Elevated steroid sulfatase expression in breast cancers

Estrogen sulfotransferase and sulfatase in steroid homeostasis, metabolic disease, and cancer

Sulfation and desulfation of steroids are opposing processes that regulate the activation, metabolism, excretion, and storage of steroids, which account for steroid homeostasis. Steroid sulfation and desulfation are catalyzed by cytosolic sulfotransferase and steroid sulfatase, respectively. By modifying and regulating steroids, cytosolic sulfotransferase (SULT) and steroid sulfatase (STS) are also involved in the pathophysiology of steroid-related diseases, such as hormonal dysregulation, metabolic disease, and cancer. The estrogen sulfotransferase (EST, or SULT1E1) is a typical member of the steroid SULTs. This review is aimed to summarize the roles of SULT1E1 and STS in steroid homeostasis and steroid-related diseases.

Real-time visualization of sulfatase in living cells and in vivo with a ratiometric AIE fluorescent probe

Different from the traditional enzymatic hydrolysis strategy, we rationally developed a ratiometric fluorescence probe DQMT-OH with AIE characteristics for sulfatase detection utilizing the "Lock-Key" strategy. It can be successfully used to monitor sulfatase in living cells and in vivo through different fluorescent channels with good cell permeability and low cytotoxicity.

Aromatase and steroid sulfatase from human placenta

Cytochrome P450 aromatase (AROM) and steroid (estrone (E1)/dehydroepiandrosterone (DHEA)) sulfatase (STS) are the two key enzymes responsible for the biosynthesis of estrogens in human, and maintenance of the critical balance between androgens and estrogens. Human AROM, an integral membrane protein of the endoplasmic reticulum, is a member of the Fe-heme containing cytochrome P450 superfamily having a cysteine thiolate as the fifth Fe-coordinating ligand. It is the only enzyme known to catalyze the conversion of androgens with non-aromatic A-rings to estrogens characterized by the aromatic A-ring. Human STS, also an integral membrane protein of the endoplasmic reticulum, is a Ca2+-dependent enzyme that catalyzes the hydrolysis of sulfate esters of E1 and DHEA to yield the respective unconjugated steroids, the precursors of the most potent forms of estrogens and androgens, namely, 17β-estradiol (E2), 16α,17β-estriol (E3), testosterone (TST) and dihydrotestosterone (DHT). Expression of these steroidogenic enzymes locally within various organs and tissues of the endocrine, reproductive, and central nervous systems is the key for maintaining high levels of the reproductive steroids. Thus, the enzymes have been drug targets for the prevention and treatment of diseases associated with steroid hormone excesses, especially in breast and prostate malignancies and endometriosis. Both AROM and STS have been the subjects of vigorous research for the past six decades. In this article, we review the procedures of their extraction and purification from human term placenta are described in detail, along with the activity assays.

Structures and Functions of Human Placental Aromatase and Steroid Sulfatase, Two Key Enzymes in Estrogen Biosynthesis

Cytochrome P450 aromatase (AROM) and steroid sulfatase (STS) are the two key enzymes for the biosynthesis of estrogens in human, and maintenance of the critical balance between androgens and estrogens. Human AROM, an integral membrane protein of the endoplasmic reticulum, is a member of the cytochrome P450 superfamily. It is the only enzyme to catalyze the conversion of androgens with non-aromatic A-rings to estrogens characterized by the aromatic A-ring. Human STS, also an integral membrane protein of the endoplasmic reticulum, is a Ca²⁺-dependent enzyme that catalyzes the hydrolysis of sulfate esters of estrone and dehydroepiandrosterone to the unconjugated steroids, the precursors of the most potent forms of estrogens and androgens, namely, 17β-estradiol, 16α,17β-estriol, testosterone and dihydrotestosterone. Expression of these steroidogenic enzymes locally within organs and tissues of the endocrine, reproductive, and central nervous systems is the key for maintaining high levels of the reproductive steroids. The enzymes have been drug targets for the prevention and treatment of diseases associated with steroid hormone excesses, especially in breast, endometrial and prostate malignancies. Both enzymes have been the subjects of vigorous research for the past six decades. In this article, we review the important findings on their structure-function relationships, specifically, the work that began with unravelling of the closely guarded secrets, namely, the 3-D structures, active sites, mechanisms of action, origins of substrate specificity and the basis of membrane integration. Remarkably, these studies were conducted on the enzymes purified in their pristine forms from human placenta, the discarded and their most abundant source. The purification, assay, crystallization, and structure determination methodologies are described. Also reviewed are their functional quaternary organizations, post-translational modifications and the advancements made in the structure-guided inhibitor design efforts. Outstanding questions that still remain open are summarized in closing.

Activatable Near-Infrared Fluorescent and Photoacoustic Dual-Modal Probe for Highly Sensitive Imaging of Sulfatase In Vivo

Sulfatase is an important biomarker closely associated with various diseases. However, the state-of-the-art sulfatase probes are plagued with a short absorption/emission wavelength and limited sensitivity. Developing highly sensitive fluorescent probes for in vivo imaging of sulfatase remains a grand challenge. Herein, for the first time, an activatable near-infrared fluorescence/photoacoustic (NIRF/PA) dual-modal probe (Hcy-SA) for visualizing sulfatase activity in living cells and animals is developed. Hcy-SA is composed of a sulfate ester moiety as the recognition unit and a NIR fluorophore hemicyanine (Hcy-OH) as the NIRF/PA reporter. The designed probe exhibits a rapid response, excellent sensitivity, and high specificity for sulfatase detection in vitro. More importantly, cells and in vivo experiments confirm that Hcy-SA can be successfully applied for PA/NIRF dual-modal imaging of sulfatase activity in living sulfatase-overexpressed tumor cells and tumor-bearing animals. This probe can serve as a promising tool for sulfatase-related pathological research and cancer diagnosis.

