Inhibition of steryl sulfatase activity in LNCaP human prostate cancer cells

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.

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.

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.

Testicular steroid sulfatase overexpression is associated with Leydig cell dysfunction in primary spermatogenic failure

BACKGROUND

Decreased testosterone (T) to LH ratio and increased 17β-estradiol (E2) serum concentrations represent a common finding among patients with severe spermatogenic failure, suggesting a concurrent Leydig cell steroidogenic dysfunction. Aromatase overexpression has been associated with increased serum and intratesticular E2 in these patients. However, it is unknown whether the sulfatase pathway contributes to the increased availability of active estrogens in patients with primary spermatogenic failure.

OBJECTIVES

To assess estrogen sulfotransferase (SULT1E1) and steroid sulfatase (STS) mRNA abundance in testicular tissue of patients with Sertoli cell-only syndrome (SCOS) and normal tissues, its association with serum and intratesticular hormone levels, and to explore the mRNA and protein testicular localization of both enzymes.

MATERIALS AND METHODS

Testicular tissues of 23 subjects with SCOS (cases) and 22 patients with obstructive azoospermia and normal spermatogenesis (controls) were obtained after biopsy. SULT1E1 and STS transcripts accumulation was quantified by RT-qPCR. For mRNA and protein localization, we performed RT-qPCR in Leydig cell clusters and seminiferous tubules isolated by laser-capture microdissection and immunofluorescence in testicular tissues. Serum and intratesticular hormones were measured by immunoradiometric assays.

RESULTS

SULT1E1 mRNA accumulation was similar in both groups. The amount of STS mRNA was higher in cases (p = 0.007) and inversely correlated with T/LH ratio (r = -0.402; p = 0.02). Also, a near significant correlation was observed with intratesticular E2 (r = 0.329, p = 0.057), in agreement with higher intratesticular E2 in cases (p < 0.001). Strong STS immunoreaction was localized in the wall of small blood vessels but not in Leydig cells. Both SULT1E1 and STS mRNA abundance was similar in Leydig cell clusters and the tubular compartment, except for lower SUTL1E1 mRNA in the seminiferous tubules of SCOS patients (p = 0.001).

CONCLUSIONS

Our results suggest that an unbalance of the STS/SULT1E1 pathway contributes to the testicular hyperestrogenic microenvironment in patients with primary spermatogenic failure and Leydig cell dysfunction.

The role of adrenal derived androgens in castration resistant prostate cancer

Castration resistant prostate cancer (CRPC) remains androgen dependant despite castrate levels of circulating testosterone following androgen deprivation therapy, the first line of treatment for advanced metstatic prostate cancer. CRPC is characterized by alterations in the expression levels of steroidgenic enzymes that enable the tumour to derive potent androgens from circulating adrenal androgen precursors. Intratumoral androgen biosynthesis leads to the localized production of both canonical androgens such as 5α-dihydrotestosterone (DHT) as well as less well characterized 11-oxygenated androgens, which until recently have been overlooked in the context of CRPC. In this review we discuss the contribution of both canonical and 11-oxygenated androgen precursors to the intratumoral androgen pool in CRPC. We present evidence that CRPC remains androgen dependent and discuss the alterations in steroidogenic enzyme expression and how these affect the various pathways to intratumoral androgen biosynthesis. Finally we summarize the current treatment strategies for targeting adrenal derived androgen biosynthesis.

Intracrinology-revisited and prostate cancer

The formation of steroid hormones in peripheral target tissues is referred to as their intracrine formation. This process occurs in hormone dependent malignancies such as prostate and breast cancer in which the disease can be either castrate resistant or occur post-menopausally, respectively. In these instances, the major precursor steroid of androgens and estrogens is dehydroepiandrosterone (DHEA) and DHEA-SO₄. This article reviews the major pathways by which adrenal steroids are converted to the potent male sex hormones, testosterone (T) and 5α-dihydrotestosterone (5α-DHT) and the discrete enzyme isoforms involved in castration resistant prostate cancer. Previous studies have mainly utilized radiotracers to investigate these pathways but have not used prevailing concentrations of precursors found in castrate male human serum. In addition, the full power of stable-isotope dilution liquid chromatography tandem mass spectrometry has not been applied routinely. Furthermore, it is clear that adaptive responses occur in the transporters and enzyme isoforms involved in response to androgen deprivation therapy that need to be considered.

