Prostate formation in a marsupial is mediated by the testicular androgen 5 alpha-androstane-3 alpha,17 beta-diol

PRKACB is a novel imprinted gene in marsupials

BACKGROUND

Genomic imprinting results in parent-of-origin-specific gene expression and, among vertebrates, is found only in therian mammals: marsupials and eutherians. A differentially methylated region (DMR), in which the methylation status of CpG dinucleotides differs between the two alleles, can mark the parental identity of imprinted genes. We developed a computational pipeline that detected CpG islands (CGIs) marked by both methylated and unmethylated signals in whole genome bisulfite sequencing data. This approach identified candidate marsupial DMRs in a publicly available koala methylome. One of these candidate DMRs was associated with PRKACB, a gene encoding the protein kinase A catalytic subunit beta. Nothing is known about the imprinting status of PRKACB in eutherian mammals although mutations of this gene are associated with endocrine neoplasia and other developmental disorders.

RESULTS

In the tammar wallaby and brushtail possum there was parent-of-origin-specific DNA methylation in the PRKACB DMR in which the maternal allele was methylated and the paternal allele was unmethylated. There were multiple RNAs transcribed from this locus. Allele-specific expression analysis identified paternal expression of a PRKACB lncRNA and an mRNA isoform. Comparison of the PRKACB gene start site between marsupials and eutherians demonstrated that the CGI is longer in marsupials. The PRKACB gene product functions in the same signalling pathway as the guanine nucleotide-binding protein alpha subunit encoded at the GNAS locus, a known eutherian imprinted gene. In a mouse methylome Gnas had three differentially methylated CGIs, while in the koala methylome the GNAS locus had two unmethylated CGIs.

CONCLUSIONS

We conclude that PRKACB is a novel, DMR-associated marsupial imprinted gene. Imprinting of PRKACB in marsupials and GNAS in eutherians may indicate a conserved selection pressure for imprinting of the protein kinase A signalling pathway in therians with the two lineages adapting by imprinting different genes.

Androgenic induction of penile features in postnatal female mouse external genitalia from birth to adulthood: Is the female sexual phenotype ever irreversibly determined?

Female mice were treated for 35 days from birth to 60 days postnatal (P0, [birth], P5, P10, P20 and adult [∼P60]) with dihydrotestosterone (DHT). Such treatment elicited profound masculinization the female external genitalia and development of penile features (penile spines, male urogenital mating protuberance (MUMP) cartilage, corpus cavernosum glandis, corporal body, MUMP-corpora cavernosa, a large preputial space, internal preputial space, os penis). Time course studies demonstrated that DHT elicited canalization of the U-shaped clitoral lamina to create a U-shaped preputial space, preputial lining epithelium and penile epithelium adorned with spines. The effect of DHT was likely due to signaling through androgen receptors normally present postnatally in the clitoral lamina and associated mesenchyme. This study highlights a remarkable male/female difference in specification and determination of urogenital organ identity. Urogenital organ identity in male mice is irreversibly specified and determined prenatally (prostate, penis, and seminal vesicle), whereas many aspects of the female urogenital organogenesis are not irreversibly determined at birth and in the case of external genitalia are not irreversibly determined even into adulthood, the exception being positioning of the female urethra, which is determined prenatally.

Molecular Basis of Prostate Cancer and Natural Products as Potential Chemotherapeutic and Chemopreventive Agents

Prostate cancer is the second most common malignant cancer in males. It involves a complex process driven by diverse molecular pathways that closely related to the survival, apoptosis, metabolic and metastatic characteristics of aggressive cancer. Prostate cancer can be categorized into androgen dependent prostate cancer and castration-resistant prostate cancer and cure remains elusive due to the developed resistance of the disease. Natural compounds represent an extraordinary resource of structural scaffolds with high diversity that can offer promising chemical agents for making prostate cancer less devastating and curable. Herein, those natural compounds of different origins and structures with potential cytotoxicity and/or in vivo anti-tumor activities against prostate cancer are critically reviewed and summarized according to the cellular signaling pathways they interfere. Moreover, the anti-prostate cancer efficacy of many nutrients, medicinal plant extracts and Chinese medical formulations were presented, and the future prospects for the application of these compounds and extracts were discussed. Although the failure of conventional chemotherapy as well as involved serious side effects makes natural products ideal candidates for the treatment of prostate cancer, more investigations of preclinical and even clinical studies are necessary to make use of these medical substances reasonably. Therefore, the elucidation of structure-activity relationship and precise mechanism of action, identification of novel potential molecular targets, and optimization of drug combination are essential in natural medicine research and development.

Six Decades of Research on Human Fetal Gonadal Steroids

Human fetal gonads acquire endocrine steroidogenic capabilities early during their differentiation. Genetic studies show that this endocrine function plays a central role in the sexually dimorphic development of the external genitalia during fetal development. When this endocrine function is dysregulated, congenital malformations and pathologies are the result. In this review, we explain how the current knowledge of steroidogenesis in human fetal gonads has benefited from both the technological advances in steroid measurements and the assembly of detailed knowledge of steroidogenesis machinery and its expression in human fetal gonads. We summarise how the conversion of radiolabelled steroid precursors, antibody-based assays, mass spectrometry, ultrastructural studies, and the in situ labelling of proteins and mRNA have all provided complementary information. In this review, our discussion goes beyond the debate on recommendations concerning the best choice between the different available technologies, and their degrees of reproducibility and sensitivity. The available technologies and techniques can be used for different purposes and, as long as all quality controls are rigorously employed, the question is how to maximise the generation of robust, reproducible data on steroid hormones and their crucial roles in human fetal development and subsequent functions.

Hormonal and Molecular Regulation of Phallus Differentiation in a Marsupial Tammar Wallaby

Congenital anomalies in phalluses caused by endocrine disruptors have gained a great deal of attention due to its annual increasing rate in males. However, the endocrine-driven molecular regulatory mechanism of abnormal phallus development is complex and remains largely unknown. Here, we review the direct effect of androgen and oestrogen on molecular regulation in phalluses using the marsupial tammar wallaby, whose phallus differentiation occurs after birth. We summarize and discuss the molecular mechanisms underlying phallus differentiation mediated by sonic hedgehog (SHH) at day 50 pp and phallus elongation mediated by insulin-like growth factor 1 (IGF1) and insulin-like growth factor binding protein 3 (IGFBP3), as well as multiple phallus-regulating genes expressed after day 50 pp. We also identify hormone-responsive long non-coding RNAs (lncRNAs) that are co-expressed with their neighboring coding genes. We show that the activation of SHH and IGF1, mediated by balanced androgen receptor (AR) and estrogen receptor 1 (ESR1) signalling, initiates a complex regulatory network in males to constrain the timing of phallus differentiation and to activate the downstream genes that maintain urethral closure and phallus elongation at later stages.

Hedgehog Signaling for Urogenital Organogenesis and Prostate Cancer: An Implication for the Epithelial-Mesenchyme Interaction (EMI)

Hedgehog (Hh) signaling is an essential growth factor signaling pathway especially in the regulation of epithelial-mesenchymal interactions (EMI) during the development of the urogenital organs such as the bladder and the external genitalia (EXG). The Hh ligands are often expressed in the epithelia, affecting the surrounding mesenchyme, and thus constituting a form of paracrine signaling. The development of the urogenital organ, therefore, provides an intriguing opportunity to study EMI and its relationship with other pathways, such as hormonal signaling. Cellular interactions of prostate cancer (PCa) with its neighboring tissue is also noteworthy. The local microenvironment, including the bone metastatic site, can release cellular signals which can affect the malignant tumors, and vice versa. Thus, it is necessary to compare possible similarities and divergences in Hh signaling functions and its interaction with other local growth factors, such as BMP (bone morphogenetic protein) between organogenesis and tumorigenesis. Additionally, this review will discuss two pertinent research aspects of Hh signaling: (1) the potential signaling crosstalk between Hh and androgen signaling; and (2) the effect of signaling between the epithelia and the mesenchyme on the status of the basement membrane with extracellular matrix structures located on the epithelial-mesenchymal interface.

