associated with risk. The strongest associations have been found in postmenopausal women in whom the within person variability of most hormones is markedly reduced but some positive associations have also been seen in premenopausal women. Plasma estrogens show the strongest correlations with risk and these are strengthened by measurement or calculation of the proportion of estradiol that circulates free of sex hormone binding globulin (SHBG), consistent with this being the most active fraction. The relationships have been reported to potentially explain virtually all of the association of breast cancer with body mass index in postmenopausal women; this is likely to be due to non-ovarian estrogen synthesis being prominent in subcutaneous fat. These strong relationships have led to plasma and urine estrogen levels being used as intermediate end-points in the search for genes that affect breast cancer risk via their role in steroid disposition. Plasma androgen levels also show a relationship with breast cancer risk that is weakened but not eliminated by 'correction' for estrogen levels. This has been argued to be evidence of the local production of estrogens being important in the etiology of breast cancer. Given that plasma steroid levels do not correlate closely with mammographic density, which is strongly associated with risk, the opportunity exists to combine the two factors in assessing breast cancer risk but the low availability of suitable estrogen assays is a major impediment to this. In established breast cancer, plasma estrogens have been found to correlate with gene expression of estrogen dependent genes and the expression of these varies across the menstrual cycle of premenopausal women. There is infrequently a need for routine measurement of plasma estrogen levels but it has been important in the comparative pharmacology and dose-related effectiveness of aromatase inhibitors. Measurement may be needed to identify residual ovarian function in women who have amenorrhea subsequent to cytotoxic chemotherapy indicating their unsuitability for aromatase inhibitor treatment. Use of highly sensitive assays has also revealed that the association between BMI and plasma estrogen levels persists in patients on 3rd generation aromatase inhibitors and that measurable increments in plasma estrogen levels occur with some vaginal estrogen preparations that are of concern in relation to treatment efficacy.

Tissue-specific regulation of aromatase promoter II by the orphan nuclear receptor LRH-1 in breast adipose stromal fibroblasts

In postmenopausal breast cancers, the increase in aromatase expression observed in tumour associated adipose stromal cells is mediated via the upregulation of promoter II (PII) transcription. Factors such as PGE₂ which are secreted from breast carcinomas induce PII expression. The orphan nuclear receptor LRH-1/NR5A2 is one of the critical downstream transcriptional mediators of this effect. The aim of the current study was to determine whether LRH-1 could bind directly to PII and whether the suppression of LRH-1 expression could inhibit aromatase expression in human adipose stromal fibroblasts. Chromatin immunoprecipitation demonstrated endogenous LRH-1 occupancy on PII under basal conditions and with treatment with forskolin and phorbol 12-myristate 13-acetate (PMA). To assess the impact of LRH-1 knockdown on FSK/PMA mediated PII expression, cells were transfected with shRNA targeted against LRH-1 (shLRH-1) and treated with forskolin and PMA. A decrease in LRH-1, PII and total aromatase mRNA transcripts was observed in shLRH-1 transfected cells compared to controls under basal and treatment conditions. The results of this study support the hypothesis that suppression of LRH-1 may potentially be beneficial in the tissue specific regulation of aromatase expression in post menopausal breast cancer.

Megestrol acetate inhibits the expression of cytoplasmic aromatase through nuclear C/EBPβ in reperfusion injury-induced ischemic rat hippocampus

Global ischemia after cardiac arrest, intraoperative hypoxia/hypotension, and hemorrhagic shock causes brain injury resulting in severe neurological and neurobehavioral deficits. Neurodegeneration can be prevented by local aromatase expression, and estrogen synthesis can be neuroprotective in ischemia/reperfusion. Therefore, aromatase, the enzyme that transforms androgens to estrogens, may be a potential target for the study of reperfusion injury after brain ischemia. We investigated the expression of aromatase and C/EBPβ using western blotting in rat hippocampus after transient global ischemia plus hypotension. Immunohistochemical analysis was performed for aromatase. After 10min of ischemia, aromatase and C/EBPβ expression in cytosolic extracts were observed after 10min and 24h of reperfusion. The expression of both proteins was similar in control and damaged tissues. Immunoblot analysis demonstrated that the highest aromatase expression appeared in damaged hippocampi after 1week and was gradually reduced after 2-10weeks. C/EBPβ expression increased at 1week in nuclear extracts of damaged hippocampi. The aromatase inhibitor megestrol acetate (20mg/kg/day) suppressed aromatase and nuclear C/EBPβ levels in ischemic hippocampi. Our findings indicate that ischemia as well as chronic neurodegenerative processes leads to an increase in cytoplasmic aromatase and nuclear C/EBPβ. Thus, it is possible to hypothesize an interaction between this enzyme gene and transcription factor.

The mechanism of sex determination in vertebrates-are sex steroids the key-factor?