Steroid sulfatase promotes invasion through epithelial-mesenchymal transition and predicts the progression of bladder cancer

Androgen signal has been recently suggested to be associated with the progression of bladder cancer. Steroid sulfatase (STS) is a steroid sulfate activation enzyme, considered to be one of the key enzymes in the androgen signaling pathway. However, the role of STS in bladder cancer has not been elucidated. The purpose of the present study was to determine the clinical and functional significance of STS in bladder cancer. Immunohistochemical analysis of surgical specimens obtained by radical cystectomy (n=114) demonstrated that overexpression of STS was associated with the invasion of bladder cancer, as evidenced by the incidence of STS-positive cancers (11.5 and 37.1% in non-muscle invasive and muscle invasive bladder cancers, respectively; P=0.003). STS-positive cancer demonstrated shorter recurrence-free survival and cancer-specific survival (P=0.0027 and 0.0030, respectively). Furthermore, knockdown of STS significantly reduced cell migration and invasion capacities of bladder cancer cells (P<0.001 and P=0.005, respectively), accompanied by the upregulation of E-cadherin and downregulation of vimentin. In summary, the present study demonstrated that STS promotes the invasion capability of bladder cancer via regulation of the epithelial-mesenchymal transition, and may be a useful marker for predicting the progression of bladder cancers.

Transporter for sulfated steroid hormones in the testis - expression pattern, biological significance and implications for fertility in men and rodents

In various tissues, steroid hormones may be sulfated, glucuronidated or otherwise modified. For a long time, these hydrophilic molecules have been considered to be merely inactive metabolites for excretion via bile or urine. Nevertheless, different organs such as the placenta and breast tissue produce large amounts of sulfated steroids. After the discovery of the enzyme steroid sulfatase, which is able to re-activate sulfated steroids, these precursor molecules entered the focus of interest again as a local supply for steroid hormone synthesis with a prolonged half-life compared to their unconjugated counterparts. The first descriptions of this so-called sulfatase pathway in the placenta and breast tissue (with special regards to hormone-dependent breast cancer) were quickly followed by studies of steroid sulfate production and function in the testis. These hydrophilic molecules may not permeate the cell membrane by diffusion in the way that unbound steroids can, but need to be transported through the plasma membrane by transport systems. In the testis, a functional sulfatase pathway requires the expression of specific uptake carrier and efflux transporters in testicular cells, i.e. Sertoli, Leydig and germ cells. Main focus has to be placed on Sertoli cells, as these cells build up the blood-testis barrier. In this review, an overview of carrier expression pattern in the human as well as rodent testis is provided with special interest towards implications on fertility.

Dehydroepiandrosterone (DHEA)-SO4 Depot and Castration-Resistant Prostate Cancer

Dehydroepiandrosterone (DHEA)-SO₄ of adrenal origin is the major C19 steroid in the serum. It is a precursor of intratumoral androgen biosynthesis in patients with advanced prostate cancer following chemical or surgical castration. DHEA is a product of the P450c17 (17α-hydroxylase-17,20-lyase) enzyme. Despite inhibition of P450c17 with new agents, e.g., Abiraterone acetate, Orterenol, and Galeterone, the level of enzyme inhibition rarely exceeds 90% leaving behind a significant depot for androgen biosynthesis within the tumor. For DHEA-SO₄ to be utilized there is uptake by organic anion transporter polypeptides, deconjugation catalyzed by steroid sulfatase, and adaptive upregulation of prostate steroidogenic enzymes that will convert DHEA into either testosterone or dihydrotestosterone. The depot of DHEA-SO₄ that remains after P450c17 inhibition and the adaptive responses that occur within the tumor to promote DHEA utilization contribute to mechanisms of drug resistance observed with P450c17 inhibitors. Knowledge of these mechanisms identify new targets for therapeutics that could be used to surmount drug resistance in prostate cancer.