Hormone-responsive genes in the SHH and WNT/β-catenin signaling pathways influence urethral closure and phallus growth

Environmental endocrine disruptors (EEDs) that affect androgen or estrogen activity may disrupt gene regulation during phallus development to cause hypospadias or a masculinized clitoris. We treated developing male tammar wallabies with estrogen and females with androgen from day 20-40 postpartum (pp) during the androgen imprinting window of sensitivity. Estrogen inhibited phallus elongation but had no effect on urethral closure and did not significantly depress testicular androgen synthesis. Androgen treatment in females did not promote phallus elongation but initiated urethral closure. Phalluses were collected for transcriptome sequencing at day 50 pp when they first become sexually dimorphic to examine changes in two signaling pathways, sonic hedgehog (SHH) and wingless-type MMTV integration site family (WNT)/β-catenin. SHH mRNA and β-catenin were predominantly expressed in the urethral epithelium in the tammar phallus, as in eutherian mammals. Estrogen treatment and castration of males induced an upregulation of SHH, while androgen treatment downregulated SHH. These effects appear to be direct since we detected putative estrogen receptor α (ERα) and androgen receptor (AR) binding sites near SHH. WNT5A, like SHH, was downregulated by androgen, while WNT4 was upregulated in female phalluses after androgen treatment. After estrogen treatment, WIF1 and WNT7A were both downregulated in male phalluses. After castration, WNT9A was upregulated. These results suggest that SHH and WNT pathways are regulated by both estrogen and androgen to direct the proliferation and elongation of the phallus during differentiation. Their response to exogenous hormones makes these genes potential targets of EEDs in the etiology of abnormal phallus development including hypospadias.

In silico and functional studies reveal novel loss-of-function variants of SRD5A2, but no variants explaining excess 5α-reductase activity

Androgens are steroid hormones essential for human male and female development. Steroid reductases 5α (SRD5As) are key enzymes in androgen biosynthesis. Mutations in the human SRD5A2 are known to cause loss-of-function and severe 46,XY undervirilization. Gain-of-function variants have been suggested in androgen excess syndromes, but have not been found so far. Therefore we searched for gain-of-function mutations in the human SRD5A2 gene which might explain hyperandrogenic disorders such as the polycystic ovary syndrome, premature adrenarche and prostate cancer. We screened databases for candidate variants and characterised them in silico with the help of a novel SRD5A2 model. We selected 9 coding SNPs (A49T, R50A, P106L, P106A, N122A, L167S, R168C, P173S, R227Q) that have not been described in manifesting individuals, and assessed their enzyme kinetic properties in HEK293 cells. SRD5A2 activity was assessed by conversion of testosterone (T), progesterone (Prog) and androstenedione (Δ4A) to their 5α-reduced metabolites. Variants R50A and P173S showed partial activity with substrates T (34% and 28%) and Δ4A (37% and 22%). With substrate Prog variants P106L, P106A, L167S and R168C in addition showed partial activity (15% to 64%). Functional testing of all other variants showed loss-of-function. As predicted in our in silico analysis, all coding SNPs affected enzyme activity, however none of them showed gain-of-function. Thus excess 5α-reductase activity might be rather regulated at the (post)-transcriptional and/or post-translational level. However through this work seven new coding SNPs were characterised which might be of clinical relevance. It is possible that individuals carrying these SNPs show a minor phenotype that is not yet identified.

Structural and Functional Biology of Aldo-Keto Reductase Steroid-Transforming Enzymes

Aldo-keto reductases (AKRs) are monomeric NAD(P)(H)-dependent oxidoreductases that play pivotal roles in the biosynthesis and metabolism of steroids in humans. AKR1C enzymes acting as 3-ketosteroid, 17-ketosteroid, and 20-ketosteroid reductases are involved in the prereceptor regulation of ligands for the androgen, estrogen, and progesterone receptors and are considered drug targets to treat steroid hormone-dependent malignancies and endocrine disorders. In contrast, AKR1D1 is the only known steroid 5β-reductase and is essential for bile-acid biosynthesis, the generation of ligands for the farnesoid X receptor, and the 5β-dihydrosteroids that have their own biological activity. In this review we discuss the crystal structures of these AKRs, their kinetic and catalytic mechanisms, AKR genomics (gene expression, splice variants, polymorphic variants, and inherited genetic deficiencies), distribution in steroid target tissues, roles in steroid hormone action and disease, and inhibitor design.

Alternative (backdoor) androgen production and masculinization in the human fetus

Masculinization of the external genitalia in humans is dependent on formation of 5α-dihydrotestosterone (DHT) through both the canonical androgenic pathway and an alternative (backdoor) pathway. The fetal testes are essential for canonical androgen production, but little is known about the synthesis of backdoor androgens, despite their known critical role in masculinization. In this study, we have measured plasma and tissue levels of endogenous steroids in second trimester human fetuses using multidimensional and high-resolution mass spectrometry. Results show that androsterone is the principal backdoor androgen in the male fetal circulation and that DHT is undetectable (<1 ng/mL), while in female fetuses, there are significantly lower levels of androsterone and testosterone. In the male, intermediates in the backdoor pathway are found primarily in the placenta and fetal liver, with significant androsterone levels also in the fetal adrenal. Backdoor intermediates, including androsterone, are only present at very low levels in the fetal testes. This is consistent with transcript levels of enzymes involved in the alternate pathway (steroid 5α-reductase type 1 [SRD5A1], aldo-keto reductase type 1C2 [AKR1C2], aldo-keto reductase type 1C4 [AKR1C4], cytochrome P450 17A1 [CYP17A1]), as measured by quantitative PCR (qPCR). These data identify androsterone as the predominant backdoor androgen in the human fetus and show that circulating levels are sex dependent, but also that there is little de novo synthesis in the testis. Instead, the data indicate that placental progesterone acts as substrate for synthesis of backdoor androgens, which occurs across several tissues. Masculinization of the human fetus depends, therefore, on testosterone and androsterone synthesis by both the fetal testes and nongonadal tissues, leading to DHT formation at the genital tubercle. Our findings also provide a solid basis to explain why placental insufficiency is associated with disorders of sex development in humans.

Fetal human masculinisation depends on testosterone production by the testes and an alternative “backdoor” androgen. This study shows that this androgen is likely to be androsterone, which is sexually dimorphic in the fetus but does not come from the testes; instead, synthesis probably depends on placental substrates.

The human penis starts to develop before birth from a structure called the genital tubercle. This process is dependent on the secretion of testosterone from the fetal testes and subsequent conversion of testosterone into dihydrotestosterone (DHT) by enzymes in the genital tubercle. Recently, an alternative "backdoor" route to the formation of DHT, which does not require testosterone, has also been shown to be essential for normal development of the human penis. In this study we provide evidence indicating that androsterone is the major backdoor androgen involved in human masculinization and that it is produced in nongonadal tissues. Steroid hormone levels were measured in the plasma of second trimester human fetuses, and testosterone and androsterone were the only androgens with higher levels in males than in females. Analysis of tissue steroid levels showed that plasma androsterone did not primarily originate from the testes but, instead, was probably formed in other tissues via metabolism of placental progesterone. These data indicate, therefore, that masculinization of the human fetus depends on steroid hormone secretion from both the testes and the placenta, and would explain why placental dysfunction is associated with disorders of sex development.

