Transcript profiling of the androgen signal in normal prostate, benign prostatic hyperplasia, and prostate cancer

Intrinsic and extrinsic factors causing hyperplasia of the prostate

Prostatic hyperplasia is very common in elderly men and is a typical disease that reduces quality of life. Histologically, hyperplasia of the prostate gland causes obstruction at the bladder outlet, resulting in symptoms such as a weak urine stream. Various factors have been considered to cause histological enlargement of the prostate, but the underlying cause is still unknown. The factors that cause prostate hyperplasia can be broadly classified into intrinsic and extrinsic ones. Extrinsic factors include things that we directly come into contact with such as bacteria and food. On the other hand, intrinsic factors are those that cause changes in functions originally provided in the body due to some cause, including extrinsic factors, such as chronic inflammation and an imbalance of sex hormones. A large number of reports have been made to date regarding the etiology of prostatic hyperplasia, although they have not yet clarified the fundamental cause(s). The various factors currently known should be outlined for future research. Should it be possible to prevent this highly prevalent prostatic hyperplasia which is mainly cause of dcreasing quality of life, there is no doubt that it would be a huge contribution to humanity.

Aberrant activated Notch1 promotes prostate enlargement driven by androgen signaling via disrupting mitochondrial function in mouse

The prostate is a vital accessory gonad in the mammalian male reproductive system. With the ever-increasing proportion of the population over 60 years of age worldwide, the incidence of prostate diseases, such as benign prostatic hyperplasia (BPH) and prostate cancer (PCa), is on the rise and is gradually becoming a significant medical problem globally. The notch signaling pathway is essential in regulating prostate early development. However, the potential regulatory mechanism of Notch signaling in prostatic enlargement and hyperplasia remains unclear. In this study, we proved that overactivation of Notch1 signaling in mouse prostatic epithelial cells (OEx) led to prostatic enlargement via enhancing proliferation and inhibiting apoptosis of prostatic epithelial cells. Further study showed that N1ICD/RBPJ directly up-regulated the androgen receptor (AR) and enhanced prostatic sensitivity to androgens. Hyper-proliferation was not found in orchidectomized OEx mice without androgen supply but was observed after Dihydrotestosterone (DHT) supplementation. Our data showed that the number of mitochondrion in prostatic epithelial cells of OEx mice was increased, but the mitochondrial function was impaired, and the essential activity of the mitochondrial respiratory electron transport chain was significantly weakened. Disordered mitochondrial number and metabolic function further resulted in excessive accumulation of reactive oxygen species (ROS). Importantly, anti-oxidant N-Acetyl-L-Cysteine (NAC) therapy could alleviate prostatic hyperplasia caused by the over-activation of Notch1 signaling. Furthermore, we observed the incremental Notch signaling activity in progenitor-like club cells in the scRNA-seq data set of human BPH patients. Moreover, the increased number of TROP2+ progenitors and Club cells was also confirmed in our OEx mice. In conclusion, our study revealed that over-activated Notch1 signaling induces prostatic enlargement by increasing androgen receptor sensitivity, disrupting cellular mitochondrial metabolism, increasing ROS, and a higher number of progenitor cells, all of which can be effectively rescued by NAC treatment.

Inhibiting CBP Decreases AR Expression and Inhibits Proliferation in Benign Prostate Epithelial Cells

(1) Background: CREB-binding protein (CBP) is a key transcriptional coactivator of androgen receptors (AR). We conducted this study to investigate the effects of CBP on AR expression and proliferation in benign prostatic hyperplasia (BPH) prostate epithelial cells. (2) Methods: By analyzing a published data set, we found that CBP was closely related to the gene expression of AR in prostate cells. We enrolled 20 BPH patients who underwent transurethral resection of the prostate (TURP) in Peking University First Hospital in 2022, and analyzed the expressions of CBP and AR in BPH prostate tissues. Then, we used ICG-001 and shRNA to inhibit CBP in prostate epithelial cells (BPH-1 cells and RWPE-1 cells), and conducted immunofluorescence, cell viability assay, flow cytometry analysis, and Western blot to analyze the effects of CBP on AR expression and proliferation in prostate epithelial cells. We also studied the interaction between CBP and AR through a co-immunoprecipitation assay. (3) Results: CBP is consistent with AR in expression intensity in prostate tissues. Inhibiting CBP decreases AR expression, and induces proliferation inhibition, apoptosis, and cell cycle arrest in BPH prostate epithelial cells. The co-immunoprecipitation assay showed that CBP binds with AR to form transcription complexes in prostate epithelial cells. (4) Conclusions: Inhibiting CBP decreases AR expression and inhibits proliferation in benign prostate epithelial cells. CBP may be a potential target to affect AR expression and the proliferation of prostate epithelial cells in BPH.