The role of sulfated steroid hormones in reproductive processes

Sulfated steroid hormones, such as dehydroepiandrosterone sulfate or estrone-3-sulfate, have long been regarded as inactive metabolites as they cannot activate classical steroid receptors. Some of them are present in the blood circulation at quite high concentrations, but generally sulfated steroids exhibit low membrane permeation due to their hydrophilic properties. However, sulfated steroid hormones can actively be imported into specific target cells via uptake carriers, such as the sodium-dependent organic anion transporter SOAT, and, after hydrolysis by the steroid sulfatase (so-called sulfatase pathway), contribute to the overall regulation of steroid responsive organs. To investigate the biological significance of sulfated steroid hormones for reproductive processes in humans and animals, the research group "Sulfated Steroids in Reproduction" was established by the German Research Foundation DFG (FOR1369). Projects of this group deal with transport of sulfated steroids, sulfation of free steroids, desulfation by the steroid sulfatase, effects of sulfated steroids on steroid biosynthesis and membrane receptors as well as MS-based profiling of sulfated steroids in biological samples. This review and concept paper presents key findings from all these projects and provides a broad overview over the current research on sulfated steroid hormones in the field of reproduction.

Role of OATP transporters in steroid uptake by prostate cancer cells in vivo

BACKGROUND

Epidemiologic and in vitro studies suggest that SLCO-encoded organic anion transporting polypeptide (OATP) transporters influence the response of prostate cancer (PCa) to androgen deprivation by altering intratumor androgens. We have previously shown that castration-resistant metastases express multiple SLCO transporters at significantly higher levels than primary PCa, suggesting that OATP-mediated steroid transport is biologically relevant in advanced disease. However, whether OATP-mediated steroid transport can actually modify prostate tumor androgen levels in vivo has never been demonstrated.

METHODS

We sought to determine whether OATP-mediated steroid transport can measurably alter PCa androgen levels in vivo. We evaluated the uptake of dehydroepiandrosterone (DHEAS), E1S and testosterone in LNCaP cells engineered to express OATP1B1, 1B3, 2B1 or 4A1. We measured the uptake via administration of tritiated steroids to castrate mice bearing vector control or OATP1B1-, 2B1- or 4A1-expressing xenografts. We treated tumor-bearing mice with DHEAS and testosterone at physiologically relevant levels and measured intratumor accumulation of administered steroids by mass spectrometry.

RESULTS

OATP1B1- and 2B-expressing xenografts each showed a threefold increase in tritiated-DHEAS uptake vs vector controls (P=0.002 and P=0.036, respectively). At circulating DHEAS levels similar to those in abiraterone-treated men (~15 μg dl^-1), OATP1B1- and 2B1-expressing xenografts showed a 3.9-fold (P=0.057) and 1.9-fold (P=0.048) increase in tumor accumulation of DHEAS and a 1.6-fold (P=0.057) and 2.7-fold (P=0.095) increase in DHEA, respectively. At the substantial circulating testosterone levels found in eugonadal men, a consistent effect of OATP1B1, 2B1 or 4A1 on testosterone uptake in vivo was not detected.

CONCLUSIONS

OATP transporters measurably alter DHEAS uptake and intratumor androgen levels in prostate tumors in vivo, even at circulating androgen levels achieved in abiraterone-treated patients. These novel data emphasize the continued need to inhibit ligand-mediated androgen receptor signaling in PCa tumors, and support prospective evaluation of studies designed to test inhibition of OATP-mediated DHEAS uptake and utilization.

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.

Profiling intact steroid sulfates and unconjugated steroids in biological fluids by liquid chromatography-tandem mass spectrometry (LC-MS-MS)