Simultaneous measurement of 18 steroids in human and mouse serum by liquid chromatography-mass spectrometry without derivatization to profile the classical and alternate pathways of androgen synthesis and metabolism

BACKGROUND

The recently identified alternate, or backdoor, pathway of DHT synthesis provides important novel information on androgen biosynthesis beyond the classical pathway. We report a rapid and versatile liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to simultaneously and accurately quantify key steroids in human or mouse serum involved in either the classical or backdoor androgen synthesis pathways.

METHODS

Serum (200 µL) fortified with isotopically labelled internal standards underwent liquid-liquid extraction (LLE) with MTBE and extracts were analysed on a LC-MS/MS. The targeted steroids for quantification were testosterone (T), dihydrotestosterone (DHT), 5α-androstane-3α,17β-diol (3α diol), 5α-androstane-3β,17β-diol (3β diol), dehydroepiandrosterone (DHEA), androstenedione (A4), androsterone (AD), estradiol (E2), estrone (E1), progesterone (P4), pregnenolone (P5), androstenediol (Adiol), 17-hydroxyprogesterone (17-OHP4) and 17-hydroxypregnenolone (17-OHP5), corticosterone (B), cortisol (F), allopregnanolone (Allo-P5) and dihydroprogesterone (DHP).

RESULTS

The limits of quantification (LOQ) were 5 pg/mL for E2 and E1, 25 pg/mL for T, 50 pg/mL for A4 and 0.10 ng/mL for DHT, 17OHP5, P4, P5, AD, Adiol, DHEA, AlloP5 and 0.20 ng/mL for 17OHP4, 3α diol, 3β diol, DHP, 0.25 ng/mL for B and 1 ng/mL for F. Accuracy, precision, reproducibility and recovery were within acceptable limits for bioanalytical method validation. The method is illustrated in human and mouse, male and female serum.

CONCLUSIONS

The presented method is sufficiently sensitive, specific and reproducible to meet the quality criteria for routine laboratory application for accurate quantitation of 18 steroid concentrations in male and female serum from humans or mice for the purpose of profiling androgen synthesis and metabolism pathways.

Androgen and Oestrogen Affect the Expression of Long Non-Coding RNAs During Phallus Development in a Marsupial

There is increasing evidence that long non-coding RNAs (lncRNAs) are important for normal reproductive development, yet very few lncRNAs have been identified in phalluses so far. Unlike eutherians, phallus development in the marsupial tammar wallaby occurs post-natally, enabling manipulation not possible in eutherians in which differentiation occurs in utero. We treated with sex steroids to determine the effects of androgen and oestrogen on lncRNA expression during phallus development. Hormonal manipulations altered the coding and non-coding gene expression profile of phalluses. We identified several predicted co-regulatory lncRNAs that appear to be co-expressed with the hormone-responsive candidate genes regulating urethral closure and phallus growth, namely IGF1, AR and ESR1. Interestingly, more than 50% of AR-associated coding genes and lncRNAs were also associated with ESR1. In addition, we identified and validated three novel co-regulatory and hormone-responsive lncRNAs: lnc-BMP5, lnc-ZBTB16 and lncRSPO4. Lnc-BMP5 was detected in the urethral epithelium of male phalluses and was downregulated by oestrogen in males. Lnc-ZBTB16 was downregulated by oestrogen treatment in male phalluses at day 50 post-partum (pp). LncRSPO4 was downregulated by adiol treatment in female phalluses but increased in male phalluses after castration. Thus, the expression pattern and hormone responsiveness of these lncRNAs suggests a physiological role in the development of the phallus.

Transition from androgenic to neurosteroidal action of 5α-androstane-3α, 17β-diol through the type A γ-aminobutyric acid receptor in prostate cancer progression

Androgen ablation is the standard of care prescribed to patients with advanced or metastatic prostate cancer (PCa) to slow down disease progression. Unfortunately, a majority of PCa patients under androgen ablation progress to castration-resistant prostate cancer (CRPC). Several mechanisms including alternative intra-prostatic androgen production and androgen-independent androgen receptor (AR) activation have been proposed for CRPC progression. Aldo-keto reductase family 1 member C3 (AKR1C3), a multi-functional steroid metabolizing enzyme, is specifically expressed in the cytoplasm of PCa cells; and positive immunoreactivity of the type A γ-aminobutyric acid receptor (GABA_AR), an ionotropic receptor and ligand-gated ion channel, is detected on the membrane of PCa cells. We studied a total of 72 radical prostatectomy cases by immunohistochemistry, and identified that 21 cases exhibited positive immunoreactivities for both AKR1C3 and GABA_AR. In the dual positive cancer cases, AKR1C3 and GABA_AR subunit α₁ were either expressed in the same cells or in neighboring cells. Among several possible substrates, AKR1C3 reduces 5α-dihydrotesterone (DHT) to form 5α-androstane-3α, 17β-diol (3α-diol). 3α-diol is a neurosteroid that acts as a positive allosteric modulator of the GABA_AR in the central nervous system (CNS). We examined the hypothesis that 3α-diol-regulated pathological effects in the prostate are GABA_AR-dependent, but are independent of the AR. In GABA_AR-positive, AR-negative human PCa PC-3 cells, 3α-diol significantly stimulated cell growth in culture and the in ovo chorioallantoic membrane (CAM) xenograft model. 3α-diol also up-regulated expression of the epidermal growth factor (EGF) family of growth factors and activation of EGF receptor (EGFR) and Src as measured by quantitative polymerase chain reaction and immunoblotting, respectively. Inclusion of GABA_AR antagonists reversed 3α-diol-stimulated tumor cell growth, expression of EGF family members, and activation of EGFR and Src to the level observed in untreated cells. Results from the present study suggest that 3α-diol may act as an alternative intra-prostatic neurosteroid that activates AR-independent PCa progression. The involvement of AKR1C3-mediated steroid metabolisms in modulating GABA_AR activation and promoting PCa progression requires continued studies.

Dihydrotestosterone synthesis pathways from inactive androgen 5α-androstane-3β,17β-diol in prostate cancer cells: Inhibition of intratumoural 3β-hydroxysteroid dehydrogenase activities by abiraterone

Intratumoural dihydrotestosterone (DHT) synthesis could be an explanation for castration resistance in prostate cancer (PC). By using liquid chromatography-mass spectrometry, we evaluated the intratumoral DHT synthesis from 5α-androstane-3β,17β-diol (3β-diol), which is inactive androgen metabolized from DHT. 3β-diol had biochemical potential to be converted to DHT via three metabolic pathways and could stimulate PC cell growth. Especially, 3β-diol was not only converted back to upstream androgens such as dehydroepiandrosterone (DHEA) or Δ5-androstenediol but also converted directly to DHT which is the main pathway from 3β-diol to DHT. Abiraterone had a significant influence on the metabolism of DHEA, epiandrosterone and 3β-diol, by the inhibition of the intratumoural 3β-hydroxysteroid dehydrogenase (3β-HSD) activities which is one of key catalysts in androgen metabolic pathway. The direct-conversion of 3β-diol to DHT was catalysed by 3β-HSD and abiraterone could inhibit this activity of 3β-HSD. These results suggest that PC had a mechanism of intratumoural androgen metabolism to return inactive androgen to active androgen and intratumoural DHT synthesis from 3β-diol is important as one of the mechanisms of castration resistance in PC. Additionally, the inhibition of intratumoural 3β-HSD activity could be a new approach to castration-resistant prostate cancer treatment.