AKR1C3 Converts Castrate and Post-Abiraterone DHEA-S into Testosterone to Stimulate Growth of Prostate Cancer Cells via 5-Androstene-3β,17β-Diol

Androgen receptor signaling inhibitors (ARSI) are used to treat castration-resistant prostate cancer (CRPC) to stop a resurgence of androgen receptor (AR) signaling. Despite early success, patients on ARSIs eventually relapse, develop drug resistance, and succumb to the disease. Resistance may occur through intratumoral steroidogenesis mediated by upregulation of aldo-keto reductase family 1C member 3 (AKR1C3). Patients treated with leuprolide (castrate) and those treated with leuprolide plus abiraterone (post-Abi) harbor a reservoir of DHEA-S which could fuel testosterone (T) biosynthesis via AKR1C3 to cause a resurgence of prostate cancer cell growth. We demonstrate that concentrations of DHEA-S found in castrate and post-Abi patients are (i) converted to T in an AKR1C3-dependent manner in prostate cancer cells, and (ii) in amounts sufficient to stimulate AKR1C3-dependent cell growth. We observed this in primary and metastatic prostate cancer cell lines, CWR22PC and DuCaP, respectively. Androgen measurements were made by stable isotope dilution LC-MS/MS. We demonstrate AKR1C3 dependence using stable short hairpin RNA knockdown and pharmacologic inhibitors. We also demonstrate that free DHEA is reduced to 5-androstene-3β,17β-diol (5-Adiol) by AKR1C3 and that this is a major metabolite, suggesting that in our cell lines 5-Adiol is a predominant precursor of T. We have identified a mechanism of ARSI resistance common to both primary and metastatic cell lines that is dependent on the conversion of DHEA to 5-Adiol on route to T catalyzed by AKR1C3.

SIGNIFICANCE

We show that reservoirs of DHEA-S that remain after ARSI treatment are converted into T in primary and metastatic prostate cancer cells in amounts sufficient to stimulate cell growth. Pharmacologic and genetic approaches demonstrate that AKR1C3 is required for these effects. Furthermore, the route to T proceeds through 5-Adiol. We propose that this is a mechanism of ARSI drug resistance.

A Novel Insight into the Immune-Related Interaction of Inflammatory Cytokines in Benign Prostatic Hyperplasia

Benign prostatic hyperplasia (BPH) is a common male condition that impacts many men's quality of life by generating lower urinary tract symptoms (LUTS). In recent years, inflammation has become very common in the prostate, and BPH with inflammation has a higher International Prostate Symptom Score (IPSS) score and an enlarged prostate. Chronic inflammation leads to tissue damage and the release of pro-inflammatory cytokines, which play an important role in the pathogenesis of BPH. We will focus on current advancements in pro-inflammatory cytokines in BPH, as well as the future of pro-inflammatory cytokine research.

Conversion of Classical and 11-Oxygenated Androgens by Insulin-Induced AKR1C3 in a Model of Human PCOS Adipocytes

Polycystic ovary syndrome (PCOS) is the most prevalent endocrinopathy in women. A common symptom of PCOS is hyperandrogenism (AE); however, the source of these androgens is uncertain. Aldo-keto reductase family 1 member C3 (AKR1C3) catalyzes the formation of testosterone (T) and 5α-dihydrotestosterone (DHT) in peripheral tissues, which activate the androgen receptor (AR). AKR1C3 is induced by insulin in adipocytes and may be central in driving the AE in PCOS. We elucidated the conversion of both classical and 11-oxygenated androgens to potent androgens in a model of PCOS adipocytes. Using high-performance liquid chromatography (HPLC) discontinuous kinetic assays to measure product formation by recombinant AKR1C3, we found that the conversion of 11-keto-Δ4-androstene-3,17-dione (11K-4AD) to 11-ketotestosterone (11K-T) and 11-keto-5α-androstane-3,17-dione (11K-5AD) to 11-keto-5α-dihydrotestosterone (11K-DHT) were superior to the formation of T and DHT. We utilized a stable isotope dilution liquid chromatography high resolution mass spectrometric (SID-LC-HRMS) assay for the quantification of both classical and 11-oxygenated androgens in differentiated Simpson-Golabi-Behmel syndrome adipocytes in which AKR1C3 was induced by insulin. Adipocytes were treated with adrenal derived 11β-hydroxy-Δ4-androstene-3,17-dione (11β-OH-4AD), 11K-4AD, or Δ4-androstene-3,17-dione (4AD). The conversion of 11β-OH-4AD and 11K-4AD to 11K-T required AKR1C3. We also found that once 11K-T is formed, it is inactivated to 11β-hydroxy-testosterone (11β-OH-T) by 11β-hydroxysteroid dehydrogenase type 1 (HSD11B1). Our data reveal a unique role for HSD11B1 in protecting the AR from AE. We conclude that the 11-oxygenated androgens formed in adipocytes may contribute to the hyperandrogenic profile of PCOS women and that AKR1C3 is a potential therapeutic target to mitigate the AE of PCOS.