Within the combined DFG research project "Sulfated Steroids in Reproduction" an analytical method was needed for determining sulfated and unconjugated steroids with highest specificity out of different biological matrices such as aqueous solution, cell lysate and serum. With regard to this analytical challenge, LC-MS-MS presents the technique of choice because it permits (1) analysis of the intact steroid conjugate, (2) allows for simultaneous determination of multiple analytes (profiling, targeted metabolomics approach) and (3) is independent of phenomena such as cross-reactivity. Sample work up consisted of incubation of sample with internal standards (deuterium labeled steroids) followed by solid phase extraction. Only serum samples required a protein precipitation step prior to solid phase extraction. The extract was divided in two parts: six steroid sulfates (E1S, E2S, AS, 16-OH-DHEAS, PREGS, DHEAS) were analyzed by C18aQ-ESI-MS-MS in negative ion mode and eleven unconjugated steroids (E3, 16-OH-DHEA, E1, E2, (4)A, DHEA, T, 17-OH-PREG, Prog, An, PREG) were analyzed by C18-APCI-MS-MS in positive ion mode. For steroid sulfates, we found high sensitivities with LoQ values ranging from 0.08 to 1 ng mL(-1). Unconjugated steroids showed LoQ values between 0.5 and 10 ng mL(-1). Calibration plots showed excellent linearity. Mean intra- and inter-assay CVs were 2.4% for steroid sulfates and 6.4% for unconjugated steroids. Accuracy - determined in a two-level spike experiment - showed mean relative errors of 5.9% for steroid sulfates and 6.1% for unconjugated steroids. In summary, we describe a novel LC-MS-MS procedure capable of profiling six steroid sulfates and eleven unconjugated steroids from various biological matrices.

Cloning and functional characterization of the mouse sodium-dependent organic anion transporter Soat (Slc10a6)

The sodium-dependent organic anion transporter SOAT is a member of the Solute Carrier Family SLC10. In man, this carrier is predominantly expressed in the testis and has transport activity for sulfoconjugated steroid hormones. Here, we report on cloning, expression analysis and functional characterization of the mouse Soat (mSoat) and compare its characteristics with the human SOAT carrier. Quantitative mRNA expression analysis for mSoat in male mice revealed very high expression in lung and further high expression in testis and skin. Immunohistochemical studies showed expression of the mSoat protein in bronchial epithelial cells of the lung, in primary and secondary spermatocytes as well as round spermatids within the seminiferous tubules of the testis, in the epidermis of the skin, and in the urinary epithelium of the bladder. Stably transfected mSoat-HEK293 cells revealed sodium-dependent transport for dehydroepiandrosterone sulfate (DHEAS), estrone-3-sulfate, and pregnenolone sulfate (PREGS) with apparent Km values of 60.3μM, 2.1μM, and 2.5μM, respectively. In contrast to human SOAT, which has a preference for DHEAS as a substrate, mSoat exhibits the highest transport rate for PREGS, likely reflecting differences in the steroid pattern between both species. In conclusion, although certain differences between human SOAT and mSoat exist regarding quantitative gene expression in endocrine and non-endocrine tissues, as well as in the transport kinetics for steroid sulfates, in general, both can be regarded as homologous carriers.

Inhibition of dehydroepiandosterone sulfate action in androgen-sensitive tissues by EM-1913, an inhibitor of steroid sulfatase

Steroid sulfatase (STS) plays an important role in the formation of estrogens and androgens by allowing the conversion of inactive circulating sulfated steroids into active hormones. These steroids support the development and growth of a number of hormone-dependent cancers, including prostate cancer. Here, we tested a non-estrogenic and non-androgenic inhibitor of steroid STS, namely EM-1913, with special attention to its potential use in the treatment of prostate cancer. After determining the required dosage of dehydroepiandrosterone sulfate (DHEAS) needed to stimulate the ventral prostate and seminal vesicles in castrated rats, we measured that EM-1913 partially (26%) and almost entirely blocked (81%) the stimulating effect of DHEAS on ventral prostates and seminal vesicles, respectively. In addition, the homogenization of these two tissues allowed us to confirm that they were completely deprived of STS activity following a treatment with EM-1913. This effect is also reflected in blood, since the plasma level of DHEAS was increased in animals treated with EM-1913, whereas the levels of dehydroepiandrosterone (DHEA) and dihydrotestosterone (DHT), two DHEAS metabolites, meanwhile decreased. From these results, we concluded that STS inhibitor EM-1913 is a good candidate for additional preclinical studies.