Cortisol-Metabolizing Enzymes in Polycystic Ovary Syndrome

OBJECTIVE

The aim of this study was to assess the activity of cortisol-metabolizing enzymes in women with polycystic ovary syndrome (PCOS), using a fully quantitative gas chromatography/mass spectrometry (GCMS) method.

DESIGN

We investigated the glucocorticoid degradation pathways that include 11β-hydroxysteroid dehydrogenase (11β-HSD) type 1, 5α-reductase (5α-R) and 5β-reductase (5β-R), 3α-hydroxysteroid dehydrogenase, and 20α- and 20β-hydroxysteroid dehydrogenase (20α-HSD and 20β-HSD, respectively) in young nonobese women with PCOS, using a fully quantitative GCMS method.

SETTING

This study was conducted in a tertiary referral hospital in Israel.

PATIENTS

This study group consisted of 13 young women, aged 20.1 ± 2.8 years (mean ± SD), with the body mass index (BMI) of 22.6 ± 3.7 kg/m², diagnosed with PCOS according to the Rotterdam criteria. The control group consisted of 14 healthy young women matched for weight, height, and BMI.

INTERVENTIONS

Urine samples were analyzed using GCMS. We measured urinary steroid metabolites that represent the products and substrates of the study enzymes and calculated the product/substrate ratios to represent enzyme activity.

MAIN OUTCOME MEASURES

The calculation of enzymatic activity, based on glucocorticoid degradation metabolites, was done by GCMS in PCOS vs. controls.

RESULTS

All glucocorticoid degradation metabolites were higher in the PCOS group than in controls. Of the adrenal enzymes, the activities of 21-hydroxylase and 17α-hydroxylase were reduced, whereas the activity of 17,20-lyase was enhanced in PCOS. Of the degradation enzymes, the activity of 11β-HSD type 1 was reduced in women with PCOS only when calculated from cortoles and cortolones ratios. The activities of 5α-R/5β-R were increased only when calculating the 11-hydroxy metabolites of androgens. The activity of 20α-HSD was elevated in the patients with PCOS and its relation with the substrate levels was lost.

CONCLUSIONS

We confirm PCOS association with low 21-hydroxylase activity. PCOS is associated with dysregulation in glucocorticoid degradation. The activity of 5α-R is enhanced only through the backdoor pathway. Marked increase in the activity of 20α-HSD suggests a hitherto unknown derangement in PCOS.

Sex steroid profiles and pair-maintenance behavior of captive wild-caught zebra finches (Taeniopygia guttata)

Here, we studied the life-long monogamous zebra finch, to examine the relationship between circulating sex steroid profiles and pair-maintenance behavior in pairs of wild-caught zebra finches (paired in the laboratory for >1 month). We used liquid chromatography-tandem mass spectrometry to examine a total of eight androgens and progestins [pregnenolone, progesterone, dehydroepiandrosterone (DHEA), androstenediol, pregnan-3,17-diol-20-one, androsterone, androstanediol, and testosterone]. In the plasma, only pregnenolone, progesterone, DHEA, and testosterone were above the limit of quantification. Sex steroid profiles were similar between males and females, with only circulating progesterone levels significantly different between the sexes (female > male). Circulating pregnenolone levels were high in both sexes, suggesting that pregnenolone might serve as a circulating prohormone for local steroid synthesis in zebra finches. Furthermore, circulating testosterone levels were extremely low in both sexes. Additionally, we found no correlations between circulating steroid levels and pair-maintenance behavior. Taken together, our data raise several interesting questions about the neuroendocrinology of zebra finches.

FOXA1 and SOX9 Expression in the Developing Urogenital Sinus of the Tammar Wallaby (Macropus eugenii)

The mammalian prostate is a compact structure in humans but multi-lobed in mice. In humans and mice, FOXA1 and SOX9 play pivotal roles in prostate morphogenesis, but few other species have been examined. We examined FOXA1 and SOX9 in the marsupial tammar wallaby, Macropus eugenii, which has a segmented prostate more similar to human than to mouse. In males, prostatic budding in the urogenital epithelium (UGE) was initiated by day 24 postpartum (pp), but in the female the UGE remained smooth and had begun forming the marsupial vaginal structures. FOXA1 was upregulated in the male urogenital sinus (UGS) by day 51 pp, whilst in the female UGS FOXA1 remained basal. FOXA1 was localised in the UGE in both sexes between day 20 and 80 pp. SOX9 was upregulated in the male UGS at day 21-30 pp and remained high until day 51-60 pp. SOX9 protein was localised in the distal tips of prostatic buds which were highly proliferative. The persistent upregulation of the transcription factors SOX9 and FOXA1 after the initial peak and fall of androgen levels suggest that in the tammar, as in other mammals, these factors are required to sustain prostate differentiation, development and proliferation as androgen levels return to basal levels.

Morphological and functional maturation of Leydig cells: from rodent models to primates

BACKGROUND

Leydig cells (LC) are the sites of testicular androgen production. Development of LC occurs in the testes of most mammalian species as two distinct growth phases, i.e. as fetal and pubertal/adult populations. In primates there are indications of a third neonatal growth phase. LC androgen production begins in embryonic life and is crucial for the intrauterine masculinization of the male fetal genital tract and brain, and continues until birth after which it rapidly declines. A short post-natal phase of LC activity in primates (including human) termed 'mini-puberty' precedes the period of juvenile quiescence. The adult population of LC evolves, depending on species, in mid- to late-prepuberty upon reawakening of the hypothalamic-pituitary-testicular axis, and these cells are responsible for testicular androgen production in adult life, which continues with a slight gradual decline until senescence. This review is an updated comparative analysis of the functional and morphological maturation of LC in model species with special reference to rodents and primates.

METHODS

Pubmed, Scopus, Web of Science and Google Scholar databases were searched between December 2012 and October 2014. Studies published in languages other than English or German were excluded, as were data in abstract form only. Studies available on primates were primarily examined and compared with available data from specific animal models with emphasis on rodents.

RESULTS

Expression of different marker genes in rodents provides evidence that at least two distinct progenitor lineages give rise to the fetal LC (FLC) population, one arising from the coelomic epithelium and the other from specialized vascular-associated cells along the gonad-mesonephros border. There is general agreement that the formation and functioning of the FLC population in rodents is gonadotrophin-responsive but not gonadotrophin-dependent. In contrast, although there is in primates some controversy on the role of gonadotrophins in the formation of the FLC population, there is consensus about the essential role of gonadotrophins in testosterone production. Like the FLC population, adult Leydig cells (ALC) in rodents arise from stem cells, which have their origin in the fetal testis. In contrast, in primates the ALC population is thought to originate from FLC, which undergo several cycles of regression and redifferentiation before giving rise to the mature ALC population, as well as from differentiation of stem cells/precursor cells. Despite this difference in origin, both in primates and rodents the formation of the mature and functionally active ALC population is critically dependent on the pituitary gonadotrophin, LH. From studies on rodents considerable knowledge has emerged on factors that are involved besides LH in the regulation of this developmental process. Whether the same factors also play a role in the development of the mature primate LC population awaits further investigation.