In many vertebrate species, sex is determined at fertilization of zygotes by sex chromosome composition, knows as genotypic sex determination (GSD). But in some species-fish, amphibians and reptiles-sex is determined by environmental factors; in particular by temperature-dependent sex determination (TSD). However, little is known about the mechanisms involved in TSD and GSD. How does TSD differ from GSD? As is well known, genes that activated downstream of sex-determining genes are conserved throughout all classes of vertebrates. What is the main factor that determines sex, then? Sex steroids can reverse sex of several species of vertebrate; estrogens induce the male-to-female sex-reversal, whereas androgens do the female-to-male sex-reversal. For such sex-reversal, a functioning sex-determining gene is not required. However, in R. rugosa CYP19 (P450 aromatase) is expressed at high levels in indifferent gonads before phenotypic sex determination, and the gene is also active in the bipotential gonad of females before sex determination. Thus, we may predict that an unknown factor, a common transcription factor locates on the X and/or W chromosome, intervenes directly or indirectly in the transcriptional up-regulation of the CYP19 gene for feminization in species of vertebrates with both TSD and GSD. Similarly, an unknown factor on the Z and/or Y chromosome probably intervenes directly or indirectly in the regulation of androgen biosynthesis for masculinization. In both cases, a sex-determining gene is not always necessary for sex determination. Taken together, sex steroids may be the key-factor for sex determination in some species of vertebrates.

Influence of Sex Hormones on Cancer Progression

To review the influence of sex hormones on the progression of breast, prostate, gynecologic, and colorectal cancer. The literature was reviewed in an informal manner utilizing the authors' prior knowledge to collate the current evidence for the involvement of sex hormones, particularly estrogens and androgens in the progression of a range of hormonally responsive cancers. In particular, the effect of treatment involving hormone withdrawal treatment was considered strong evidence for involvement. The impact of basal levels of endogenous steroids was considered. Data from clinical trials indicate the efficacy of therapeutic interventions that result in ablation or antagonism of host steroids for a range of cancers. Demonstration of the correlation of the completeness of withdrawal with clinical outcome together with direct evidence of progression from studies looking at the influence of tissue and circulating levels of sex hormones more recently in conjunction with gene expression profiles all provide compelling evidence for the involvement of steroids in the progression of disease. The involvement of steroids in the progression of cancer in hormone-sensitive tissues is well established and an important target for therapy.

The multiple roles of estrogens and the enzyme aromatase

Aromatase is the enzyme that catalyzes the last step of estrogen biosynthesis. It is expressed in many tissues such as the gonads, brain and adipose tissue. The regulation of the level and activity of aromatase determines the levels of estrogens that have endocrine, paracrine and autocrine effects on tissues. Estrogens play many roles in the body, regulating reproduction, metabolism and behavior. In the brain, cell survival and the activity of neurons are affected by estrogens and hence aromatase.

Mechanism-based categorization of aromatase inhibitors: a potential discovery and screening tool

Cytochrome P450 aromatase is a key steroidogenic enzyme that converts androgens to estrogens in vertebrates. There is much interest in aromatase inhibitors (AIs) both because of their use as pharmaceuticals in the treatment of estrogen-sensitive breast cancers, and because a number of environmental contaminants can act as AIs, thereby disrupting endocrine function in humans and wildlife through suppression of circulating estrogen levels. The goal of the current work was to develop a mechanism-based structure-activity relationship (SAR) categorization framework highlighting the most important chemical structural features responsible for inhibition of aromatase activity. Two main interaction mechanisms were discerned: steroidal and non-steroidal. The steroid scaffold is most prominent when the structure of the target chemical is similar to the natural substrates of aromatase - androstenedione and testosterone. Chemicals acting by non-steroidal mechanism(s) possess a heteroatom (N, O, S) able to coordinate the heme iron of the cytochrome P450, and thus interfere with steroid hydroxylation. The specific structural boundaries controlling AI for both analyzed mechanisms were defined, and a software tool was developed that allowed a decision tree (profile) to be built discriminating AIs by mechanism and potency. An input chemical follows a profiling path and the structure is examined at each step to decide whether it conforms with the structural boundaries implemented in the decision tree node. Such a system would aid drug discovery efforts, as well as provide a screening tool to detect environmental contaminants that could act as AIs.

Aromatase expression is increased in BRCA1 mutation carriers

BACKGROUND

Until recently, the molecular mechanisms explaining increased incidence of ovarian and breast cancers in carriers of BRCA1 gene mutations had not been clearly understood. Of significance is the finding that BRCA1 negatively regulates aromatase expression in vitro. Our objective was to characterise aromatase gene (CYP19A1) and its promoter expression in breast adipose and ovarian tissue in BRCA1 mutation carriers and unaffected controls.

METHODS

We measured aromatase transcripts, total and promoter-specific (PII, PI.3, PI.4) in prophylactic oophorectomy or mastectomy, therapeutic mastectomy, ovarian and breast tissue from unaffected women.

RESULTS

We demonstrate that the lack of functional BRCA1 protein correlates to higher aromatase levels in 85% of BRCA1 mutation carriers. This increase is mediated by aberrant transcriptional regulation of aromatase; in breast adipose by increases in promoter II/I.3 and I.4-specific transcripts; and in the ovary with elevation in promoter I.3 and II-specific transcripts.