Membrane transporters for sulfated steroids in the human testis--cellular localization, expression pattern and functional analysis

Sulfated steroid hormones are commonly considered to be biologically inactive metabolites, but may be reactivated by the steroid sulfatase into biologically active free steroids, thereby having regulatory function via nuclear androgen and estrogen receptors which are widespread in the testis. However, a prerequisite for this mode of action would be a carrier-mediated import of the hydrophilic steroid sulfate molecules into specific target cells in reproductive tissues such as the testis. In the present study we detected predominant expression of the Sodium-dependent Organic Anion Transporter (SOAT), the Organic Anion Transporting Polypeptide 6A1, and the Organic Solute Carrier Partner 1 in human testis biopsies. All of these showed significantly lower or even absent mRNA expression in severe disorders of spermatogenesis (arrest at the level of spermatocytes or spermatogonia, Sertoli cell only syndrome). Only SOAT was significantly lower expressed in biopsies showing hypospermatogenesis. By use of immunohistochemistry SOAT was localized to germ cells at various stages in human testis biopsies showing normal spermatogenesis. SOAT immunoreactivity was detected in zygotene primary spermatocytes of stage V, pachytene spermatocytes of all stages (I–V), secondary spermatocytes of stage VI, and round spermatids (step 1 and step 2) in stages I and II. Furthermore, SOAT transport function for steroid sulfates was analyzed with a novel liquid chromatography tandem mass spectrometry procedure capable of profiling steroid sulfate molecules from cell lysates. With this technique, the cellular inward-directed SOAT transport was verified for the established substrates dehydroepiandrosterone sulfate and estrone-3-sulfate. Additionally, β-estradiol-3-sulfate and androstenediol-3-sulfate were identified as novel SOAT substrates.

Functional characterization of seven single-nucleotide polymorphisms of the steroid sulfatase gene found in a Japanese population

Steroid sulfatase (STS) is an enzyme that hydrolyzes steroid sulfates such as dehydroepiandrosterone sulfate (DHEA-S) and estrone sulfate. STS has a key role in the synthesis of steroid hormones in placenta and breast cancer cells. Recently, we have identified six novel single-nucleotide polymorphisms (SNPs) and one nonsynonymous SNP (V476M) in the STS gene in a Japanese population. To clarify the effects of SNPs in the 5'-flanking region or 5' untranslated region on transcriptional activity, a reporter gene assay was conducted. In addition, DHEA-S desulfatase activity of a variant (Met at codon 476)-type enzyme was compared with that of the wild (Wd)-type enzyme in COS-1 cells. The transcriptional activities were significantly decreased (155A) and increased (-2837A and -1588C) in MCF-7 cells. On the other hand, no significant difference was found in expression levels of STS protein or specific activities of DHEA-S desulfation between Wd and the variant enzymes. This is the first report on the effects of various SNPs in the STS gene detected in Japanese healthy subjects.

Sulfatase inhibitors: a patent review

INTRODUCTION

Steroid sulfatase (STS) converts sulfated hormones to free hormones of importance in hormone-dependent diseases such as breast cancer and endometriosis. Carbohydrate sulfatases degrade complex carbohydrates as part of normal cellular turnover; certain lysosomal storage disorders (LSDs) involve defective processing of sulfated glycosaminoglycans by mutant sulfatases.

AREAS COVERED

Aryl sulfamates have been developed as STS inhibitors, and STX64 and PGL2001 are under evaluation in Phase I and II clinical trials for treatment of endometrial and metastatic breast and prostate cancers and endometriosis. Dual-acting compounds have emerged that are aromatase inhibitors (AIs), selective estrogen receptor antagonists, or inhibitors of microtubule polymerization. Sulfamidase inhibitors as pharmacological chaperones to assist maturation of folding-defective mutants for the treatment of Sanfilippo type A disease are under investigation. Coverage: The patent literature after the mid-1990s.

EXPERT OPINION

The failure of STX64 in a Phase II monotherapy clinical trial should not dissuade further investigations in multidrug regimens, particularly in combination with AIs. The recent development of dual-acting compounds may enhance the potential for success in the clinic. Further investigations into aryl sulfamates are required to clarify the molecular mechanism of action; additionally, new reversible sulfatase inhibition concepts are needed for the development of pharmacological chaperones for sulfatase LSDs.