CONCLUSION

Distinct populations of LC develop along the life span of males, including fetal, neonatal (primates) and ALC. Despite differences in the LC lineages of rodents and primates, the end product is a mature population of LC with the main function to provide androgens necessary for the maintenance of spermatogenesis and extra-gonadal androgen actions.

Regulation of local steroidogenesis in the brain and in prostate cancer: lessons learned from interdisciplinary collaboration

Sex steroids play critical roles in the regulation of the brain and many other organs. Traditionally, researchers have focused on sex steroid signaling that involves travel from the gonads via the circulation to intracellular receptors in target tissues. This classic concept has been challenged, however, by the growing number of cases in which steroids are synthesized locally and act locally within diverse tissues. For example, the brain and prostate carcinoma were previously considered targets of gonadal sex steroids, but under certain circumstances, these tissues can upregulate their steroidogenic potential, particularly when circulating sex steroid concentrations are low. We review some of the similarities and differences between local sex steroid synthesis in the brain and prostate cancer. We also share five lessons that we have learned during the course of our interdisciplinary collaboration, which brought together neuroendocrinologists and cancer biologists. These lessons have important implications for future research in both fields.

Wolffian duct development

The Wolffian ducts (WDs) are the progenitors of the epididymis, vas deferens and seminal vesicles. They form initially as nephric ducts that acquire connection to the developing testis as the mesonephros regresses. The development of the WDs is dependent on androgens. Conventionally, the active androgen is believed to be testosterone delivered locally rather than via the systemic circulation. However, recent studies in marsupials show that 5α-reduced steroids are essential and that these can induce virilisation even when they are delivered via the systemic circulation. The development of the WDs involves an interplay between the duct epithelium and underlying mesenchyme; androgen receptors in both the epithelium and mesenchyme are needed. The epidermal growth factor and epidermal growth factor receptor may play a role, possibly via activation of androgen receptor. The formation of the epididymis involves a complex morphogenetic program to achieve the normal pattern of coiling, formation of septae, and regional functional differentiation. In part, this process may be mediated by inhibin beta A as well as by genes from the HOX cluster. Whilst the development of the WD is androgen dependent, it is clear that there is a complex interplay between androgens, genes and growth factors in the tissues that leads to the formation of the complex anatomy of the male reproductive duct system in the adult.

Hormone-independent pathways of sexual differentiation

New observations over the last 25 years of hormone-independent sexual dimorphisms have gradually and unequivocally overturned the dogma, arising from Jost's elegant experiments in the mid-1900s, that all somatic sex dimorphisms in vertebrates arise from the action of gonadal hormones. Although we know that Sry, a Y-linked gene, is the primary gonadal sex determinant in mammals, more recent analysis in marsupials, mice, and finches has highlighted numerous sexual dimorphisms that are evident well before the differentiation of the testis and which cannot be explained by a sexually dimorphic hormonal environment. In marsupials, scrotal bulges and mammary primordia are visible before the testis has differentiated due to the expression of a gene(s) on the X chromosome. ZZ and ZW gynandromorph finches have brains that develop in a sexually dimorphic way dependent on their sex chromosome content. In genetically manipulated mice, it is the X chromosomes, not the gonads, that determine many characters including rate of early development, adiposity, and neural circuits. Even spotted hyenas have sexual dimorphisms that cannot be simply explained by hormonal exposure. This review discusses the recent findings that confirm that there are hormone-independent sexual dimorphisms well before the gonads begin to produce their hormones.

A dual role for SHH during phallus development in a marsupial

The mammalian phallus arises from identical primordia in both sexes and is patterned in part by the key morphogen Sonic hedgehog (SHH). We have investigated SHH and other morphogens during phallus development in the tammar wallaby. In this marsupial, testis differentiation and androgen production occurs just after birth, but it takes a further 50-60 days before the phallus becomes sexually dimorphic. One day before birth, SHH was expressed in both sexes in the urethral epithelium. In males, there was a marked upregulation of SHH, GLI2, and AR at day 50 postpartum, a time when testicular androgen production falls. SHH, GLI2, and AR were downregulated in female pouch young treated with androstanediol from days 24-50, but not when treatments were begun at day 29, suggesting an early window of androgen sensitivity. SHH, GLI2, and AR expression in the phallus of males castrated at day 23 did not differ from controls, but there was an increase in SHH and GLI2 and a decrease in FGF8 and BMP4 expression when the animals were castrated at day 29. These results suggest that the early patterning by SHH is androgen-independent followed by an androgen-dependent window of sensitivity and a sharp rise in SHH expression after androgen withdrawal at day 50.

Androgen deprivation promotes intratumoral synthesis of dihydrotestosterone from androgen metabolites in prostate cancer

Intratumoral synthesis of dihydrotestosterone (DHT) from precursors cannot completely explain the castration resistance of prostate cancer. We showed that DHT was intratumorally synthesized from the inactive androgen metabolites 5α-androstane-3α/β,17β-diol (3α/β-diol) in prostate cancer cells via different pathways in a concentration-dependent manner. Additionally, long-term culture in androgen-deprived media increased transcriptomic expression of 17β-hydroxysteroid dehydrogenase type 6 (HSD17B6), a key enzyme of oxidative 3α-HSD that catalyzes the conversion of 3α-diol to DHT in prostate cancer cells. Correspondingly, the score for HSD17B6 in tissues of 42 prostate cancer patients undergoing androgen deprivation therapy (ADT) was about 2-fold higher than that in tissues of 100 untreated individuals. In men receiving ADT, patients showing biochemical progression had a higher HSD17B6 score than those without progression. These results suggested that 3α/β-diol also represent potential precursors of DHT, and the back conversion of DHT from androgen derivatives can be a promising target for combination hormone therapy.

Minireview: Androgen metabolism in castration-resistant prostate cancer

The decades-old terminology of androgen independence has been replaced in recent years with castration-resistant prostate cancer. Biological and clinical evidence have together conspired to support the use of this revised terminology by demonstrating that in the vast majority of cases tumors are neither truly depleted of androgens, nor are they free of the requirement for androgens to sustain growth and progression. Abiraterone acetate, an androgen synthesis inhibitor, and enzalutamide, a potent androgen receptor antagonist, both exploit the continued requirement for androgens. A central question, given the therapeutic gains enabled by further suppression of the androgen axis with these newer agents, is whether there may be additional clinical benefit gained by moving the goal posts of androgen suppression even further. The answer lies in part with the mechanisms utilized by tumors that enable resistance to these therapies. The aims of this review were to give a broad outline of steroidogenesis in prostate cancer and to highlight recent developments in understanding resistance to hormonal therapies.

Maturation of the growth axis in marsupials occurs gradually during post-natal life and over an equivalent developmental stage relative to eutherian species

The separation of a nutrition-responsive insulin-like growth factor (IGF) system and a growth hormone (GH) responsive IGF system to control pre- and post-natal growth of developing mammals may originate from the constraints imposed by intra-uterine development. In eutherian species that deliver relatively precocial young, maturation of the GH regulatory system is coincident with the time of birth. We measured the hepatic expression of the four key growth axis genes GH-receptor, IGF-1 and -2, and IGFBBP-3, and plasma protein concentrations of IGF-1 from late fetal life through to adult stages of a marsupial, the tammar wallaby. The data clearly show that maturation of GH-regulated growth in marsupials occurs gradually over the course of post-natal life at an equivalent developmental stage to that of precocial eutherian mammals. This suggests that the timing of GH-regulated growth in marsupials is not related to parturition but instead to the relative developmental stage.