AKR1C1/2 inhibition by MPA sensitizes platinum resistant ovarian cancer towards carboplatin

In recurrent epithelial ovarian cancer (EOC) most patients develop platinum-resistance. On molecular level the NRF2 pathway, a cellular defense mechanism against reactive oxygen species, is induced. In this study, we investigate AKR1C1/2, target of NRF2, in a well-established EOC collective by immunohistochemistry and in a panel of ovarian cancer cell lines including platinum-resistant clones. The therapeutic effect of carboplatin and MPA as monotherapy or in combination was assessed by functional assays, using OV90 and OV90cp cells. Molecular mechanisms of action of MPA were investigated by NRF2 silencing and AKR activity measurements. Immunohistochemical analysis revealed that AKR1C1/2 is a key player in the development of chemoresistance and an independent indicator for short PFS (23.5 vs. 49.6 months, p = 0.013). Inhibition of AKR1C1/2 by MPA led to a concentration- and time-dependent decline of OV90 viability and to an increased response to CP in vitro. By NRF2 silencing, however, the effects of MPA treatment were reduced. Concludingly, our data suggest that a combination therapy of carboplatin and MPA might be a promising therapeutic approach to increase response rates of EOC patients, which should be explored in clinical context.

Is COVID-19 a risk factor for progression of benign prostatic hyperplasia and exacerbation of its related symptoms?: a systematic review

BACKGROUND

To explore the potential mechanisms of SARS-CoV-2 in targeting the prostate gland, leading to exacerbation of benign prostatic hyperplasia (BPH) symptoms and greater risks of BPH complications such as acute urinary retention.

METHODS

A categorized and comprehensive search in the literature has been conducted by 10 April 2021 using international databases including PubMed, Embase, Web of Science, Scopus, and Cochrane Library in line with the PRISMA guidelines recommendations. PICO strategy was used to formulate the research question. The following terms were used: urology, COVID-19, coronavirus, BPH, inflammation, androgen receptors, LUTS, IPSS, PSA, and SARS-CoV-2 or a combination of them. Studies with irrelevant purposes and duplicates were excluded. The selected studies were performed on humans and published in English.

RESULTS

The research revealed 89 articles. After title screening and considering exclusion criteria, 52 papers were included for the systematic review. BPH is a common condition affecting older men. SARS-CoV-2 infects the host cell by binding to angiotensin converting enzyme 2 (ACE2). A hyperactivated RAS system during infection with SARS-CoV-2 may lead to activation of pro-inflammatory pathways and increased cytokine release. Thus, this virus can lead to exacerbation of lower urinary tract symptoms (LUTS) and trigger inflammatory processes in the prostate gland. Since androgen receptors (AR) play an important role in the BPH pathophysiology and infection with SARS-CoV-2 may be androgen-mediated, BPH progression and its related symptoms can be a complication of COVID-19 through AR involvement and metabolic disturbances.

CONCLUSIONS

Based on the current findings, SARS-CoV-2 can possibly damage the prostate and worsen BPH and its related LUTS through ACE2 signaling, AR-related mechanisms, inflammation, and metabolic derangement. We encourage future studies to investigate the possible role of COVID-19 in the progression of BPH-related LUTS and examine the prostatic status in susceptible patients with relevant available questionnaires (e.g., IPSS) and serum biomarkers (e.g., PSA).

Overview of human 20 alpha-hydroxysteroid dehydrogenase (AKR1C1): Functions, regulation, and structural insights of inhibitors

Human aldo-keto reductase family 1C1 (AKR1C1) is an important enzyme involved in human hormone metabolism, which is mainly responsible for the metabolism of progesterone in the human body. AKR1C1 is highly expressed and has an important relationship with the occurrence and development of various diseases, especially some cancers related to hormone metabolism. Nowadays, many inhibitors against AKR1C1 have been discovered, including some synthetic compounds and natural products, which have certain inhibitory activity against AKR1C1 at the target level. Here we briefly reviewed the physiological and pathological functions of AKR1C1 and the relationship with the disease, and then summarized the development of AKR1C1 inhibitors, elucidated the interaction between inhibitors and AKR1C1 through molecular docking results and existing co-crystal structures. Finally, we discussed the design ideals of selective AKR1C1 inhibitors from the perspective of AKR1C1 structure, discussed the prospects of AKR1C1 in the treatment of human diseases in terms of biomarkers, pre-receptor regulation and single nucleotide polymorphisms, aiming to provide new ideas for drug research targeting AKR1C1.