Enhanced expression of organic anion transporting polypeptides (OATPs) in androgen receptor-positive prostate cancer cells: possible role of OATP1A2 in adaptive cell growth under androgen-depleted conditions

The biological mechanisms underlying castration resistance of prostate cancer are not fully understood. In the present study, we examined the role of organic anion transporting polypeptides (OATPs) as importers of dehydroepiandrosterone sulfate (DHEAS) into cells to support growth under androgen-depleted conditions. Cell growth and mRNA expression of OATP genes were studied in human prostate cancer LNCaP and 22Rv1 cells under androgen-depleted conditions. The stimulatory effect of DHEAS on cell growth was investigated in LNCaP cells in which OATP1A2 had been silenced. Growth of both cell lines was stimulated by DHEAS and the effect was attenuated by STX64, an inhibitor of steroid sulfatase which can covert DHEAS to DHEA. OATP1A2 mRNA expression was increased most prominently among various genes tested in LNCaP cells grown in androgen-depleted medium. Similar results were obtained with 22Rv1 cells. Furthermore, the characteristics of [(3)H]DHEAS uptake by LNCaP cells were consistent with those of OATP-mediated transport. Knockdown of OATP1A2 in LNCaP cells resulted in loss of the DHEAS sensitivity of cell growth. Our results suggest that enhanced OATP1A2 expression is associated with adaptive cell growth of prostate cancer cells under androgen-depleted conditions. Thus, OATP1A2 may be a pharmacological target for prostate cancer treatment.

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.

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.

Steroid sulfatase: a new target for the endocrine therapy of breast cancer

Inhibitors of steroid sulfatase are being developed as a novel therapy for hormone-dependent breast cancer in postmenopausal women. Data suggest that steroid sulfatase (STS) activity is much higher than aromatase activity in breast tumors and high levels of STS mRNA expression in tumors are associated with a poor prognosis. STS hydrolyzes steroid sulfates, such as estrone sulfate and dehydroepiandrosterone sulfate (DHEAS), to estrone and DHEA, which can be converted to steroids with potent estrogenic properties, that is, estradiol and androstenediol, respectively. Several potent irreversible STS inhibitors have now been identified, including STX64 (BN83495), a tricyclic sulfamate ester. This drug recently completed the first-ever trial of this new type of therapy in postmenopausal women with estrogen receptor-positive metastatic breast cancer. STX64, tested at 5-mg and 20-mg doses, was able to almost completely block STS activity in peripheral blood lymphocytes and tumor tissues. Inhibition of STS activity was associated with significant reductions in serum concentrations of androstenediol and estrogens. Unexpectedly, serum androstenedione concentrations also decreased by up to 86%, showing that this steroid, which is the main substrate for the aromatase in postmenopausal women, is derived mainly from the peripheral conversion of DHEAS. Of eight patients who completed therapy, five showed evidence of stable disease for up to 7.0 months. This new endocrine therapy offers considerable potential for the treatment of hormone-dependent breast cancer in postmenopausal women.

Immunohistochemical analysis of steroid sulfatase in human tissues

Steroid sulfatase (EC 3.1.6.2) is an enzyme that removes the sulfate group from 3beta-hydroxysteroid sulfates. This enzyme is best known for its role in estrogen production via the fetal adrenal-placental pathway during pregnancy; however, it also has important functions in other physiological and pathological steroid pathways. The objective of this study was to examine the distribution of steroid sulfatase in normal human tissues and in breast cancers using immunohistochemistry, employing a newly developed steroid sulfatase antibody. A rabbit polyclonal antiserum was generated against a peptide representing a conserved region of the steroid sulfatase protein. In Western blotting experiments using human placental microsomes, this antiserum crossreacted with a 65 kDa protein, the reported size of steroid sulfatase. The antiserum also crossreacted with single protein bands in Western blots of microsomes from two human breast cancer cell lines (MDA-MB-231 and MCF-7) and from rat liver; however, there were some size differences in the immunoreactive bands among tissues. The steroid sulfatase antibody was used in immunohistochemical analyses of individual human tissue slides as well as a human tissue microarray. For single tissues, human placenta and liver showed strong positive staining against the steroid sulfatase antibody. ER+/PR+ breast cancers also showed relatively strong levels of steroid sulfatase immunoreactivity. Normal human breast showed moderate levels of steroid sulfatase immunoreactivity, while ER-/PR- breast cancer showed weak immunoreactivity. This confirms previous reports that steroid sulfatase is higher in hormone-dependent breast cancers. For the tissue microarray, most tissues showed some detectable level of steroid sulfatase immunoreactivity, but there were considerable differences among tissues, with skin, liver and lymph nodes having the highest immunoreactivity and brain tissues having the lowest. These data reveal the utility of immunohistochemistry in evaluation of steroid sulfatase activity among tissues. The newly developed antibody should be useful in studies of both humans and rats.