Development of the penile urethra in the tammar wallaby

Hypospadias is increasingly common, and requires surgery to repair, but its aetiology is poorly understood. The marsupial tammar wallaby provides a unique opportunity to study hypospadias because penile differentiation occurs postnatally. Androgens are responsible for penile development in the tammar, but the majority of differentiation, in particular formation and closure of the urethral groove forming the penile urethra in males, occurs when there is no measurable sex difference in the concentrations of testosterone or dihydrotestosterone in either the gonads or the circulation [corrected]. Phalluses were examined morphologically from the sexually indifferent period (when androgens are high) to well after the time that the phallus becomes sexually dimorphic. We show that penile development and critical changes in the positioning of the urethra occur in the male phallus begin during an early window of time when androgens are high. Remodelling of the urethra in the male occurs between days 20-60. The critical period of time for the establishment urethral closure occurs during the earliest phases of penile development. This study suggests that there is an early window of time before day 60 when androgen imprinting must occur for normal penile development and closure of the urethral groove.

The critical role of androgens in prostate development

Androgens are involved in every aspect of prostate development, growth, and function from early in male embryogenesis to prostatic hyperplasia in aging men and dogs. Likewise, androgen deprivation at any phase of life causes a decrease in prostate cell number and DNA content. The process by which the circulating androgen testosterone is converted to dihydrotestosterone in the tissue and dihydrotestosterone in turn gains access to the nucleus where it regulates gene expression, largely via interaction with a receptor protein, is understood, but the downstream control mechanisms by which hormonal signals are translated into differentiation, growth, and function are being unraveled.

Potential prostate cancer drug target: bioactivation of androstanediol by conversion to dihydrotestosterone

High-affinity binding of dihydrotestosterone (DHT) to the androgen receptor (AR) initiates androgen-dependent gene activation, required for normal male sex development in utero, and contributes to prostate cancer development and progression in men. Under normal physiologic conditions, DHT is synthesized predominantly by 5α-reduction of testosterone, the major circulating androgen produced by the testis. During androgen deprivation therapy, intratumoral androgen production is sufficient for AR activation and prostate cancer growth, even though circulating testicular androgen levels are low. Recent studies indicate that the metabolism of 5α-androstane-3α, 17β-diol by 17β-hydroxysteroid dehydrogenase 6 in benign prostate and prostate cancer cells is a major biosynthetic pathway for intratumoral synthesis of DHT, which binds AR and initiates transactivation to promote prostate cancer growth during androgen deprivation therapy. Drugs that target the so-called backdoor pathway of DHT synthesis provide an opportunity to enhance clinical response to luteinizing-hormone-releasing hormone (LHRH) agonists or antagonists, AR antagonists, and inhibitors of 5α-reductase enzymes (finasteride or dutasteride), and other steroid metabolism enzyme inhibitors (ketoconazole or the recently available abiraterone acetate).

Transcriptional regulation of type 11 17β-hydroxysteroid dehydrogenase expression in prostate cancer cells

Type 11 hydroxysteroid (17-beta) dehydrogenase (HSD17B11) catalyzes the conversion of 5α-androstan-3α,17β-diol into androsterone suggesting that it may play an important role in androgen metabolism. We previously described that overexpression of C/EBPα or C/EBPβ induced HSD17B11 expression in HepG2 cells but this process was not mediated by the CCAAT boxes located within its proximal promoter region. Here, we study HSD17B11 transcriptional regulation in prostate cancer (PC) cells. Transfection experiments showed that the region -107/+18 is sufficient for promoter activity in PC cells. Mutagenesis analysis indicated that Sp1 and C/EBP binding sites found in this region are essential for promoter activity. Additional experiments demonstrated that ectopic expression of Sp1 and C/EBPα upregulated HSD17B11 expression only in PC cell lines. Through DAPA and ChIP assays, specific recruitment of Sp1 and C/EBPα to the HSD17B11 promoter was detected. These results show that HSD17B11 transcription in PC cells is regulated by Sp1 and C/EBPα.

Activation of the androgen receptor by intratumoral bioconversion of androstanediol to dihydrotestosterone in prostate cancer

The androgen receptor (AR) mediates the growth of benign and malignant prostate in response to dihydrotestosterone (DHT). In patients undergoing androgen deprivation therapy for prostate cancer, AR drives prostate cancer growth despite low circulating levels of testicular androgen and normal levels of adrenal androgen. In this report, we demonstrate the extent of AR transactivation in the presence of 5α-androstane-3α,17β-diol (androstanediol) in prostate-derived cell lines parallels the bioconversion of androstanediol to DHT. AR transactivation in the presence of androstanediol in prostate cancer cell lines correlated mainly with mRNA and protein levels of 17β-hydroxysteroid dehydrogenase 6 (17β-HSD6), one of several enzymes required for the interconversion of androstanediol to DHT and the inactive metabolite androsterone. Levels of retinol dehydrogenase 5, and dehydrogenase/reductase short-chain dehydrogenase/reductase family member 9, which also convert androstanediol to DHT, were lower than 17β-HSD6 in prostate-derived cell lines and higher in the castration-recurrent human prostate cancer xenograft. Measurements of tissue androstanediol using mass spectrometry demonstrated androstanediol metabolism to DHT and androsterone. Administration of androstanediol dipropionate to castration-recurrent CWR22R tumor-bearing athymic castrated male mice produced a 28-fold increase in intratumoral DHT levels. AR transactivation in prostate cancer cells in the presence of androstanediol resulted from the cell-specific conversion of androstanediol to DHT, and androstanediol increased LAPC-4 cell growth. The ability to convert androstanediol to DHT provides a mechanism for optimal utilization of androgen precursors and catabolites for DHT synthesis.

"Getting from here to there"--mechanisms and limitations to the activation of the androgen receptor in castration-resistant prostate cancer

Despite the clinical regression that typifies the initial response of advanced prostate cancer to gonadal testosterone depletion, tumors eventually progress. However, evidence supports the concept that signaling via the androgen receptor (AR) is important in progression to castration-resistant prostate cancer (CRPC).Steroid hormones are synthesized from cholesterol in a series of tightly regulated steps involving the cleavage of carbon-carbon bonds, the introduction of functional groups derived from activated molecular oxygen, and the oxidation and reduction of carbon-carbon and carbon-oxygen bonds. In the adrenal cortex and gonads, steroidogenesis is tightly regulated, very efficient, and highly directional. In contrast, steroid metabolism in peripheral tissues is characterized by competing enzymes and pathways, low efficiency, and great variability. Many steps are mechanistically and functionally irreversible, but some are not, and the repertoire of specific enzymes, intracellular redox state, and access to hormone precursors all contribute to steroid flux and accumulation.The investigation of steroid metabolizing enzymes in CRPC often assumes that the pathways and the patterns of metabolism mirror those defined in the adrenals and the gonads and validated by human deficiency syndromes. Unfortunately, several potential pathways using different enzymes might contribute substantially to androgen synthesis in CRPC. Finally, a number of mechanisms have been reported by which the AR is activated independent of ligand. Recent observations have suggested that AR forms with constitutive activity occur in CRPC, stimulating transcription without a requirement for ligand. This overview outlines a broad view of how the mechanisms by which the AR may be activated, whether by alternate pathways of androgen synthesis or the production of alternate forms of the AR, with an emphasis on what aspects must be accounted for when using model systems to explore the biology of human prostate cancer.