The role of the androgen receptor in prostate development and benign prostatic hyperplasia: A review

Benign prostatic hyperplasia (BPH) is a benign enlargement of the prostate in which incidence increases linearly with age, beginning at about 50 years old. BPH is a significant source of morbidity in aging men by causing lower urinary tract symptoms and acute urinary retention. Unfortunately, the etiology of BPH incidence and progression is not clear. This review highlights the role of the androgen receptor (AR) in prostate development and the evidence for its involvement in BPH. The AR is essential for normal prostate development, and individuals with defective AR signaling, such as after castration, do not experience prostate enlargement with age. Furthermore, decreasing dihydrotestosterone availability through therapeutic targeting with 5α-reductase inhibitors diminishes AR activity and results in reduced prostate size and symptoms in some BPH patients. While there is some evidence that AR expression is elevated in certain cellular compartments, how exactly AR is involved in BPH progression has yet to be elucidated. It is possible that AR signaling within stromal cells alters intercellular signaling and a "reawakening" of the embryonic mesenchyme, loss of epithelial AR leads to changes in paracrine signaling interactions, and/or chronic inflammation aids in stromal or epithelial proliferation evident in BPH. Unfortunately, a subset of patients fails to respond to current medical approaches, forcing surgical treatment even though age or associated co-morbidities make surgery less attractive. Fundamentally, new therapeutic approaches to treat BPH are not currently forthcoming, so a more complete molecular understanding of BPH etiology is necessary to identify new treatment options.

The 11β-hydroxyandrostenedione pathway and C11-oxy C21 backdoor pathway are active in benign prostatic hyperplasia yielding 11keto-testosterone and 11keto-progesterone

In clinical approaches to benign prostatic hyperplasia (BPH) and prostate cancer (PCa), steroidogenesis or the disruption thereof is the main thrust in treatments restricting active androgen production. Extensive studies have been undertaken focusing on testosterone and dihydrotestosterone (DHT). However, the adrenal C11-oxy C₁₉ steroid, 11β-hydroxyandrostenedione (11OHA4), also contributes to the active androgen pool in the prostate microenvironment, and while it has been shown to impact castration resistant prostate cancer, the C11-oxy C₁₉ steroids together with the C11-oxy C₂₁ steroids have not been studied in BPH. The study firstly investigated the metabolism of these adrenal steroids in the BPH-1 model. Comprehensive profiles identified 11keto-testosterone as the predominant active androgen in the metabolism of the C11-oxy C₁₉ steroids, and we identified, for the first time, 11β-hydroxy-5α-androstane-3α,17β-diol, a novel steroid in the 11OHA4-pathway. Analysis of the inactivation and reactivation of the metabolites showed that DHT is more readily inactivated than 11keto-dihydrotestosterone (11KDHT). The conversion of 11β-hydroxyprogesterone (11βOHPROG) yielded 11keto-progesterone (11KPROG), while the latter yielded 11keto-dihydroprogesterone (11KDHPROG). BPH tissue analysis identified high levels of 11β-hydroxyandrosterone (4-14 ng/g) and 11keto-androsterone (9-160 ng/g), together with androstenedione (A4; ∼7.5 ng/g). The major C11-oxy C₂₁ steroids detected were 11βOHPROG (∼46 ng/g), 11KPROG (∼130 ng/g) as well as 11KDHPROG (∼282 ng/g). While circulatory 11βOHPROG was detected below the limit of quantification, 11KPROG and 11KDHPROG were detected at 6 and 8.5 nmol/L, respectively. Glucuronide derivatives of both 11KPROG and pregnanetriol were also detected. 11OHA4 was the major free androgen in circulation at 85.9 nmol/L, ±12-fold higher than A4, together with 5α-androstane-3α,17β-diol quantified at 69.3 nmol/L. Circulatory C11-oxy C₁₉ steroids levels were also significantly higher (8-fold) than the C11-oxy C₂₁ steroid levels, while the former were similar to the C₁₉ steroid levels, in contrast to levels in PCa. The study highlights the contribution of adrenal C11-oxy steroids to the androgen pool in BPH underscoring their limited reactivation and elimination, and significant inter-individual variations regarding steroid levels and conjugation. Targeted steroid metabolome analysis is critical to understanding prostate steroidogenesis and disease progression, and analysis of circulatory C11-oxy C₁₉ and C11-oxy C₂₁ steroids, together with intraprostatic levels, add to our current understanding of BPH.