Structure of human placental steroid sulfatase at 2.0 angstrom resolution: Catalysis, quaternary association, and a secondary ligand site

Human placental estrone (E1)/dehydroepiandrosterone (DHEA) sulfatase (human placental steroid sulfatase; hSTS) is an integral membrane protein of the endoplasmic reticulum. This Ca²⁺-dependent enzyme catalyzes the hydrolysis of sulfate esters of E1 and DHEA to yield the respective unconjugated steroids, which then act as precursors for the biosynthesis of 17β-estradiol (E2) and dihydrotestosterone (DHT), respectively, the most potent forms of estrogens and androgens. hSTS is a key enzyme for the local production of E2 and DHT in the breast and the prostate. The enzyme is known to be responsible for maintaining high levels of estrogens in the breast tumor cells. The crystal structure of hSTS purified from human placenta has previously been reported at 2.6 Å resolution. Here we present the structure of hSTS determined at the superior 2.0 Å resolution bringing new clarity to the atomic architecture of the active site. The molecular basis of catalysis and steroid-protein interaction are revisited in light of the new data. We also reexamine the enzyme's quaternary association and its implication on the membrane integration. A secondary ligand binding pocket at the intermolecular interface and adjacent to the active site access channel, buried into the gill of the mushroom-shaped molecule, has been identified. Its role as well as that of a phosphate ion bound to an exposed histidine side chain are examined from the structure-function perspective. Higher resolution data also aids in the tracing of an important loop missing in the previous structure.

The smoking estrogens - a potential synergy between estradiol and benzo(a)pyrene

According to recent statistics, Lung Cancer (LC) is one of the most frequently diagnosed tumor types, representing nearly 12% of all global cancer cases. Moreover, in recent years, an increased mortality rate and incidence of this cancer were observed, especially among nonsmokers. Lung cancer patients are often characterized by poor prognosis and low survival rates, which encourages the scientific community to investigate the biochemical and molecular processes leading to the development of this malignancy. Furthermore, the mechanisms of LC formation and progression are not yet fully elucidated due to their high complexity, as well as a multitude of environmental, genetic, and molecular factors involved. Even though LC's association with exposure to cigarette smoke is indisputable, current research provides evidence that the development of this cancer can also be affected by the presence of estrogens and their interaction with several tobacco smoke components. Hence, the main goal of this brief review was to investigate reports of a possible synergy between 17β estradiol (E2), the most biologically active estrogen, and benzo(a)pyrene (BaP), a strongly carcinogenic compound produced as a result of incomplete tobacco combustion. The literature sources demonstrate a possible carcinogenic synergy between estrogens, especially E2, and BaP, a toxic tobacco smoke component. Therefeore, the combined effect of disturbed estrogen production in cancer cells, as well as the molecular influence exerted by BaP, could explain the increased aggressiveness and rate of LC development. Summarizing, the synergistic effect of these risk factors is an interesting area of further research.

Steroid Sulphatase and Its Inhibitors: Past, Present, and Future

Steroid sulphatase (STS), involved in the hydrolysis of steroid sulphates, plays an important role in the formation of both active oestrogens and androgens. Since these steroids significantly impact the proliferation of both oestrogen- and androgen-dependent cancers, many research groups over the past 30 years have designed and developed STS inhibitors. One of the main contributors to this field has been Prof. Barry Potter, previously at the University of Bath and now at the University of Oxford. Upon Prof. Potter’s imminent retirement, this review takes a look back at the work on STS inhibitors and their contribution to our understanding of sulphate biology and as potential therapeutic agents in hormone-dependent disease. A number of potent STS inhibitors have now been developed, one of which, Irosustat (STX64, 667Coumate, BN83495), remains the only one to have completed phase I/II clinical trials against numerous indications (breast, prostate, endometrial). These studies have provided new insights into the origins of androgens and oestrogens in women and men. In addition to the therapeutic role of STS inhibition in breast and prostate cancer, there is now good evidence to suggest they may also provide benefits in patients with colorectal and ovarian cancer, and in treating endometriosis. To explore the potential of STS inhibitors further, a number of second- and third-generation inhibitors have been developed, together with single molecules that possess aromatase–STS inhibitory properties. The further development of potent STS inhibitors will allow their potential therapeutic value to be explored in a variety of hormone-dependent cancers and possibly other non-oncological conditions.

Gene expression profile of normal breast tissue and body mass index

BACKGROUND

In human breast, adipose tissue represents up to 80% of the total volume and plays a critical role in mammary gland remodeling. Given the emerging role of obesity in breast cancer growth and development, we explored the relationship between body mass index (BMI), as a proxy of woman's obesity status, and the expression in normal breast tissue from healthy women of a selected panel of genes, known to be involved in mammary gland homeostasis.

METHODS

Two independent publicly available datasets, composed of 180 specimens of normal breast tissue from reduction mammoplasty were interrogated. Differential gene expression among BMI classes was evaluated by ANOVA, and partial correlation coefficient was used to assay the correlation between genes controlling for BMI.

RESULTS

Despite the differences in microarray platforms and analytical procedures, the two datasets shared a core of 9 genes differentially expressed in BMI classes and significantly correlated with BMI. Four (44%) of these genes belong to the functional class of cytokines and cytokine receptors (IL1R1, IL2RA, IL12A, and IL12RB2). The others belong to the functional class of the epigenetic regulation (MEDAG and SETD7), signal transduction (STAT1), cell adhesion (ITGAV), and enzymatic activity (STS).

CONCLUSIONS

Although exploratory, present findings are in agreement with the role of inflammation modulators in the homeostasis of normal breast tissue and the believe that an increase in body adipose tissue may have a potentially dangerous local effect, through the increased expression of inflammation-related genes and the establishment of a low-grade chronic inflammation.

The Gut Microbiota Impact Cancer Etiology through "Phase IV Metabolism" of Xenobiotics and Endobiotics

The human gut microbiome intimately complements the human genome and gut microbial factors directly influence health and disease. Here we outline how the gut microbiota uniquely contributes to cancer etiology by processing products of human drug and endobiotic metabolism. We formally propose that the reactions performed by the gut microbiota should be classified as "Phase IV xenobiotic and endobiotic metabolism." Finally, we discuss new data on the control of cancer by the inhibition of gut microbial phase IV enzymes responsible for tumor initiation and progression.