CONCLUSION

Understanding the link between BRCA1 and aromatase is significant in terms of understanding why carcinogenesis is restricted to estrogen-producing tissues in BRCA1 mutation carriers.

The soy isoflavone genistein induces estrogen synthesis in an extragonadal pathway

Genistein is a phytoestrogen isolated from soyabean, and is a potential nutraceutical gearing for women suffering from perimenopausal symptoms. Because of its differential binding affinity to estrogen receptor (ER) isoforms, genistein is described as a selective estrogen receptor modulator (SERM). The ligand-receptor interaction is established, but the potential confounding factors have not been fully addressed. Alteration in estrogen metabolism is an important issue when determining the downstream effect of ER. Aromatase or CYP19 catalyzes the rate-limiting reaction of estrogen synthesis, and is highly expressed in the ovary. This organ is the source of estrogen in females. After menopause the ovaries cease to produce the hormone, and localized estrogen synthesis in extragonadal tissues could become physiologically significant. In the present study, effect of genistein on CYP19 regulation was investigated in the hepatic cells HepG2. The phytoestrogen induced aromatase activity in the cells. Increased mRNA expression with concurrent elevation in the usage of promoters I.3/II was also demonstrated. Luciferase reporter gene assays verified the transcriptional control dictated by the specific promoters under genistein treatment. Several protein kinases were examined, and PKC?, P38, ERK-1/2 appeared to be activated. Subsequent inhibition and expression experiments demonstrated the involvement of these kinases. The transcriptional factor CREB was ultimately activated in the gene regulation. The present study illustrated an extragonadal pathway by which genistein might increase estrogen synthesis.

The Coffey Lecture: steroidogenic enzyme inhibitors and hormone dependent cancer

OBJECTIVES

To improve treatment for patients with breast and prostate cancer.

METHODS

A number of novel inhibitors of steroidogenic enzymes have been developed. Their biological effects have been evaluated in a variety of preclinical models. Aromatase (estrogen synthetase) inhibitors have now been extensively tested in clinical trials in breast cancer patients. Inhibitors of 17alpha-hydroxylase/lyase have also been studied in preclinical models and are beginning trials in prostate cancer patients.

RESULTS

The enzyme aromatase (CYP19) has proven to be an important therapeutic target. Inhibitors of aromatase (AIs) are showing greater benefit than antiestrogens in the treatment of breast cancer. Although effective in other conditions in both women and men, AIs have not been useful in benign prostatic hypertrophy or prostate cancer. However inhibitors of 17alphahydroxylase/lyase (CYP17) to block synthesis of androgens may be effective for prostate cancer. Recent clinical trials with abiraterone and preclinical studies with other novel CYP17 inhibitors, which also interact with the androgen receptor and cause its down-regulation, could provide a new approach for treating this disease. In further studies, we optimized treatment with aromatase inhibitors and antiestrogens utilizing an intratumoral aromatase xenograft model. AIs were more effective and sustained growth inhibition was longer than antiestrogens. However, inevitably tumors eventually began to grow despite continued treatment. Analysis of breast tumors from mice treated with letrozole revealed up-regulation of HER-2 and MAP Kinase signaling proteins and down-regulation of the estrogen receptor. Our studies showed that tumors adapt to AI treatment by activating alternate signaling pathways, thus enabling them to proliferate in the absence of estrogen. When mice bearing resistant tumors were treated with trastuzumab, the anti-HER-2 antibody (herceptin), HER-2 was decreased in the tumor but the estrogen receptor and aromatase were restored. Tumor growth was significantly inhibited by treatment with trastuzumab in addition to letrozole.

CONCLUSIONS

Aromatase inhibitors are proving to be an effective new class of agents for the treatment of breast cancer. Compounds inhibiting 17alphahydroxylase/lyase have potential for the treatment of prostate cancer. Our results suggest that strategies to overcome resistance to these types of agents can restore sensitivity of the tumors to hormone therapy.

Sex determination in amphibians

The heterogametic sex is male in all mammals, whereas it is female in almost all birds. By contrast, there are two heterogametic types (XX/XY and ZZ/ZW) for genetic sex determination in amphibians. Though the original heterogametic sex was female in amphibians, the two heterogametic types were probably interchangeable, suggesting that sex chromosomes evolved several times in this lineage. Indeed, the frog Rana rugosa has the XX/XY and ZZ/ZW sex-determining systems within a single species, depending on the local population in Japan. The XY and ZW geographic forms with differentiated sex chromosomes probably have a common origin as undifferentiated sex chromosomes resulted from the hybridization between the primary populations of West Japan and Kanto forms. It is clear that the sex chromosomes are still undergoing evolution in this species group. Regardless of the presence of a sex-determining gene in amphibians, the gonadal sex of some species can be changed by sex steroids. Namely, sex steroids can induce the sex reversal, with estrogens inducing the male-to-female sex reversal, whereas androgens have the opposite effect. In R. rugosa, gonadal activity of CYP19 (P450 aromatase) is correlated with the feminization of gonads. Of particular interest is that high levels of CYP19 expression are observed in indifferent gonads at time before sex determination. Increases in the expression of CYP19 in female gonads and CYP17 (P450 17alpha-hydroxylase/C17-20 lyase) in male gonads suggest that the former plays an important role in phenotypic female determination, whereas the latter is needed for male determination. Thus, steroids could be the key factor for sex determination in R. rugosa. In addition to the role of sex steroids in gonadal sex determination in this species, Foxl2 and Sox3 are capable of promoting CYP19 expression. Since both the genes are autosomal, another factor up-regulating CYP19 expression must be recruited. The factor, which may be located on the X or W chromosome, intervenes directly or indirectly, in the transcriptional regulation of the CYP19 gene for feminization in amphibians. A factor up-regulating CYP17 expression remains to be identified.