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.

Genetic and molecular determinants of prostate cancer among Iranian patients: An update

Prostate cancer (PCa) is one of the most common age-related cancers among men. Various environmental and genetic factors are involved in the development and progression of PCa. In most cases, the primary symptoms of disease are not severe. Therefore, it is common for patients to be referred with severe clinical manifestations at advanced stages of disease. Since this malignancy is age related and Iran will face a significant increase in the number of seniors, it is expected that the prevalence of PCa among Iranian men will rise. PCa progression has been observed to be associated with genetic and ethnic factors. It may therefore be clinically useful to determine a panel of genetic markers, in addition to routine diagnostic methods, to detect tumors in the early stages. In the present review, we have summarized the reported genetic markers in PCa Iranian patients to pave the way for the determination of an ethnic specific genetic marker panel for the early detection of PCa. To understand the genetic and molecular biology of PCa among Iranians, we have categorized these genetic markers based on their cellular functions.

Induction of the Antioxidant Response by the Transcription Factor NRF2 Increases Bioactivation of the Mutagenic Air Pollutant 3-Nitrobenzanthrone in Human Lung Cells

3-Nitrobenzanthrone (3-NBA) is a suspected human carcinogen present in diesel exhaust. It requires metabolic activation via nitroreduction in order to form DNA adducts and promote mutagenesis. We have determined that human aldo-keto reductases (AKR1C1-1C3) and NAD(P)H:quinone oxidoreductase 1 (NQO1) contribute equally to the nitroreduction of 3-NBA in lung epithelial cell lines and collectively represent 50% of the nitroreductase activity. The genes encoding these enzymes are induced by the transcription factor NF-E2 p45-related factor 2 (NRF2), which raises the possibility that NRF2 activation exacerbates 3-NBA toxification. Since A549 cells possess constitutively active NRF2, we examined the effect of heterozygous (NRF2-Het) and homozygous NRF2 knockout (NRF2-KO) by CRISPR-Cas9 gene editing on the activation of 3-NBA. To evaluate whether NRF2-mediated gene induction increases 3-NBA activation, we examined the effects of NRF2 activators in immortalized human bronchial epithelial cells (HBEC3-KT). Changes in AKR1C1-1C3 and NQO1 expression by NRF2 knockout or use of NRF2 activators were confirmed by qPCR, immunoblots, and enzyme activity assays. We observed decreases in 3-NBA activation in the A549 NRF2 KO cell lines (53% reduction in A549 NRF2-Het cells and 82% reduction in A549 NRF2-KO cells) and 40-60% increases in 3-NBA bioactivation due to NRF2 activators in HBEC3-KT cells. Together, our data suggest that activation of the transcription factor NRF2 exacerbates carcinogen metabolism following exposure to diesel exhaust which may lead to an increase in 3-NBA-derived DNA adducts.

Alternative pathway androgen biosynthesis and human fetal female virilization

In the classic androgen biosynthesis pathway, testosterone is converted to 5α-dihydrotestosterone, a step crucially required for normal male genital virilization. Congenital adrenal hyperplasia (CAH) due to P450 oxidoreductase deficiency (PORD) is an inborn disorder that disrupts classic androgen biosynthesis. However, some affected girls present with severe genital virilization at birth. We hypothesized that this is explained by a prenatally active, alternative biosynthesis pathway to 5α-dihydrotestosterone. We show that adrenals and genital skin cooperate to produce androgens via the alternative pathway during the major period of human sexual differentiation and that neonates with PORD still produce alternative pathway androgens during the first weeks of life. This indicates that alternative pathway androgen biosynthesis drives prenatal virilization in CAH due to PORD.