Achieving the ratiometric imaging of steroid sulfatase in living cells and tissues with a two-photon fluorescent probe

Herein, a novel two-photon ratiometric fluorescence assay was proposed for monitoring endogenous steroid sulfatase (STS) activity, which could be applied for the ratiometric imaging of STS activity in the endoplasmic reticulum of living cells and tissues and also could be used to distinguish estrogen-dependent tumor cells from other types of cells.

Human steroid sulfatase induces Wnt/β-catenin signaling and epithelial-mesenchymal transition by upregulating Twist1 and HIF-1α in human prostate and cervical cancer cells

Steroid sulfatase (STS) catalyzes the hydrolysis of estrone sulfate and dehydroepiandrosterone sulfate (DHEAS) to their unconjugated biologically active forms. Although STS is considered a therapeutic target for estrogen-dependent diseases, the cellular functions of STS remain unclear. We found that STS induces Wnt/β-catenin s Delete ignaling in PC-3 and HeLa cells. STS increases levels of β-catenin, phospho-β-catenin, and phospho-GSK3β. Enhanced translocation of β-catenin to the nucleus by STS might activate transcription of target genes such as cyclin D1, c-myc, and MMP-7. STS knockdown by siRNA resulted in downregulation of Wnt/β-catenin signaling. β-Catenin/TCF-mediated transcription was also enhanced by STS. STS induced an epithelial-mesenchymal transition (EMT) as it reduced the levels of E-cadherin, whereas levels of mesenchymal markers such as N-cadherin and vimentin were enhanced. We found that STS induced Twist1 expression through HIFα activation as HIF-1α knockdown significantly blocks the ability of STS to induce Twist1 transcription. Furthermore, DHEA, but not DHEAS is capable of inducing Twist1. Treatment with a STS inhibitor prevented STS-mediated Wnt/β-catenin signaling and Twist1 expression. Interestingly, cancer cell migration, invasion, and MMPs expression induced by STS were also inhibited by a STS inhibitor. Taken together, these results suggest that STS induces Wnt/β-catenin signaling and EMT by upregulating Twist1 and HIF-1α. The ability of STS to induce the Wnt/β-catenin signaling and EMT has profound implications on estrogen-mediated carcinogenesis in human cancer cells.

Induction of Integrin Signaling by Steroid Sulfatase in Human Cervical Cancer Cells

Steroid sulfatase (STS) is an enzyme responsible for the hydrolysis of aryl and alkyl sulfates. STS plays a pivotal role in the regulation of estrogens and androgens that promote the growth of hormone-dependent tumors, such as those of breast or prostate cancer. However, the molecular function of STS in tumor growth is still not clear. To elucidate the role of STS in cancer cell proliferation, we investigated whether STS is able to regulate the integrin signaling pathway. We found that overexpression of STS in HeLa cells increases the protein and mRNA levels of integrin β1 and fibronectin, a ligand of integrin α5β1. Dehydroepiandrosterone (DHEA), one of the main metabolites of STS, also increases mRNA and protein expression of integrin β1 and fibronectin. Further, STS expression and DHEA treatment enhanced phosphorylation of focal adhesion kinase (FAK) at the Tyr 925 residue. Moreover, increased phosphorylation of ERK at Thr 202 and Tyr 204 residues by STS indicates that STS activates the MAPK/ERK pathway. In conclusion, these results suggest that STS expression and DHEA treatment may enhance MAPK/ERK signaling through up-regulation of integrin β1 and activation of FAK.

mRNA expression of steroidogenic enzymes, steroid hormone receptors and their coregulators in gastric cancer

Epidemiological and experimental findings suggest that the development of gastric cancer (GC) is regulated by steroid hormones. In postmenopausal women and older men, the majority of steroid hormones are produced locally in peripheral tissue through the enzymatic conversion of steroid precursors. Therefore, using reverse transcription-quantitative polymerase chain reaction analysis, the mRNA expression of genes encoding steroidogenic enzymes, including steroid sulfatase (STS), hydroxy-delta-5-steroid dehydrogenase 3 beta- and steroid delta-isomerase 1 (HSD3B1), 17β-hydroxysteroid dehydrogenase type 7 and aromatase (CYP19A1), was investigated in primary tumoral and adjacent healthy gastric mucosa from 60 patients with GC. Furthermore, the mRNA levels for estrogen receptor α, estrogen receptor β (ESR2) and androgen receptor (AR), along with their coregulators, including proline, glutamate and leucine rich protein 1, CREB binding protein, nuclear receptor coactivator 1 (NCOA1), nuclear receptor corepressor 1 (NCOR1) and nuclear receptor subfamily 2 group F member 1 (NR2F1), were investigated. Additionally, the association between the mRNA expression of these genes and the clinicopathological features of patients with GC was examined. Significantly decreased levels of STS, HSD3B1, ESR2, AR, NCOA1 and NCOR1 mRNA, in addition to significantly increased levels of CYP19A1 mRNA were demonstrated in tumoral tissue samples compared with adjacent healthy gastric tissue samples. Deregulated expression of these genes in the analyzed tissue samples was associated with certain clinicopathological features of GC, such as age and localization of the tumor. The results of the current study suggest that all of the genes analyzed are expressed in tumoral and adjacent healthy gastric mucosa. In addition, the results indicate that abnormal expression of STS, ESR2, AR, NCOA1 and NCOR1 may serve a role in the development and progression of GC, and may be associated with specific clinicopathological features in patients with GC.

Exploring estrogenic activity in lung cancer

It is well known that a connection between xenobiotics inhalation, especially tobacco combustion and Lung Cancer development is strongly significant and indisputable. However, recent studies provide evidence indicating that another factors such as, estrogens are also involved in lung carcinoma biology and metabolism. Although the status of estrogen receptors (ER), in both cancerous and healthy lung tissue has been well documented, there is still inconclusive data with respect of which isoform of the receptor is present in the lungs. However according to several studies, ERβ appears to be predominant form. Apart from ERs, estrogens can work through a recently discovered G-coupled estrogen receptor. Binding with both types of the receptors causes a signal, which leads to i.e. enhanced cell proliferation. There are many published reports which suggest that estrogen can be synthesized in situ in lung cancer. Some disturbances in the activity and expression levels of enzymes involved in estrogen synthesis were proved. This suggests that increased amounts of sex-steroid hormones can affect cells biology and be the reason of the accelerated development and pathogenesis of lung cancer. There also exist phenomena which associate estrogenic metabolism and tobacco combustion and its carcinogenic influence on the lungs. Compounds present in cigarette smoke induce the activity of CYP1B1, the enzyme responsible for estrogenic metabolism and synthesis of their cateholic derivatives. These structures during their redox cycle are able to release reactive oxygen species or form DNA adduct, which generally leads to destruction of genetic material. This process may explain the synergistic effect of smoking and estrogens on estrogen-dependent lung cancer development.