Genetic polymorphisms and endometrial cancer risk

For most sporadic cancers, genetic susceptibility results from the additive effect of multiple genetic variants, each of which contributes a modest risk individually. The study of genetic single nucleotide polymorphisms (SNPs) may help explain the differences in individual cancer susceptibility and may assist in identifying novel markers of risk that can be utilized to create more effective and tailored cancer prevention strategies. Genetic polymorphisms in functionally critical genes have been suggested as risk factors for the development of a variety of cancers, including endometrial cancer. Candidate SNPs may be involved in DNA damage repair, steroid metabolism, carcinogen metabolism, cell-cycle control, apoptosis and steroid receptor activation pathways. In this review, recent findings of genetic association studies exploring genetic polymorphisms and their association with endometrial cancer are reported. In addition, the challenges of genetic association studies, such as power and bias, and the need for validation of promising findings are explored.

Synthesis and biological evaluation of 3-(azolylmethyl)-1H-indoles and 3-(alpha-azolylbenzyl)-1H-indoles as selective aromatase inhibitors

This present study identifies a number of azolyl-substituted indoles as potent inhibitors of aromatase. In the sub-series of 3-(azolylmethyl)-1H-indoles, four imidazole derivatives and their triazole analogues were tested. Imidazole derivatives 11 and 14 in which the benzyl moiety was substituted by 2-chloro and 4-cyano groups, respectively, were the most active, with IC50 values ranging between 0.054 and 0.050 microM. In the other sub-series, eight 3-(alpha-azolylbenzyl)-1H-indoles were prepared and tested. Compound 30, the N-ethyl imidazole derivative, proved to be an aromatase inhibitor, showing an IC50 value of 0.052 microM. All target compounds were further evaluated against 17alpha-hydroxylase/C17,20-lyase to determine their selectivity profile.

Inflammatory status influences aromatase and steroid receptor expression in endometriosis

Aberrant up-regulation of aromatase in eutopic endometrium and implants from women with endometriosis has been reported. Aromatase induction may be mediated by increased cyclooxygenase-2 (COX-2). Recently, we demonstrated that progesterone receptor (PR)-A and PR-B serve an antiinflammatory role in the uterus by antagonizing nuclear factor kappaB activation and COX-2 expression. PR-C, which antagonizes PR-B, is up-regulated by inflammation. Although estrogen receptor alpha (ERalpha) is implicated in endometriosis, an antiinflammatory role of ERbeta has been suggested. We examined stage-specific expression of aromatase, COX-2, ER, and PR isoform expression in eutopic endometrium, implants, peritoneum, and endometrioma samples from endometriosis patients. Endometrial and peritoneal biopsies were obtained from unaffected women and those with fibroids. Aromatase expression in eutopic endometrium from endometriosis patients was significantly increased compared with controls. Aromatase expression in endometriosis implants was markedly increased compared with eutopic endometrium. Aromatase mRNA levels were increased significantly in red implants relative to black implants and endometrioma cyst capsule. Moreover, COX-2 expression was increased in implants and in eutopic endometrium of women with endometriosis as compared with control endometrium. As observed for aromatase mRNA, the highest levels of COX-2 mRNA were found in red implants. The ratio of ERbeta/ERalpha mRNA was significantly elevated in endometriomas compared with endometriosis implants and eutopic endometrium. Expression of PR-C mRNA relative to PR-A and PR-B mRNA was significantly increased in endometriomas compared with eutopic and control endometrium. PR-A protein was barely detectable in endometriomas. Thus, whereas PR-C may enhance disease progression, up-regulation of ERbeta may play an antiinflammatory and opposing role.