Androgen biosynthesis in the human fetus proceeds through the adrenal sex steroid precursor dehydroepiandrosterone, which is converted to testosterone in the gonads, followed by further activation to 5α-dihydrotestosterone in genital skin, thereby facilitating male external genital differentiation. Congenital adrenal hyperplasia due to P450 oxidoreductase deficiency results in disrupted dehydroepiandrosterone biosynthesis, explaining undervirilization in affected boys. However, many affected girls are born virilized, despite low circulating androgens. We hypothesized that this is due to a prenatally active, alternative androgen biosynthesis pathway from 17α-hydroxyprogesterone to 5α-dihydrotestosterone, which bypasses dehydroepiandrosterone and testosterone, with increased activity in congenital adrenal hyperplasia variants associated with 17α-hydroxyprogesterone accumulation. Here we employ explant cultures of human fetal organs (adrenals, gonads, genital skin) from the major period of sexual differentiation and show that alternative pathway androgen biosynthesis is active in the fetus, as assessed by liquid chromatography–tandem mass spectrometry. We found androgen receptor expression in male and female genital skin using immunohistochemistry and demonstrated that both 5α-dihydrotestosterone and adrenal explant culture supernatant induce nuclear translocation of the androgen receptor in female genital skin primary cultures. Analyzing urinary steroid excretion by gas chromatography–mass spectrometry, we show that neonates with P450 oxidoreductase deficiency produce androgens through the alternative androgen pathway during the first weeks of life. We provide quantitative in vitro evidence that the corresponding P450 oxidoreductase mutations predominantly support alternative pathway androgen biosynthesis. These results indicate a key role of alternative pathway androgen biosynthesis in the prenatal virilization of girls affected by congenital adrenal hyperplasia due to P450 oxidoreductase deficiency.

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.

Genetic variations in UGT2B28, UGT2B17, UGT2B15 genes and the risk of prostate cancer: A case-control study

Glucuronidation is a major pathway for elimination of exogenous and endogenous compounds such as environmental carcinogens and androgens from the body. This biochemical pathway is mediated by enzymes called uridine diphosphoglucuronosyltransferases (UGTs). Null (del/del) genes polymorphisms in UGT2B17, and UGT2B28 and D85Y single-nucleotide polymorphism (SNP) of UGT2B15 have been reported to increase the risk of prostate cancer. The goal of this study was to determine the association of mentioned genetic variants with the risk of prostate cancer. We investigated the copy number variations (CNVs) of UGT2B17 and UGT2B28 loci and the association between rs1902023 polymorphism of UGT2B15 gene in 360 subjects consisted of 120 healthy controls, 120 prostate cancer (PC) patients and 120 benign prostatic hyperplasia (BPH) patients. No association was detected for the mentioned polymorphisms and the risk of PC. However, a significant association was detected between UGT2B17 copy number variation and BPH risk (OR=2.189; 95% CI, 1.303-3.675; p=0.003). Furthermore, we observed that the D85Y polymorphism increases the risk of BPH when analyzed in combination with the copy number variation of UGT2B17 gene (OR=0.135; 95% CI, 0.036-0.512; p=0.003). Our findings suggest that the D85Y polymorphism of UGT2B15 and CNVs in UGT2B28 and UGT2B17 genes is not associated with prostate cancer risk in Iranian patients. To our knowledge, this is the first report that implicates the role of CNV of UGT2B17 gene in BPH.

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.

Knockdown of AKR1C3 exposes a potential epigenetic susceptibility in prostate cancer cells

BACKGROUND

The aldo-keto reductase 1C3 (AKR1C3) has been heavily implicated in the propagation of prostate malignancy. AKR1C3 protein is elevated within prostate cancer tissue, it contributes to the formation of androgens and downstream stimulation of the androgen receptor (AR). Elevated expression of AKR1C3 is also reported in acute myeloid leukemia but the target nuclear receptors have been identified as members of the peroxisome-proliferator activated receptor (PPARs) subfamily. Thus, AKR1C3 cancer biology is likely to be tissue dependent and hormonally linked to the availability of ligands for both the steroidogenic and non-steroidogenic nuclear receptors.

METHODS

In the current study we investigated the potential for AKR1C3 to regulate the availability of prostaglandin-derived ligands for PPARg mainly, prostaglandin J2 (PGJ2). Using prostate cancer cell lines with stably reduced AKR1C3 levels we examined the impact of AKR1C3 upon proliferation mediated by PPAR ligands.

RESULTS

These studies revealed knockdown of AKR1C3 had no effect upon the sensitivity of androgen receptor independent prostate cancer cells towards PPAR ligands. However, the reduction of levels of AKR1C3 was accompanied by a significantly reduced mRNA expression of a range of HDACs, transcriptional co-regulators, and increased sensitivity towards SAHA, a clinically approved histone deacetylase inhibitor.

CONCLUSIONS

These results suggest a hitherto unidentified link between AKR1C3 levels and the epigenetic status in prostate cancer cells. This raises an interesting possibility of a novel rational to target AKR1C3, the utilization of AKRIC3 selective inhibitors in combination with HDAC inhibition as part of novel epigenetic therapies in androgen deprivation therapy recurrent prostate cancer.