In touch with your feminine side: how oestrogen metabolism impacts prostate cancer

Prostate cancer is the primary cancer in males, with increasing global incidence rates making this malignancy a significant healthcare burden. Androgens not only promote normal prostate maturity but also influence the development and progression of prostate cancer. Intriguingly, evidence now suggests endogenous and exogenous oestrogens, in the form of phytoestrogens, may be equally as relevant as androgens in prostate cancer growth. The prostate gland has the molecular mechanisms, catalysed by steroid sulphatase (STS), to unconjugate and utilise circulating oestrogens. Furthermore, prostate tissue also expresses enzymes essential for local oestrogen metabolism, including aromatase (CYP19A1) and 3β- and 17β-hydroxysteroid dehydrogenases. Increased expression of these enzymes in malignant prostate tissue compared with normal prostate indicates that oestrogen synthesis is favoured in malignancy and thus may influence tumour progression. In contrast to previous reviews, here we comprehensively explore the epidemiological and scientific evidence on how oestrogens impact prostate cancer, particularly focusing on pre-receptor oestrogen metabolism and subsequent molecular action. We analyse how molecular mechanisms and metabolic pathways involved in androgen and oestrogen synthesis intertwine to alter prostate tissue. Furthermore, we speculate on whether oestrogen receptor status in the prostate affects progression of this malignancy.

Sulfatase inhibitors for recidivist breast cancer treatment: A chemical review

Steroid sulfatase (STS) plays a momentous role in the conversion of sulfated steroids, which are biologically inactive, into biologically active un-sulfated steroid hormones, which support the development and growth of a number of hormone-dependent cancers, including breast cancer. Therefore, inhibitors of STS are supposed to be potential drugs for the treatment of breast and other steroid-dependent cancers. The present review concentrates on broad chemical classification of steroid sulfatase inhibitors. The inhibitors reviewed are classified into four main categories: Steroid sulfamate based inhibitors; Steroid non-sulfamate based inhibitors; Non-steroidal sulfamate based inhibitors; Non-steroidal non-sulfamate based inhibitors. A succinct overview of current treatment of cancer, estradiol precursors, STS enzyme and its role in breast cancer is herein described.

Discovery and Development of the Aryl O-Sulfamate Pharmacophore for Oncology and Women's Health

In 1994, following work from this laboratory, it was reported that estrone-3-O-sulfamate irreversibly inhibits a new potential hormone-dependent cancer target steroid sulfatase (STS). Subsequent drug discovery projects were initiated to develop the core aryl O-sulfamate pharmacophore that, over some 20 years, have led to steroidal and nonsteroidal drugs in numerous preclinical and clinical trials, with promising results in oncology and women's health, including endometriosis. Drugs have been designed to inhibit STS, e.g., Irosustat, as innovative dual-targeting aromatase-steroid sulfatase inhibitors (DASIs) and as multitargeting agents for hormone-independent tumors, such as the steroidal STX140 and nonsteroidal counterparts, acting inter alia through microtubule disruption. The aryl sulfamate pharmacophore is highly versatile, operating via three distinct mechanisms of action, and imbues attractive pharmaceutical properties. This Perspective gives a personal view of the work leading both to the therapeutic concepts and these drugs, their current status, and how they might develop in the future.

The Regulation of Steroid Action by Sulfation and Desulfation

Steroid sulfation and desulfation are fundamental pathways vital for a functional vertebrate endocrine system. After biosynthesis, hydrophobic steroids are sulfated to expedite circulatory transit. Target cells express transmembrane organic anion-transporting polypeptides that facilitate cellular uptake of sulfated steroids. Once intracellular, sulfatases hydrolyze these steroid sulfate esters to their unconjugated, and usually active, forms. Because most steroids can be sulfated, including cholesterol, pregnenolone, dehydroepiandrosterone, and estrone, understanding the function, tissue distribution, and regulation of sulfation and desulfation processes provides significant insights into normal endocrine function. Not surprisingly, dysregulation of these pathways is associated with numerous pathologies, including steroid-dependent cancers, polycystic ovary syndrome, and X-linked ichthyosis. Here we provide a comprehensive examination of our current knowledge of endocrine-related sulfation and desulfation pathways. We describe the interplay between sulfatases and sulfotransferases, showing how their expression and regulation influences steroid action. Furthermore, we address the role that organic anion-transporting polypeptides play in regulating intracellular steroid concentrations and how their expression patterns influence many pathologies, especially cancer. Finally, the recent advances in pharmacologically targeting steroidogenic pathways will be examined.

Dual effect of metformin on growth inhibition and oestradiol production in breast cancer cells

Evidence has been accumulating for a role for metformin in reducing breast cancer risk in post-menopausal women. It inhibits growth of breast cancer cells via several mechanisms, primarily the AMPK/mTOR signalling pathway. Another possible protective mechanism may be the ability of metformin to inhibit aromatase activity. In the present study, we investigated the effects of metformin on the basal growth of MCF-7 cells, after oestradiol (E2) stimulation and after the inhibition of mTOR by rapamycin. Secondly, we investigated the effects of metformin on the activity of a number of steroidogenic enzymes and the mRNA expression of aromatase and steroid sulphatase (STS). High doses of metformin significantly inhibited both basal and oestrogen-stimulated cell division. Low-dose rapamycin (10-10 M) did not inhibit growth, but the addition of metformin induced a significant reduction in growth. High-dose rapamycin (10-8 M) inhibited growth, and this was further attenuated by the addition of metformin. Exposure to low (10-7 M) and high (10-4 M) doses of metformin for 7-10 days significantly reduced the conversion of androstenedione (ANDRO) and testosterone (TESTO) (both requiring aromatase), but not the conversion of oestrone or oestrone sulphate (ES) via 17β-hydroxysteroid dehydrogenase/sulphatase to E2. This attenuation was via a downregulation in the expression of total aromatase mRNA and promoter II, whilst the expression of sulphatase was unaffected by metformin. In conclusion, plasma levels of metformin have a dual therapeutic action, first by directly inhibiting cell proliferation which can be augmented by rapamycin analogues, and secondly, by inhibiting aromatase activity and reducing the local conversion of androgens to E2.