Molecular characterization of the injury-induced aromatase transcript in the adult zebra finch brain

In the zebra finch (Taeniopygia guttata), the aromatase gene is transcribed from one of two promoters resulting in two transcripts constitutively expressed in brain or ovary. These transcripts differ only in Exon 1 which lies in the 5' un-translated region (UTR). An inducible form of aromatase is expressed following brain injury in glia. Towards characterizing this transcript, we (a) examined the up-regulation of amplicons within the aromatase transcript using quantitative PCR (qPCR), (b) performed 5' and 3' rapid amplification of cDNA ends (RACE) on injured brain RNA and (c) sequenced the injury-induced aromatase transcript. qPCR suggested that inducible aromatase may contain a novel 3'UTR. However, neither 3' nor 5' RACE revealed novel UTRs in the injured telencephalon. We then sequenced aromatase from injured entopallium, a region that lacks detectable constitutive aromatase. Inducible aromatase was identical in sequence to the known neural aromatase transcript. These data suggest that injury-induced aromatase differs from ovarian, but is indistinguishable from neuronal aromatase. We suggest that an injury-specific signal in glia may modulate aromatase transcription. Alternatively, injury-induced aromatase transcription may be silenced under constitutive conditions. To the best of our knowledge, this is the first report that documents the sequence of inducible aromatase in any vertebrate.

Pharmacological concentration of resveratrol suppresses aromatase in JEG-3 cells

Estrogen is crucial in preparing of pregnancy, and its role in the maintenance of pregnancy has yet to be elucidated. During the course of pregnancy, the placenta is responsible for the provision of estrogen. The hormone biosynthesis is catalyzed by cytochrome P450 (CYP) 19 or aromatase. In the present study, we screened several common dietary components and identified the grape polyphenol resveratrol to be a potential inhibitor in the hormone synthesis. In a recombinant protein system resveratrol inhibited the aromatase activity with an IC(50) value of approximately 40 microM. Subsequent analysis was performed in the human placental JEG-3 cells, and 25 microM resveratrol significantly reduced the mRNA abundance in these cells. Since the transcriptional control of CYP19 gene is tissue-specific and the proximal promoter region of exon Ia has previously been shown to be crucial in CYP19 expression in placental cells, we also evaluated the promoter activity of this gene. Reporter gene assays revealed that resveratrol repressed the transcriptional control of promoter Ia. The present study illustrated the possibility that dietary supplementation of resveratrol interfered with the normal functioning of placental cells.

Aromatase and COX in breast cancer: enzyme inhibitors and beyond

Aromatase expression and enzyme activity in breast cancer patients is greater in or near the tumor tissue compared with the normal breast tissue. Complex regulation of aromatase expression in human tissues involves alternative promoter sites that provide tissue-specific control. Previous studies in our laboratories suggested a strong association between aromatase (CYP19) gene expression and the expression of cyclooxygenase (COX) genes. Additionally, nonsteroidal anti-inflammatory drugs (NSAIDs) and COX selective inhibitors can suppress CYP19 gene expression and decrease aromatase activity. Our current hypothesis is that pharmacological regulation of aromatase and/or cyclooxygenases can act locally to decrease the biosynthesis of estrogen and may provide additional therapy options for patients with hormone-dependent breast cancer. Two pharmacological approaches are being developed, one involving mRNA silencing by selective short interfering RNAs (siRNA) molecules and the second utilizing small molecule drug design. In the first approach, short interfering RNAs were designed against either human aromatase mRNA or human COX-2 mRNA. Treatment of breast cancer cells with siAROMs completely masked the aromatase enzyme activity. Treatment with COX-2 siRNAs decreased the expression of COX-2 mRNA; furthermore, the siCOX-2-mediated decrease also resulted in suppression of CYP19 mRNA. The small molecule drug design approach focuses on the synthesis and biological evaluation of a novel series of sulfonanilide analogs derived from the COX-2 selective inhibitors. The compounds suppress aromatase enzyme activity in SK-BR-3 breast cancer cells in a dose and time-dependent manner, and structure activity analysis does not find a correlation between aromatase suppression and COX inhibition. Real-time PCR analysis demonstrates that the sulfonanilide analogs decrease aromatase gene transcription in breast cells. Thus, these results suggest that the siRNAs and novel sulfonanilides targeting aromatase expression may be valuable tools for selective regulation of aromatase in breast cancer.

Chemoprevention of breast cancer with selective oestrogen-receptor modulators

Twenty years ago, a new therapeutic dimension was conceived that not only had the potential to treat and prevent osteoporosis, but to prevent breast and endometrial cancer at the same time. As osteoporosis was known to be caused by oestrogen withdrawal after menopause, whereas breast and endometrial cancer are caused by unopposed oestrogen action, the new tissue-selective oestrogens and anti-oestrogens, or selective oestrogen-receptor modulators (SERMs), had to recruit new networks to activate or suppress target tissues selectively. New medicines now promise to provide chemoprevention strategies for women at risk for the development of many diseases.