Promiscuity and diversity in 3-ketosteroid reductases

Many steroid hormones contain a Δ(4)-3-ketosteroid functionality that undergoes sequential reduction by 5α- or 5β- steroid reductases to produce 5α- or 5β-dihydrosteroids; and a subsequent 3-keto-reduction to produce a series of isomeric tetrahydrosteroids. Apart from steroid 5α-reductase all the remaining enzymes involved in the two step reduction process in humans belong to the aldo-keto reductase (AKR) superfamily. The enzymes involved in 3-ketosteroid reduction are AKR1C1-AKR1C4. These enzymes are promiscuous and also catalyze 20-keto- and 17-keto-steroid reduction. Interest in these reactions exist since they regulate steroid hormone metabolism in the liver, and in steroid target tissues, they may regulate steroid hormone receptor occupancy. In addition many of the dihydrosteroids are not biologically inert. The same enzymes are also involved in the metabolism of synthetic steroids e.g., hormone replacement therapeutics, contraceptive agents and inhaled glucocorticoids, and may regulate drug efficacy at their cognate receptors. This article reviews these reactions and the structural basis for substrate diversity in AKR1C1-AKR1C4, ketosteroid reductases. This article is part of a Special Issue entitled 'Steroid/Sterol signaling'.

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.

Androgen biosynthesis in castration-resistant prostate cancer

Prostate cancer is the second leading cause of death in adult males in the USA. Recent advances have revealed that the fatal form of this cancer, known as castration-resistant prostate cancer (CRPC), remains hormonally driven despite castrate levels of circulating androgens. CRPC arises as the tumor undergoes adaptation to low levels of androgens by either synthesizing its own androgens (intratumoral androgens) or altering the androgen receptor (AR). This article reviews the major routes to testosterone and dihydrotestosterone synthesis in CRPC cells and examines the enzyme targets and progress in the development of isoform-specific inhibitors that could block intratumoral androgen biosynthesis. Because redundancy exists in these pathways, it is likely that inhibition of a single pathway will lead to upregulation of another so that drug resistance would be anticipated. Drugs that target multiple pathways or bifunctional agents that block intratumoral androgen biosynthesis and antagonize the AR offer the most promise. Optimal use of enzyme inhibitors or AR antagonists to ensure maximal benefits to CRPC patients will also require application of precision molecular medicine to determine whether a tumor in a particular patient will be responsive to these treatments either alone or in combination.

Molecular effects of bioactive fraction of Curcuma mangga (DLBS4847) as a downregulator of 5α-reductase activity pathways in prostatic epithelial cells

DLBS4847 is a standardized bioactive fraction of Curcuma mangga. In this study, we used prostate cancer (PC)-3 as the cell line to study the effects of DLBS4847 on prostatic cell viability, as well as related molecular changes associated with the decreased cell number. The observation revealed that DLBS4847 inhibited the growth of PC3 cells through downregulation of the 5α-reductase (5AR) pathway. At the transcription level, 5AR1 and androgen-receptor gene expressions were downregulated in a dose-dependent manner. Furthermore, 5AR-1 and dihydrotestosterone expression were also downregulated at the protein level. A microarray study was also performed to see the effects of DLBS4847 on differential gene expressions in prostate cancer 3 cells. Among others, DLBS4847 downregulated genes related to prostate growth and hypertrophy. Our results suggested that DLBS4847 could potentially become an alternative treatment for prostate disorders, such as benign prostatic hyperplasia. In this regard, DLBS4847 exerts its growth inhibition partially through downregulation of the 5AR pathway.

Role of aldo-keto reductase family 1 (AKR1) enzymes in human steroid metabolism

Human aldo-keto reductases AKR1C1-AKR1C4 and AKR1D1 play essential roles in the metabolism of all steroid hormones, the biosynthesis of neurosteroids and bile acids, the metabolism of conjugated steroids, and synthetic therapeutic steroids. These enzymes catalyze NADPH dependent reductions at the C3, C5, C17 and C20 positions on the steroid nucleus and side-chain. AKR1C1-AKR1C4 act as 3-keto, 17-keto and 20-ketosteroid reductases to varying extents, while AKR1D1 acts as the sole Δ(4)-3-ketosteroid-5β-reductase (steroid 5β-reductase) in humans. AKR1 enzymes control the concentrations of active ligands for nuclear receptors and control their ligand occupancy and trans-activation, they also regulate the amount of neurosteroids that can modulate the activity of GABAA and NMDA receptors. As such they are involved in the pre-receptor regulation of nuclear and membrane bound receptors. Altered expression of individual AKR1C genes is related to development of prostate, breast, and endometrial cancer. Mutations in AKR1C1 and AKR1C4 are responsible for sexual development dysgenesis and mutations in AKR1D1 are causative in bile-acid deficiency.