Estrogen biosynthesis and action in ovarian cancer

Ovarian cancer is still the deadliest of all gynecologic malignancies in women worldwide. This is attributed to two main features of these tumors, namely, (i) a diagnosis at an advanced tumor stage, and, (ii) the rapid onset of resistance to standard chemotherapy after an initial successful therapy with platin- and taxol-derivatives. Therefore, novel targets for an early diagnosis and better treatment options for these tumors are urgently needed. Epidemiological data show that induction and biology of ovarian cancer is related to life-time estrogen exposure. Also experimental data reveal that ovarian cancer cells share a number of estrogen regulated pathways with other hormone-dependent cancers, e.g., breast and endometrial cancer. However, ovarian cancer is a heterogeneous disease and the subtypes are quite different with respect to mutations, origins, behaviors, markers, and prognosis and respond differently to standard chemotherapy. Therefore, a characterization of ovarian cancer subtypes may lead to better treatment options for the various subtypes and in particular for the most frequently observed high-grade serous ovarian carcinoma. For this intention, further studies on estrogen-related pathways and estrogen formation in ovarian cancer cells are warranted. The review gives an overview on ovarian cancer subtypes and explains the role of estrogen in ovarian cancer. Furthermore, enzymes active to synthesize and metabolize estrogens are described and strategies to target these pathways are discussed.

Breast cancer: current and future endocrine therapies

Endocrine therapy forms a central modality in the treatment of estrogen receptor positive breast cancer. The routine use of 5 years of adjuvant tamoxifen has improved survival rates for early breast cancer, and more recently has evolved in the postmenopausal setting to include aromatase inhibitors. The optimal duration of adjuvant endocrine therapy remains an active area of clinical study with recent data supporting 10 years rather than 5 years of adjuvant tamoxifen. However, endocrine therapy is limited by the development of resistance, this can occur by a number of possible mechanisms and numerous studies have been performed which combine endocrine therapy with agents that modulate these mechanisms with the aim of preventing or delaying the emergence of resistance. Recent trial data regarding the combination of the mammalian target of rapamycin (mTOR) inhibitor, everolimus with endocrine therapy have resulted in a redefinition of the clinical treatment pathway in the metastatic setting. This review details the current endocrine therapy utilized in both early and advanced disease, as well as exploring potential new targets which modulate pathways of resistance, as well as agents which aim to modulate adrenal derived steroidogenic hormones.

Induction of steroid sulfatase expression in PC-3 human prostate cancer cells by insulin-like growth factor II

Human steroid sulfatase (STS) plays an important role in regulating the formation of biologically active estrogens and may be a promising target for treating estrogen-mediated carcinogenesis. The molecular mechanism of STS gene expression, however, is still not clear. Growth factors are known to increase STS activity but the changes in STS expression have not been completely understood. To determine whether insulin-like growth factor (IGF)-II can induce STS gene expression, the effects of IGF-II on STS expression were studied in PC-3 human prostate cancer cells. RT-PCR and Western blot analysis showed that IGF-II treatment significantly increased the expression of STS mRNA and protein in concentration- and time-dependent manners. To understand the signaling pathway by which IGF-II induces STS gene expression, the effects of specific PI3-kinase/Akt and NF-κB inhibitors were determined. When the cells were treated with IGF-II and PI3-kinase/Akt inhibitors, such as LY294002, wortmannin, or Akt inhibitor IV, STS expression induced by IGF-II was significantly blocked. Moreover, we found that NF-κB inhibitors, such as MG-132, bortezomib, Bay 11-7082 or Nemo binding domain (NBD) binding peptide, also strongly prevented IGF-II from inducing STS gene expression. We assessed whether IGF-II activates STS promoter activity using transient transfection with a luciferase reporter. IGF-II significantly stimulated STS reporter activity. Furthermore, IGF-II induced expression of 17β-hydroxysteroid dehydrogenase (HSD) 1 and 3, whereas it reduced estrone sulfotransferase (EST) gene expression, causing enhanced estrone and β-estradiol production. Taken together, these results strongly suggest that IGF-II induces STS expression via a PI3-kinase/Akt-NF-κB signaling pathway in PC-3 cells and may induce estrogen production and estrogen-mediated carcinogenesis.

Bacterial Lipopolysaccharides Induce Steroid Sulfatase Expression and Cell Migration through IL-6 Pathway in Human Prostate Cancer Cells

Steroid sulfatase (STS) is responsiblefor the conversion of estrone sulfate to estrone that can stimulate growth in endocrine-dependent tumors such as prostate cancer. Although STS is considered as a therapeutic target for the estrogen-dependent diseases, cellular function of STS are still not clear. Previously, we found that tumor necrosis factor (TNF)-α significantly enhances steroid sulfatase expression in PC-3 human prostate cancer cells through PI3K/Akt-dependent pathways. Here, we studied whether bacterial lipopolysaccharides (LPS) which are known to induce TNF-α may increase STS expression. Treatment with LPS in PC-3 cells induced STS mRNA and protein in concentration- and time-dependent manners. Using luciferase reporter assay, we found that LPS enhanced STS promoter activity. Moreover, STS expression induced by LPS increased PC-3 tumor cell migration determined by wound healing assay. We investigated that LPS induced IL-6 expression and IL-6 increased STS expression. Taken together, these data strongly suggest that LPS induces STS expression through IL-6 pathway in human prostate cancer cells.