Development and evolution of therapies targeted to the estrogen receptor for the treatment and prevention of breast cancer

This article describes the origins and evolution of "antiestrogenic" medicines for the treatment and prevention of breast cancer. Developing drugs that target the estrogen receptor (ER) either directly (tamoxifen) or indirectly (aromatase inhibitors) has improved the prognosis of breast cancer and significantly advanced healthcare. The development of the principles for treatment and the success of the concept, in practice, has become a model for molecular medicine and presaged the current testing of numerous targeted therapies for all forms of cancer. The translational research with tamoxifen to target the ER with the appropriate duration (5 years) of adjuvant therapy has contributed to the falling national death rates from breast cancer. Additionally, exploration of the endocrine pharmacology of tamoxifen and related nonsteroidal antiestrogen (e.g. keoxifene now known as raloxifene) resulted in the laboratory recognition of selective ER modulation and the translation of the concept to use raloxifene for the prevention of osteoporosis and breast cancer. However, the extensive evaluation of tamoxifen treatment revealed small but significant side effects such as endometrial cancer, blood clots and the development of acquired resistance. The solution was to develop drugs that targeted the aromatase enzyme specifically to prevent the conversion of androstenedione to estrone and subsequently estradiol. The successful translational research with the suicide inhibitor 4-hydroxyandrostenedione (known as formestane) pioneered the development of a range of oral aromatase inhibitors that are either suicide inhibitors (exemestane) or competitive inhibitors (letrozole and anastrozole) of the aromatase enzyme. Treatment with aromatase inhibitors is proving effective and is associated with reduction in the incidence of endometrial cancer and blood clots when compared with tamoxifen and there is also limited cross resistance so treatment can be sequential. Current clinical trials are addressing the value of aromatase inhibitors as chemopreventive agents for postmenopausal women.

Modulation of aromatase activity and mRNA by various selected pesticides in the human choriocarcinoma JEG-3 cell line

Aromatase enzyme plays a central role in steroidogenesis by converting androgens to estrogens and has been proposed as an important molecular target for many environmental endocrine disrupters chemicals. In this study, we have screened 30 selected pesticides with known, unknown or supposed effects on aromatase activity, for their ability to modulate aromatase activity in the human choriocarcinoma JEG-3 cell line after both short (2 h) and long exposure (24 h). All pesticides were tested at concentrations up to 10 microM that did not cause cytotoxicity after 24h of exposure, as verified by the MTT viability assay. Four pesticides inhibited aromatase activity after 2 h of exposure: prochloraz (IC(50)<1 microM), fenbuconazole (IC(50)=1.1 microM), propiconazole (IC(50)=1.5 microM) and fenarimol (IC(50)=3.3 microM). Among them, prochloraz and fenbuconazole also exerted inhibitory effects after 24h. Toxaphen (10 microM) and heptachlor (10 microM) inhibited aromatase activity after 24h exposure only. Nine pesticides induced aromatase activity: aldrin, chlordane, cypermethrin, parathion-methyl, endosulfan, methoxychlor, oxadiazon, metolachlor and atrazine after 24 h of exposure, while tributyltin induced aromatase activity at 1 nM and 3 nM after both 2 h and 24 h of exposure, respectively. To further investigate the mechanisms of aromatase induction we measured CYP19 mRNA expression and showed that methoxychlor, aldrin, chlordane and tributyltin induced the transcription of the cyp19 gene. In addition, none of the aromatase inducers transactivated the retinoic acid receptor (RAR) in JEG-3 stably transfected with a RARE-luciferase plasmid while the RAR agonist TTNPB induced both aromatase and luciferase expression in these cells. Our results, which provide new data for fenbuconazole, as an inhibitor of human aromatase, and for eight pesticides as aromatase inducers, are discussed with regards to the regulation of aromatase expression in the JEG-3 cellular context.

Update on the use of aromatase inhibitors in breast cancer

Estrogens are biosynthesised from androgens by the CYP450 enzyme complex called aromatase. Aromatase is expressed in the ovary, placenta, brain, bone, adipose tissue and breast tissue. In breast cancer, intratumoural aromatase is the source for local estrogen production in the tissue. Inhibition of aromatase is an important approach for reducing growth stimulatory effects of estrogens in estrogen-dependent breast cancer. The potent and selective third-generation aromatase inhibitors anastrozole, letrozole and exemestane were introduced to the market as endocrine therapy in postmenopausal patients failing anti-estrogen therapy alone, or multiple hormonal therapies. Anastrozole and letrozole are both non-steroidal aromatase inhibitors that compete with the substrate for binding to the enzyme active site. Exemestane is a mechanism-based steroidal inhibitor that mimics the substrate, is converted by the enzyme to a reactive intermediate, and results in inactivation of aromatase. These third-generation aromatase inhibitors are currently approved as first-line therapy for the treatment of postmenopausal women with metastatic estrogen-dependent breast cancer. The use of an aromatase inhibitor as initial therapy, or after treatment with tamoxifen, is now recommended as adjuvant hormonal therapy for postmenopausal women with hormone-dependent breast cancer. Several clinical studies of aromatase inhibitors focus on the use of these agents in the adjuvant setting, for the treatment of early breast cancer. Recently published results show improved responses with these agents compared with tamoxifen.