Measurement of sex steroids in murine blood and reproductive tissues by liquid chromatography-tandem mass spectrometry

Accurate measurement of sex steroids is essential to evaluate mouse models for human reproductive development and disorders. The recent advent of liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays that match the sensitivity of steroid immunoassay could overcome problems arising from the limited specificity of steroid immunoassay. In this current study we validate a LC-MS/MS assay for the measurement of key sex steroids from murine serum and reproductive tissues. The assay gave excellent dilutional linearity (r(2)> or =0.98) and reproducibility (CV< or =10% of replicate samples) in serum and reproductive tissues with sensitive quantitation limits; testosterone (T; 2pg), dihydrotestosterone (DHT; 10pg), 5alpha-androstane-3alpha,17beta-diol (3alphaDiol; 40pg), 5alpha-androstane-3beta,17beta-diol (3betaDiol; 40pg), estradiol (E2; 0.5pg) and estrone (E1; 0.3pg). Using 0.1mL sample, T was the only consistently detectable steroid (detection limit 20pg/ml) in both male and female mouse serum. In the testis, T and DHT were quantifiable as were both diols at relatively high levels. Prostatic T levels were low and DHT was determined to be the most abundant androgen in this tissue. Uterine and ovarian levels of E2, E1 and T were measurable, with levels varying according to estrous cycle stage. Hence, we demonstrate that this LC-MS/MS method has the sensitivity, specificity and multi-analyte capability to offer accurate steroid profiling in mouse serum and reproductive tissues.

New frontiers in androgen biosynthesis and metabolism

PURPOSE OF REVIEW

To summarize recent advances in androgen biosynthesis and metabolism in peripheral tissues (e.g., liver and prostate) and how these can be exploited therapeutically.

RECENT FINDINGS

Human liver catalyzes the reduction of circulating testosterone to yield four stereoisomeric tetrahydrosteroids. Recent advances have assigned the enzymes responsible for these reactions and elucidated their structural biology. Data also suggest that for 5alpha-dihydrotestosterone (5alpha-DHT), conjugation reactions (phase II) may precede ketosteroid reduction (phase I) reactions. Human prostate is the site of benign prostatic hyperplasia and prostate cancer, which occur in the aging male. Although the importance of local androgen biosynthesis in these diseases is accepted, recent advances have identified enzymes that regulate ligand access to the androgen-receptor; a 'backdoor pathway' to 5alpha-DHT that does not require testosterone acting as an intermediate; and the finding that castrate-resistant prostate cancer (CRPC) has undergone an adaptive response to androgen deprivation, which involves intratumoral testosterone and 5alpha-DHT biosynthesis that can be targeted using inhibitors of (CYP17-hydroxylase/17,20-lyase), aldo-keto reductase 1C3, and 5alpha-reductase type 1 and type 2.

SUMMARY

Enzyme isoforms responsible for the biosynthesis and metabolism of androgens in liver and prostate have been identified and those responsible for the biosynthesis of androgens in CRPC can be therapeutically targeted.

CYP7B1-mediated metabolism of 5alpha-androstane-3alpha,17beta-diol (3alpha-Adiol): a novel pathway for potential regulation of the cellular levels of androgens and neurosteroids

The current study presents data indicating that 5alpha-androstane-3alpha,17beta-diol (3alpha-Adiol) undergoes a previously unknown metabolism into hydroxymetabolites, catalyzed by CYP7B1. 3alpha-Adiol is an androgenic steroid which serves as a source for the potent androgen dihydrotestosterone and also can modulate gamma-amino butyric acid A (GABA(A)) receptor function in the brain. The steroid hydroxylase CYP7B1 is known to metabolize cholesterol derivatives, sex hormone precursors and certain estrogens, but has previously not been thought to act on androgens or 3alpha-hydroxylated steroids. 3alpha-Adiol was found to undergo NADPH-dependent metabolism into 6- and 7-hydroxymetabolites in incubations with porcine microsomes and human kidney-derived HEK293 cells, which are high in CYP7B1 content. This metabolism was suppressed by addition of steroids known to be metabolized by CYP7B1. In addition, 3alpha-Adiol significantly suppressed CYP7B1-mediated catalytic reactions, in a way as would be expected for substrates that compete for the same enzyme. Recombinant expression of human CYP7B1 in HEK293 cells significantly increased the rate of 3alpha-Adiol hydroxylation. Furthermore, the observed hydroxylase activity towards 3alpha-Adiol was very low or undetectable in livers of Cyp7b1(-/-) knockout mice. The present results indicate that CYP7B1-mediated catalysis may play a role for control of the cellular levels of androgens, not only of estrogens. These findings suggest a previously unknown mechanism for metabolic elimination of 3alpha-Adiol which may impact intracellular levels of dihydrotestosterone and GABA(A)-modulating steroids.

Formation of 5alpha-reduced androgens in the testes and urogenital tract of the grey short-tailed opossum, Monodelphis domestica

Testicular 5alpha-reduced androgens, largely 5alpha-androstane-3alpha,17beta-diol (androstanediol), are responsible for virilisation of pouch young in one marsupial (the tammar wallaby), but are not formed until later in development in another marsupial (the brushtail possum) and in rodents. Because the mechanism of virilisation of the urogenital tract in the grey short-tailed opossum Monodelphis domestica has never been defined, androgen formation and metabolism were investigated in this species. Testis fragments from grey short-tailed opossums of a wide range of ages were incubated with [3H]-progesterone and the metabolites were separated by high-performance liquid chromatography (HPLC). The only 19-carbon metabolites identified in the youngest ages (5-26 days) and the major metabolites in adult testes were testosterone and androstenedione. At 30, 42 and 49 days of age, dihydrotestosterone and small amounts of androstanediol were present. Time-sequence studies indicated that dihydrotestosterone and androstanediol were formed from the 5alpha-reduction (and 3-keto reduction) of testosterone. In a second series of experiments, tissue fragments of a variety of urogenital tract tissues were incubated with [3H]-testosterone and the metabolites separated by HPLC. During the interval in which male urogenital tract differentiation takes place in this species (between Days 15 and 28), the major metabolite identified was dihydrotestosterone. We conclude that the timing of 5alpha-reductase expression in the testes of the grey short-tailed possum resembles that of rodents and the brushtail possum rather than that of the tammar wallaby and that dihydrotestosterone is probably the intracellular androgen responsible for virilisation of the urogenital tract in this species.

Non-traditional metabolic pathways of adrenal steroids

Metabolic pathways are reconstructed from biochemical evidence to conceptualize the predominant route to important biomolecules. Pathways have heuristic value in their capacity to explain the metabolic derangements in genetic diseases of enzyme deficiencies and during pharmacologic inhibition of these enzymes. Implicit in the description of these pathways is the potential existence of alternate routes, variable order of reactions, and the inevitable by-products generated by incomplete efficiencies and competing enzymes. This chapter will consider alternate fates encountered by steroid hormone precursors in the adrenal gland, the variables influencing flux through these secondary pathways, and the significance of these diversions in health and disease.