Steroid derivatives as inhibitors of steroid sulfatase

Sulfated steroids function as a storage reservoir of biologically active steroid hormones. The sulfated steroids themselves are biologically inactive and only become active in vivo when they are converted into their desulfated (unconjugated) form by the enzyme steroid sulfatase (STS). Inhibitors of STS are considered to be potential therapeutics for the treatment of steroid-dependent cancers such as breast, prostate and endometrial cancer. The present review summarizes steroid derivatives as inhibitors of STS covering the literature from the early years of STS inhibitor development to October of 2012. A brief discussion of the function, structure and mechanism of STS and its role in estrogen receptor-positive (ER+) hormone-dependent breast cancer is also presented. This article is part of a Special Issue entitled "Synthesis and biological testing of steroid derivatives as inhibitors".

Current status on development of steroids as anticancer agents

Steroids are important biodynamic agents. Their affinities for various nuclear receptors have been an interesting feature to utilize them for drug development particularly for receptor mediated diseases. Steroid biochemistry and its crucial role in human physiology, has attained importance among the researchers. Recent years have seen an extensive focus on modification of steroids. The rational modifications of perhydrocyclopentanophenanthrene nucleus of steroids have yielded several important anticancer lead molecules. Exemestane, SR16157, fulvestrant and 2-methoxyestradiol are some of the successful leads emerged on steroidal pharmacophores. The present review is an update on some of the steroidal leads obtained during past 25 years. Various steroid based enzyme inhibitors, antiestrogens, cytotoxic conjugates and steroidal cytotoxic molecules of natural as well as synthetic origin have been highlighted. This article is part of a Special Issue entitled "Synthesis and biological testing of steroid derivatives as inhibitors".

Estrone-3-sulphate, a potential novel ligand for targeting breast cancers

The current study investigates the potential of estrone-3-sulphate (E3S) as a ligand for targeting Organic Anion Transporting Polypeptides (OATP), a family of membrane associated uptake transporters, for detection and diagnosis of hormone dependent breast cancers. E3S, an OATP substrate, is a predominant source of tumour estradiol in post-menopausal patients. To assess the potential of E3S as a ligand, distribution of exogenous E3S was determined at the whole body, tumour and cellular levels in murine models of hormone-dependent (MCF-7) and independent (MDA-MB-231) breast cancers. The highest levels of tumour uptake were observed at 6 h post injection (p.i) with significant difference (p = 0.04) between the level in MCF-7 (13.9±3.1%ID/g) and MDA-MB-231 (10.4±1.1%ID/g) (%ID/g: percentage of the total injected dose per gram tissue). The highest tumour-to-blood ratios (MCF-7∶7.4±1.2; MDA-MB-231∶9.1±2.1) were observed at 48 p.i., and highest tumour-to-muscle ratios (MCF-7∶10.7±1.5; MDA-MB-231∶3.8±0.7) were observed at 6 h p.i. Analogous to total tumour uptake, ex vivo tumour cell uptake at 2 h p.i. was 6 fold higher in MCF-7 in comparison to MDA-MB-231 tumour cells. Blocking studies, conducted by pre-administration of 100-fold excess E3S, resulted in significantly lower (MCF-7: p = 0.01; MDA-MB-231: p = 0.02) tumour uptake in both xenograft models, suggesting the involvement of an active carrier-mediated process. The expression of OATP1A2 was detected in tumour sections from both xenografts, with significantly higher expression (p = 0.002) in the MCF-7 xenografts. Overall, the higher tumour uptake and tumour-to-muscle ratio, alongside the higher expression of OATP1A2, in the MCF-7 xenograft model suggests the potential of E3S to serve as a novel ligand for targeting hormone dependent breast cancers.

Studying plant-derived coumarins for their pharmacological and therapeutic properties as potential anticancer drugs

Coumarins have attracted intense interest in recent years because of their diverse pharmacological properties. Among these properties, their anticancer effect was most extensively examined. In this review, their broad range of effects on the tumours as shown by various in vitro and in vivo experiments as well as clinical investigations is discussed. Studies have indicated that coumarins elicit inhibitory effects on cell growth of various carcinoma cell lines and may be potential candidates for cancer therapy. These natural compounds have served as valuable leads for further design and synthesis of more active analogues. In view of the relative simplicity of the coumarin compounds and their mechanism of action, the coumarin pharmacophore may serve as an important model on which to develop new patterns in cancer chemotherapy. The aim of this review is to examine in detail the properties of the title compounds as anticancer agents. In view of their comparatively low toxicity, relative cheapness, presence in the diet and occurrence in various herbal remedies, it appears important to evaluate their anticancer potentialities. Moreover their synergistic activity in combination therapy with other well-known anticancer drugs could be the basis for the development of rational approaches to new forms of cancer chemotherapy.

Origins and actions of tumor necrosis factor α in postmenopausal breast cancer

Tumor necrosis factor α (TNFα) has many roles in both physiological and pathological states. Initially thought to cause necrosis of tumors, research has shown that in many tumor types, including breast cancer, TNFα contributes to growth and proliferation. The presence of TNFα-derived from the tumor and infiltrating immune cells-within a breast tumor microenvironment has been correlated with a more aggressive phenotype, and the postmenopausal ER+ subtype of breast cancers appears to strongly respond to its many pro-growth signaling functions. We discuss how TNFα regulates estrogen biosynthesis within the breast, affecting the activity of the key estrogen-synthesizing enzymes aromatase, estrone sulfatase, and 17β-HSD type 1. Additionally, we describe the anti-adipogenic actions of TNFα that are critical in preventing adjacent estrogen-producing adipose fibroblasts from differentiating, ensuring that the tumor maintains a constant source of estrogen-producing cells. We examine how the increased risk of developing breast cancer in older and obese individuals may be linked to the levels of TNFα in the body. Finally, we evaluate the feasibility of targeting TNFα and its associated pathways as a novel approach to breast cancer therapeutics.