Polymorphisms of estrogen-biosynthesis genes CYP17 and CYP19 may influence age at menarche: a genetic association study in Caucasian females

Variation in age at menarche (AAM) is known to be substantially influenced by genetic factors, but the true causal genes remain largely unidentified. Because the increased amplitude of estrogen exposure of tissues initiates the onset of menarche, the genes involved in estrogen biosynthesis are natural candidate genes underlying AAM. Our study aimed to identify whether the CYP17 and CYP19, the two key genes involved in the biosynthesis of estrogen, are associated with AAM variation in 1048 females from 354 Caucasian nuclear families. We genotyped 38 SNPs and established the linkage disequilibrium blocks and haplotype structures that covered the full transcript length of those two genes. Family-based and population-based statistical analyses were used to test for associations with all of the single SNPs and haplotypes. Both methods consistently detected significant associations for five SNPs of CYP19 with AAM. Haplotype analyses corroborated our single-SNP results by showing that the haplotypes in block 1 were highly significant to AAM in population-based analyses. However, we could not find any association of CYP17 with AAM. Our study is the first to suggest the important effect of CYP19 on AAM variation in Caucasian females. It will be valuable to replicate and confirm these findings in other independent studies, aiming at eventually finding the hidden genetic mechanisms underlying the variation in AAM.

The role of aromatase and 17-β-hydroxysteroid dehydrogenase type 1 mRNA expression in predicting the clinical outcome of human breast cancer

INTRODUCTION

There is substantial evidence that breast cancer tissue contains all the enzymes responsible for the local biosynthesis of estrogens from circulating precursors. The cytochrome P-450 aromatase enzyme complex is responsible for the conversion of C19 androgens to estrogens and 17-beta-hydroxysteroid dehydrogenase (17-I(2)-HSD) type 1 catalyses the inter-conversion of estrone to the biologically more potent estradiol. The gene encoding for the cytochrome P-450 aromatase is known as CYP19 (15q21.2). It is well established that increased exposure to local estrogens is an important risk factor in the genesis and growth of breast cancer. The aim of this study is to investigate the relationship between CYP19 and 17-beta-HSD type 1A mRNA expression and clinico-pathological parameters of human breast cancer.

METHODS

One hundred and twenty seven tumor tissues and 33 normal tissues were analyzed. The levels of transcription of CYP19 and 17-beta-HSD type 1 were determined using real-time quantitative PCR. The mRNA expression was normalized against CK19. Levels of expression were analyzed against tumorâ's stage, grade, nodal status, local relapse, distant metastasis and survival over a 120A months follow up period. In addition, the levels were analyzed against estrogen receptor (ER) and HER1-4 status.

RESULTS

Overall, high tumor levels of mRNA expression of CYP19 and 17-beta-HSD type 1 correlated with poor survival (p=0.0105 and p=0.0182, respectively). Increased levels of CYP19 mRNA expression positively correlated with disease progression as levels were significantly higher in samples of patients who had distant metastasis and local recurrence and/or died of breast related causes when compared to those who were disease free for >10 years (p=0.0015). We also observed higher levels of CYP19 mRNA in tumor samples compared to normal breast tissue. However, this reached statistical significance only when comparing grade 1 tumors with normal tissue (p=0.01). There was no correlation between CYP19á mRNA expression and tumor stage, lymph node status and tumor grade. There was however a trend for a positive correlation between CYP19 and ER mRNA expressions (p=0.06). No significant difference in 17-beta-HSD type 1 expression between normal and cancerous tissues was observed. In tumor samples, we observed an increase in levels correlating with tumor's grade. This correlation was statistically significant when we compared grade 1 with grade 2 and grade 1 with grade 3 (p=0.0031 and 0.0251, respectively).

CONCLUSION

Our study shows that higher levels of the enzymes responsible for the local biosynthesis of estrogens especially aromatase are associated with a poor clinical outcome in patients with breast cancer.

CYP19 (aromatase) haplotypes and endometrial cancer risk

Endogenous estrogen exposure is an important determinant of endometrial cancer risk. Aromatase, encoded by CYP19, catalyzes the aromatization of androstenedione and testosterone to estrone and estradiol, respectively. Several common genetic polymorphisms in CYP19 have been identified, including a TCT insertion/deletion and a (TTTA)(n) repeat polymorphism in intron IV as well as a 3'UTR C/T polymorphism. We evaluated these 3 polymorphisms plus an additional 9 noncoding polymorphisms as individual genotypes and predicted haplotypes as risk factors for endometrial cancer using a nested case-control study design. Invasive endometrial cancer cases (n = 222) and matched controls (n = 666) were identified among participants in the Nurses' Health Study who had provided a blood sample in 1989-1990 (n = 32,826). We estimated haplotypes from unphased genotype data spanning > 123 kb of CYP19. Six haplotypes constructed from 10 SNPs were estimated with a frequency > or = 5%. The highest prevalence haplotype (33% among cases, 28% among controls) was significantly associated with endometrial cancer risk (p = 0.03). Loci with variant alleles that comprise the risk haplotype were independently associated with endometrial cancer, with relative risk estimates ranging from 1.68 (95% CI 1.13-2.48) to 2.07 (95% CI 1.33-3.23), comparing variant allele carriers to wild-type homozygotes. We observed significant interactions between menopausal status and 2 of the high-risk loci (p = 0.03 and p < 0.01), with > 2-fold increased risk for variant allele carriers who were postmenopausal but no association between genotype and endometrial cancer among premenopausal women. We evaluated associations between CYP19 haplotypes and plasma steroid hormone levels. The haplotype associated with endometrial cancer risk is also significantly associated with the ratios of estrone to androstenedione and estradiol to testosterone, the products and substrates of the enzyme aromatase, encoded by CYP19. Our data suggest that there is a high-frequency CYP19 haplotype related to higher estrogen to androgen ratios and increased risk of endometrial cancer and that this association may primarily pertain to postmenopausal women.