5alpha-androstane-3alpha,17beta-diol supports human prostate cancer cell survival and proliferation through androgen receptor-independent signaling pathways: implication of androgen-independent prostate cancer progression

Androgen and androgen receptor (AR) are involved in growth of normal prostate and development of prostatic diseases including prostate cancer. Androgen deprivation therapy is used for treating advanced prostate cancer. This therapeutic approach focuses on suppressing the accumulation of potent androgens, testosterone and 5alpha-dihydrotestosterone (5alpha-DHT), or inactivating the AR. Unfortunately, the majority of patients with prostate cancer eventually advance to androgen-independent states and no longer respond to the therapy. In addition to the potent androgens, 5alpha-androstane-3alpha,17beta-diol (3alpha-diol), reduced from 5alpha-DHT through 3alpha-hydroxysteroid dehydrogenases (3alpha-HSDs), activated signaling may represent a novel pathway responsible for the progression to androgen-independent prostate cancer. Androgen sensitive human prostate cancer LNCaP cells were used to compare 5alpha-DHT and 3alpha-diol activated androgenic effects. In contrast to 5alpha-DHT, 3alpha-diol regulated unique patterns of beta-catenin and Akt expression as well as Akt phosphorylation in parental and in AR-silenced LNCaP cells. More significantly, 3alpha-diol, but not 5alpha-DHT, supported AR-silenced LNCaP cells and AR negative prostate cancer PC-3 cell proliferation. 3alpha-diol-activated androgenic effects in prostate cells cannot be attributed to the accumulation of 5alpha-DHT, since 5alpha-DHT formation was not detected following 3alpha-diol administration. Potential accumulation of 3alpha-diol, as a result of elevated 3alpha-HSD expression in cancerous prostate, may continue to support prostate cancer growth in the presence of androgen deprivation. Future therapeutic strategies for treating advanced prostate cancer might need to target reductive 3alpha-HSD to block intraprostatic 3alpha-diol accumulation.

5alpha-androstane-3alpha,17beta-diol selectively activates the canonical PI3K/AKT pathway: a bioinformatics-based evidence for androgen-activated cytoplasmic signaling

5alpha-Androstane-3alpha,17beta-diol (3alpha-diol) is reduced from the potent androgen, 5alpha-dihydrotestosterone (5alpha-DHT), by reductive 3alpha-hydroxysteroid dehydrogenases (3alpha-HSDs) in the prostate. 3alpha-diol is recognized as a weak androgen with low affinity toward the androgen receptor (AR), but can be oxidized back to 5alpha-DHT. However, 3alpha-diol may have potent effects by activating cytoplasmic signaling pathways, stimulating AR-independent prostate cell growth, and, more importantly, providing a key signal for androgen-independent prostate cancer progression. A cancer-specific, cDNA-based membrane array was used to determine 3alpha-diol-activated pathways in regulating prostate cancer cell survival and/or proliferation. Several canonical pathways appeared to be affected by 3alpha-diol-regulated responses in LNCaP cells; among them are apoptosis signaling, PI3K/AKT signaling, and death receptor signaling pathways. Biological analysis confirmed that 3alpha-diol stimulates AKT activation; and the AKT pathway can be activated independent of the classical AR signaling. These observations sustained our previous observations that 3alpha-diol continues to support prostate cell survival and proliferation regardless the status of the AR. We provided the first systems biology approach to demonstrate that 3alpha-diol-activated cytoplasmic signaling pathways are important components of androgen-activated biological functions in human prostate cells. Based on the observations that levels of reductive 3alpha-HSD expression are significantly elevated in localized and advanced prostate cancer, 3alpha-diol may, therefore, play a critical role for the transition from androgen-dependent to androgen-independent prostate cancer in the presence of androgen deprivation.

Pre-receptor regulation of the androgen receptor

The human androgen receptor (AR) is a ligand-activated nuclear transcription factor and mediates the induction of genes involved in the development of the male phenotype and male secondary sex characteristics, as well as the normal and abnormal growth of the prostate. We have identified the pair of hydroxysteroid dehydrogenases (HSDs) that regulate ligand access to the AR in human prostate. We find that type 3 3alpha-HSD (aldo-keto reductase (AKR)1C2) catalyzes the NADPH dependent reduction of the potent androgen 5alpha-dihydrotestosterone (5alpha-DHT) to yield the inactive androgen 3alpha-androstanediol (3alpha-diol). We also find that RoDH like 3alpha-HSD (RL-HSD) catalyzes the NAD(+) dependent oxidation of 3alpha-diol to yield 5alpha-DHT. Together these enzymes are involved in the pre-receptor regulation of androgen action. Inhibition of AKR1C2 would be desirable in cases of androgen insufficiency and inhibition of RL-HSD might be desirable in benign prostatic hyperplasia.

The functional development of Leydig cells in a marsupial

Leydig cells are the major source of androgen in the male mammal. We describe here for the first time the development of the Leydig cell in a macropodid marsupial, the tammar wallaby, Macropus eugenii. Leydig cells are first recognized morphologically 2 days after birth with the appearance of lipid droplets in the cytoplasm of certain interstitial cells. Lipid content closely matches the steroid content of the developing testis and marks the maturation of the steroid synthesis pathway in the tammar testis. Morphologically mature Leydig cells, marked by distinct mitochondria with tubular cristae and an extensive anastomosing network of smooth endoplasmic reticulum, are developed by day 10 after birth - the time of peak testosterone content in perinatal tammar testes. The volume percentage of each cell type in the testis does not change over time so the growth of each cellular component keeps pace with growth of the whole testis. There was no morphological or quantitative evidence of a change from one population of Leydig cells to another in the tammar testis as has been reported in several other species including the rat, mouse and human. Maturation of the testis is also marked by the development of tight junctions between the cell membranes of adjacent Sertoli cells. These appear around day 30 after birth and coincide with the onset of mitotic arrest in male germ cells. Overall, the development of the Leydig cell in the tammar wallaby follows a similar pattern to that seen in other mammals, although the start of Leydig cell differentiation is, like many other organ systems in marsupials, post natal, not fetal and there appears to be only a single population of Leydig cells.

Basic concepts and recent developments in human steroid hormone biosynthesis

The biosynthesis of steroid hormones requires the coordinated expression of the enzymes that comprise the pathways via which specific hormones are synthesized. These pathways and their associated enzymes are typically subject to regulation consisting of trophic hormone stimuli and feedback mechanisms. Very few tissues contribute substantially to de novo steroidogenesis, primarily the adrenal glands, the gonads, and the placenta. Both the embryonic origins and the signaling mechanisms for the adrenals and gonads are similar, and steroid synthesis in these two glands are the major focus of this review. We will further describe peripheral steroid metabolism and the regulation of steroid hormone potency in target tissues. In addition, we will briefly discuss the congenital adrenal hyperplasias to illustrate the principles developed in the initial sections. Finally, we will discuss some recent developments in steroidogensis, focusing on cytochrome P450 oxidoreductase deficiency and the alternate or "backdoor" pathway to dihydrotestosterone. We will conclude with a description of aberrant signaling mechanisms observed in adrenal tumors as a further example of how these pathways can be disturbed in pathologic states.

Identification of the molecular switch that regulates access of 5alpha-DHT to the androgen receptor

Pairs of hydroxysteroid dehydrogenases (HSDs) govern ligand access to steroid receptors in target tissues and act as molecular switches. By acting as reductases or oxidases, HSDs convert potent ligands into their cognate inactive metabolites or vice versa. This pre-receptor regulation of steroid hormone action may have profound effects on hormonal response. We have identified the HSDs responsible for regulating ligand access to the androgen receptor (AR) in human prostate. Type 3 3alpha-hydroxysteroid dehydrogenase (aldo-keto reductase 1C2) acts solely as a reductase to convert 5alpha-dihydrotestosterone (DHT), a potent ligand for the AR (K(d)=10(-11)M for the AR), to the inactive androgen 3alpha-androstanediol (K(d)=10(-6)M for the AR); while RoDH like 3alpha-HSD (a short-chain dehydrogenase/reductase (SDR)) acts solely as an oxidase to convert 3alpha-androstanediol back to 5alpha-DHT. Our studies suggest that aldo-keto reductase (AKRs) and SDRs function as reductases and oxidases, respectively, to control ligand access to nuclear receptors.