Differential role of organic anion-transporting polypeptides in estrone-3-sulphate uptake by breast epithelial cells and breast cancer cells

The purpose of this study was to investigate the differential expression and function of organic anion-transporting polypeptides (OATPs) in breast epithelial and breast cancer cells. Estrone-3-sulfate (E3S), a substrate for 7 of 11 OATPs, is a predominant source of tumor estrogen in postmenopausal, hormone-dependent patients with breast cancer. Overexpression of certain OATPs (e.g., OATP1A2) reported in breast tumor tissues compared with surrounding normal tissues could contribute toward two to three times higher tumoral E3S concentration. Little is known about expression and function of other OATP family members among breast epithelial and breast cancer cells. We therefore compared gene and protein expression of seven OATPs (OATP1A2, OATP1B1, OATP1B3, OATP1C1, OATP2B1, OATP3A1, and OATP4A1) in immortalized breast epithelial cells (MCF10A), hormone-dependent breast cancer cells (MCF7), and hormone-independent breast cancer cells (MDA/LCC6-435, MDA-MB-231, and MDA-MB-468) by quantitative polymerase chain reaction and immunoblotting, respectively. Expression of solute carrier superfamily encoding for OATPs (SLCO) 1A2, 1B1, 1B3, 2B1, and 3A1 is exclusive, similar, or significantly higher in cancer cells compared with MCF10A cells. Protein expression of OATPs is found to be either exclusive or higher in cancer cells compared with MCF10A cells. Specificity of OATP-mediated E3S uptake is observed only in cancer cells, with the highest total uptake in MCF7 cells. Transport kinetics of E3S uptake demonstrates transport efficiency that is 10 times greater in the MCF7 cells than in the hormone-independent cells. These data suggest that OATPs could be a novel therapeutic target for hormone-dependent breast cancers, particularly in postmenopausal patients, where the major source of tumor estrogen is E3S.

Induction of steroid sulfatase expression by tumor necrosis factor-α through phosphatidylinositol 3-kinase/Akt signaling pathway in PC-3 human prostate cancer cells

Steroid sulfatase (STS) is responsible for the hydrolysis of aryl and alkyl steroid sulfates and has a pivotal role in regulating the formation of biologically active estrogens. STS may be considered a new promising drug target for treating estrogen-mediated carcinogenesis. However, the molecular mechanism of STS expression is not well-known. To investigate whether tumor necrosis factor (TNF)-α is able to regulate gene transcription of STS, we studied the effect of TNF-α on STS expression in PC-3 human prostate cancer cells. RT-PCR and Western blot analysis showed that TNF-α significantly induced the expression of STS mRNA and protein in a concentration- and time-dependent manner. Treatment with TNF-α resulted in a strong increase in the phosphorylation of Akt on Ser-473 and when cells were treated with phosphatidylinositol (PI) 3-kinase inhibitors such as LY294002 or wortmannin, or Akt inhibitor (Akt inhibitor IV), induction of STS mRNA expression by TNF-α was significantly prevented. Moreover, activation of Akt1 by expressing the constitutively active form of Akt1 increased STS expression whereas dominant-negative Akt suppressed TNF-α-mediated STS induction. We also found that TNF-α is able to increase STS mRNA expression in other human cancer cells such as LNCaP, MDA-MB-231, and MCF-7 as well as PC-3 cells. Taken together, our results strongly suggest that PI 3-kinase/Akt activation mediates induction of human STS gene expression by TNF-α in human cancer cells.

Steroid sulfatase inhibitors for estrogen- and androgen-dependent cancers

Estrogens and androgens are instrumental in the maturation of many hormone-dependent cancers. Consequently, the enzymes involved in their synthesis are cancer therapy targets. One such enzyme, steroid sulfatase (STS), hydrolyses estrone sulfate, and dehydroepiandrosterone sulfate to estrone and dehydroepiandrosterone respectively. These are the precursors to the formation of biologically active estradiol and androstenediol. This review focuses on three aspects of STS inhibitors: 1) chemical development, 2) biological activity, and 3) clinical trials. The aim is to discuss the importance of estrogens and androgens in many cancers, the developmental history of STS inhibitor synthesis, the potency of these compounds in vitro and in vivo and where we currently stand in regards to clinical trials for these drugs. STS inhibitors are likely to play an important future role in the treatment of hormone-dependent cancers. Novel in vivo models have been developed that allow pre-clinical testing of inhibitors and the identification of lead clinical candidates. Phase I/II clinical trials in postmenopausal women with breast cancer have been completed and other trials in patients with hormone-dependent prostate and endometrial cancer are currently active. Potent STS inhibitors should become therapeutically valuable in hormone-dependent cancers and other non-oncological conditions.

Irosustat: a first-generation steroid sulfatase inhibitor in breast cancer

Endocrine therapy is a key modality in the management of breast cancer, with current options for postmenopausal women including tamoxifen, aromatase inhibitors and fulvestrant. Unfortunately, in spite of these advances, many women still relapse or progress on endocrine therapy. Given that resistance (de novo or acquired resistance) is a major limiting factor in the use of endocrine therapy, additional endocrine therapies with novel methods of action are required. Steroid sulfatase, which is responsible for the conversion of estrone sulfate to estrone, as well as dehydroepiandrosterone sulfate to dehydroepiandrosterone, has been implicated in endocrine resistance. In this article, we summarize the preclinical and clinical data to support the potential role of steroid sulfatase in breast cancer, as well as the current data on the first available steroid sulfatase inhibitor named irosustat (STX64; 667 Coumate; BN83495), and discuss its potential clinical development.

Steroid sulfatase: a pivotal player in estrogen synthesis and metabolism

Steroid sulfatase plays a pivotal role in regulating the formation of biologically active steroids from inactive steroid sulfates. It is responsible for the hydrolysis of estrone sulfate and dehydroepiandrosterone sulfate to estrone and dehydroepiandrosterone, respectively, both of which can be subsequently reduced to steroids with estrogenic properties (i.e. estradiol and androstenediol) that can stimulate the growth of tumors in hormone-responsive tissues of the breast, endometrium and prostate. Hence, the action of steroid sulfatase is implicated in physiological processes and pathological conditions. It has been five years since our group last reviewed the important role of this enzyme in steroid synthesis and the progress made in the development of potent inhibitors of this important enzyme target. This timely review therefore concentrates on recent advances in steroid sulfatase research, and summarises the findings of clinical trials with Irosustat (BN83495), the only steroid sulfatase inhibitor that is being trialed in postmenopausal women with breast or endometrial cancer.