Aromatase inhibitors in the treatment of breast cancer

Estradiol, the most potent endogenous estrogen, is biosynthesized from androgens by the cytochrome P450 enzyme complex called aromatase. Aromatase is present in breast tissue, and intratumoral aromatase is the source of local estrogen production in breast cancer tissues. Inhibition of aromatase is an important approach for reducing growth-stimulatory effects of estrogens in estrogen-dependent breast cancer. Steroidal inhibitors that have been developed to date build upon the basic androstenedione nucleus and incorporate chemical substituents at varying positions on the steroid. Nonsteroidal aromatase inhibitors can be divided into three classes: aminoglutethimide-like molecules, imidazole/triazole derivatives, and flavonoid analogs. Mechanism-based aromatase inhibitors are steroidal inhibitors that mimic the substrate, are converted by the enzyme to a reactive intermediate, and result in the inactivation of aromatase. Both steroidal and nonsteroidal aromatase inhibitors have shown clinical efficacy in the treatment of breast cancer. The potent and selective third-generation aromatase inhibitors, anastrozole, letrozole, and exemestane, were introduced into the market as endocrine therapy in postmenopausal patients failing antiestrogen therapy alone or multiple hormonal therapies. These agents are currently approved as first-line therapy for the treatment of postmenopausal women with metastatic estrogen-dependent breast cancer. Several clinical studies of aromatase inhibitors are currently focusing on the use of these agents in the adjuvant setting for the treatment of early breast cancer. Use of an aromatase inhibitor as initial therapy or after treatment with tamoxifen is now recommended as adjuvant hormonal therapy for a postmenopausal woman with hormone-dependent breast cancer.

Characterization and expression pattern of zebrafish Anti-Müllerian hormone (Amh) relative to sox9a, sox9b, and cyp19a1a, during gonad development

The role of Anti-Müllerian hormone (Amh) during gonad development has been studied extensively in mammals, but is less well understood in other vertebrates. In male mammalian embryos, Sox9 activates expression of Amh, which initiates the regression of the Mullerian ducts and inhibits the expression of aromatase (Cyp19a1), the enzyme that converts androgens to estrogens. To better understand shared features of vertebrate gonadogenesis, we cloned amh cDNA from zebrafish, characterized its genomic structure, mapped it, analyzed conserved syntenies, studied its expression pattern in embryos, larvae, juveniles, and adults, and compared it to the expression patterns of sox9a, sox9b and cyp19a1a. We found that the onset of amh expression occurred while gonads were still undifferentiated and sox9a and cyp19a1a were already expressed. In differentiated gonads of juveniles, amh showed a sexually dimorphic expression pattern. In 31 days post-fertilization juveniles, testes expressed amh and sox9a, but not cyp19a1a, while ovaries expressed cyp19a1a and sox9b, but not amh. In adult testes, amh and sox9a were expressed in presumptive Sertoli cells. In adult ovaries, amh and cyp19a1a were expressed in granulosa cells surrounding the oocytes, and sox9b was expressed in a complementary fashion in the ooplasm of oocytes. The observed expression patterns of amh, sox9a, sox9b, and cyp19a1a in zebrafish correspond to the patterns expected if their regulatory interactions have been conserved with mammals. The finding that zebrafish sox9b and sox8 were not co-expressed with amh in oocytes excludes the possibility that amh expression in zebrafish granulosa cells is directly regulated by either of these two genes.

Analysis of zebrafish cyp19 promoters

Cyp19 encodes P450 aromatase, the key enzyme catalyzing the conversion of androgens into estrogens. Estrogens play a crucial role in the anatomical, functional and behavioral characteristics of sexually dimorphic development. In zebrafish, two cyp19 genes, cyp19a and cyp19b, expressed in ovary and brain, respectively, were found. We have isolated the promoter regions of the zebrafish cyp19 genes from a bacterial artificial chromosome library to search for regulatory sequences that bind to transcription factors. Sequences like arylhydrocarbon receptor (AhR) recognition site, estrogen receptor recognition half sites (1/2ERE) and c-AMP responsive elements were found in the 5'-flanking regions of both cyp19 genes. For ovarian-specific expression, we found binding sites for steroidogenic factor-1 (SF-1), GATA transcription factor 4 (GATA-4) and Wilm tumor 1 (WT1-KTS) on the promoter region of cyp19a but not cyp19b. For brain-specific expression of the cyp19b gene, sequences for recognition of chicken ovalbumin upstream promoter-transcription factor (COUP) and Ptx-1 were detected in the promoter. The importance of these putative control elements in ovary and brain-specific promoter has been assessed by sequence comparison among various species.