Steroid sulfatase and estrogen sulfotransferase in human prostate cancer

BACKGROUND

Estrogen sulfotransferase (EST) and steroid sulfatase (STS) are known to be involved in in situ estrogen production in estrogen dependent human cancer such as breast cancer, but unknown in prostate cancer.

MATERIALS AND METHODS

We first examined whether these enzymes above were expressed and actually involved in estrogen production and metabolism in prostate cancer cell lines (LNCaP, DU-145, and PC-3). We than examined the expression of EST and STS in human prostate cancer tissues obtained from surgery (n = 52) using immunohistochemistry.

RESULTS

mRNAs of both enzymes were detected in all prostate cancer cell lines examined, and the synthesis of estrone (E(1)) and estradiol (E(2)) was also confirmed in these cell lines. In addition, STS immunoreactivity was detected in 44 cases (85%) and EST in 39 cases (75%), respectively.

CONCLUSIONS

STS and EST are expressed and may be involved in local production and metabolism of estrogens in human prostate cancers.

Steroid sulfatase: molecular biology, regulation, and inhibition

Steroid sulfatase (STS) is responsible for the hydrolysis of aryl and alkyl steroid sulfates and therefore has a pivotal role in regulating the formation of biologically active steroids. The enzyme is widely distributed throughout the body, and its action is implicated in physiological processes and pathological conditions. The crystal structure of the enzyme has been resolved, but relatively little is known about what regulates its expression or activity. Research into the control and inhibition of this enzyme has been stimulated by its important role in supporting the growth of hormone-dependent tumors of the breast and prostate. STS is responsible for the hydrolysis of estrone sulfate and dehydroepiandrosterone sulfate to estrone and dehydroepiandrosterone, respectively, both of which can be converted to steroids with estrogenic properties (i.e., estradiol and androstenediol) that can stimulate tumor growth. STS expression is increased in breast tumors and has prognostic significance. The role of STS in supporting tumor growth prompted the development of potent STS inhibitors. Several steroidal and nonsteroidal STS inhibitors are now available, with the irreversible type of inhibitor having a phenol sulfamate ester as its active pharmacophore. One such inhibitor, 667 COUMATE, has now entered a phase I trial in postmenopausal women with breast cancer. The skin is also an important site of STS activity, and deficiency of this enzyme is associated with X-linked ichthyosis. STS may also be involved in regulating part of the immune response and some aspects of cognitive function. The development of potent STS inhibitors will allow investigation of the role of this enzyme in physiological and pathological processes.

6-[2-(adamantylidene)-hydroxybenzoxazole]-O-sulfamate, a steroid sulfatase inhibitor for the treatment of androgen- and estrogen-dependent diseases

Steroid sulfatase (STS) offers a new target for the treatment of steroid hormone-dependent diseases, such as breast and prostate cancer and androgen-dependent skin diseases. We here characterize a novel non-estrogenic inhibitor of the enzyme, namely 6-[2-(adamantylidene)-hydroxybenzoxazole]-O-sulfamate (AHBS), with special attention to its potential use in the treatment of acne. The compound blocks STS activity in homogenates of human skin with IC(50)=16 nM. Following a single oral dose (5 mg/kg) in rats, the compound blocks STS in the skin by 95% at 8 h, followed by recovery of activity over 5 days. Following topical application to the skin, both in vitro and in vivo, AHBS passes through the stratum corneum leading to inhibition of STS activity in the dermal compartment with rapid onset and long duration. Topical application of AHBS to Göttingen minipigs for a period of 2 weeks does not induce symptoms of ichthyosis as seen in STS-deficient human subjects, but leads to a reduction of sebum secretion to the skin surface. Based on these data, clinical studies with AHBS in acne patients are warranted, in order to verify the hypothesis on the importance of the sulfatase pathway in androgen-dependent skin diseases.