Uptake transporter organic anion transporting polypeptide 1B3 contributes to the growth of estrogen-dependent breast cancer

Estrone-3-sulfate is one of the most abundant estrogen precursors in postmenopausal women. We previously showed that estrone-3-sulfate transporters are present in human breast cancer-derived MCF-7 cells (J. Pharmacol. Exp. Ther. 311 (2004) 1032-1037) and that inhibition of estrone-3-sulfate uptake resulted in the suppression of cell growth (Pharm. Res. 22 (2005) 1634-1641); therefore, estrone-3-sulfate transporter should be a novel target for therapy of hormone-dependent breast cancers. The purpose of the present study is to identify the transporter(s) responsible for the uptake of estrone-3-sulfate in breast cancer cells. We obtained two subclones of MCF-7 cells with different estrone-3-sulfate uptake activities and searched for differentially expressed transporter genes by means of DNA microarray analysis. Among several candidate transporters identified, OATP1B3 was further evaluated, since the uptake characteristics of estrone-3-sulfate by MCF-7 cells seemed consistent with the transport properties of OATP1B3. The contribution of OATP1B3 to estrone-3-sulfate uptake by MCF-7 cells was examined by the relative activity factor (RAF) method, and was calculated to amount to 6%. This result suggests that OATP1B3 is one of the transporters contributing to the supply of the estrogen precursor estrone-3-sulfate to estrogen-dependent breast cancer cells.

Expression of sulfotransferases and sulfatases in human breast cancer: impact on resveratrol metabolism

Resveratrol is a naturally occurring anticancer compound present in grapes and wine that undergoes pronounced metabolism in human intestine and liver. In order to determine whether resveratrol is also bio-transformed in human breast carcinoma, metabolism experiments were conducted in breast tumor and adjacent non-tumorous specimens from 13 patients. Resveratrol was metabolized in cytosolic tissue fractions to resveratrol-3-O-sulfate: the formation rates were up to 33.5-fold higher in cancer samples than in peritumoral tissue. Further quantitative real-time RT-PCR analysis revealed similar expression of sulfotransferases SULT1A2, 1A3, and 1E1 in the paired control and tumor tissues. Sulfotransferase SULT1A1 expression was below the detection limit in all samples. Interestingly, mRNA expression of steroid sulfatase STS, but not of arylsulfatases ARS-A and ARS-B, was significantly higher (p<0.0017) in non-malignant specimens than in tumor tissue samples, which might explain the higher resveratrol-3-O-sulfate concentrations in breast cancer specimens. Cellular localization of SULT1A3 and STS was also assessed by indirect immunofluorescence on paraffin-embedded sections from control and malignant breast tissue clearly showing a correlation of qRT-PCR data with protein expression of these two enzymes. Our data elucidate the metabolism of resveratrol in malignant and non-malignant breast tissue, which must be considered in humans after oral uptake of dietary resveratrol as a chemopreventive agent.

Shikonin, an ingredient of Lithospermum erythrorhizon, down-regulates the expression of steroid sulfatase genes in breast cancer cells

Steroid sulfatase (STS) has an important role in regulating the biosynthesis of estrogen within breast tumors. We aimed to investigate whether shikonin, an ingredient of Lithospermum erythrorhizon, could modulate STS expression in breast cancer cells. By MTT assay, shikonin inhibited the cell proliferation of breast cancer cells MCF-7 and SK-BR-3. Moreover, by semi-quantitative/quantitative reverse transcription polymerase chain reaction and dual-luciferase reporter based bioluminescent measurements, the mRNA and enzymatic activity levels of STS were decreased after shikonin treatment. Concluding, shikonin could act as a selective estrogen enzyme modulator by down-regulating the STS expression.

Transcriptional control of human steroid sulfatase

Steroid sulfatase (STS) is a membrane-bound microsomal enzyme that hydrolyzes various alkyl and aryl steroid sulfates, leading to the in situ formation of biologically active hormones. The entire human STS gene spans over approximately 200kbp of which the first 100kbp include the regulatory region, while the STS-coding region is located downstream. Previous studies indicated that STS expression, in different human tissues, could be regulated by at least six different promoters associated with alternative first exons. Here, we describe two new splicing patterns: the first, found in the prostatic cell line PC3, is based upon a partially coding new first exon (0d) that is spliced to a new second exon (1e). The second variant was found in the ovary and it is characterized by the novel splicing of the untranslated exon 0b to exon 0c, which is then spliced to the common exon 1b. We also report the results of a multiplex ligation-dependent probe amplification (RT-MLPA) analysis for the simultaneous detection, in qualitative and/or semi-quantitative terms, of the transcription patterns of STS in different tissues.

The development of steroid sulfatase inhibitors for hormone-dependent cancer therapy

Steroid sulfatase (STS) regulates the hydrolysis of steroid sulfates to their unconjugated forms. Estrone sulfate and dehydroepiandrosterone sulfate can be hydrolyzed by STS to estrone and dehydroepiandrosterone, respectively, with these steroids being the precursors for the synthesis of more biologically active estrogens or androgens. A number of potent STS inhibitors have now been developed including STX64, which entered a phase I trial for the treatment of postmenopausal women with advanced metastatic hormone-dependent breast cancer. The results from this phase I trial were encouraging, suggesting that STS inhibitors may also have a role in the treatment of other hormone-dependent cancers including those of the endometrium, ovary, and prostate. In this paper the potential use of STS inhibitors to treat these hormone-dependent cancers is reviewed. In addition, results from in vitro studies show that Ishikawa endometrial cancer cells, OVCAR-3 ovarian cancer cells, and LNCaP prostate cancer cells all possess significant STS activity. Furthermore, STS activity in these cells can be almost completely inhibited by STX64 or the second-generation STS inhibitor, STX213. Results from these investigations therefore suggest that STS inhibitors could have therapeutic potential for the treatment of a range of hormone-dependent cancers.