Modulators of estrogen receptor inhibit proliferation and migration of prostate cancer cells

In the initial stages, human prostate cancer (PC) is an androgen-sensitive disease, which can be pharmacologically controlled by androgen blockade. This therapy often induces selection of androgen-independent PC cells with increased invasiveness. We recently demonstrated, both in cells and mice, that a testosterone metabolite locally synthetized in prostate, the 5α-androstane-3β, 17β-diol (3β-Adiol), inhibits PC cell proliferation, migration and invasion, acting as an anti-proliferative/anti-metastatic agent. 3β-Adiol is unable to bind androgen receptor (AR), but exerts its protection against PC by specifically interacting with estrogen receptor beta (ERβ). Because of its potential retro-conversion to androgenic steroids, 3β-Adiol cannot be used "in vivo", thus, the aims of this study were to investigate the capability of four ligands of ERβ (raloxifen, tamoxifen, genistein and curcumin) to counteract PC progression by mimicking the 3β-Adiol activity. Our results demonstrated that raloxifen, tamoxifen, genistein and curcumin decreased DU145 and PC3 cell proliferation in a dose-dependent manner; in addition, all four compounds significantly decreased the detachment of cells seeded on laminin or fibronectin. Moreover, raloxifen, tamoxifen, genistein and curcumin-treated DU145 and PC3 cells showed a significant decrease in cell migration. Notably, all these effects were reversed by the anti-estrogen, ICI 182,780, suggesting that their actions are mediated by the estrogenic pathway, via the ERβ, the only isoform present in these PCs. In conclusion, these data demonstrate that by selectively activating the ERβ, raloxifen, tamoxifen, genistein and curcumin inhibit human PC cells proliferation and migration favoring cell adesion. These synthetic and natural modulators of ER action may exert a potent protective activity against the progression of PC even in its androgen-independent status.

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.

Testosterone effect on the expression of genes that mediate testosterone metabolism and genes that mediate the effect of those metabolites on the prostate

AIMS

The aim of this study was to investigate the effect of testosterone treatment on the proliferation index and the mRNA expression levels of 5α-reductase, CYP7B1, androgen receptor (AR), and estrogen receptor β (ΕRβ) in the canine prostate.

MAIN METHODS

Immature dogs were treated with testosterone for one month, after which prostate gland growth was assessed by comparing the proliferation index in prostates from testosterone-treated dogs with that of untreated control dogs. The relative mRNA expression levels of the aforementioned genes in the prostate glands of testosterone-treated and untreated dogs were determined by real time PCR.

KEY FINDINGS

Testosterone treatment induced a highly significant reduction in proliferation index in prostate gland. This inhibition of prostate gland growth was associated with differential mRNA expression of 5α-reductase, CYP7B1, AR, and ΕRβ by the prostate gland of testosterone-treated dogs, as compared to that of untreated dogs. While the expression levels of 5α-reductase and CYP7B1 mRNA were significantly down-regulated by testosterone treatment, the expression level of ER-β mRNA was highly up-regulated. In contrast, AR mRNA expression was not significantly altered.

SIGNIFICANCE

Prostate gland proliferation appeared to be associated with the expression levels of genes that encode proteins that control intra-prostatic levels of testosterone metabolites and their respective receptors. Testosterone treatment may regulate gene expression in the prostate to generate a phenotype that suppresses growth-promoting signaling through AR and enhances anti-proliferative signaling through ERβ. Therefore, targeting disturbances of this genetic machinery in benign prostate hyperplasia and prostate cancer is of a therapeutic potential.

Estrogen receptor β and 17β-hydroxysteroid dehydrogenase type 6, a growth regulatory pathway that is lost in prostate cancer

Estrogen receptor β (ERβ) is activated in the prostate by 5α-androstane-3β,17β-diol (3β-Adiol) where it exerts antiproliferative activity. The proliferative action of the androgen receptor is activated by 5α-dihydrotestosterone (DHT). Thus, prostate growth is governed by the balance between androgen receptor and ERβ activation. 3β-Adiol is a high-affinity ligand and agonist of ERβ and is derived from DHT by 3-keto reductase/3β-hydroxysteroid dehydrogenase enzymes. Here, we demonstrate that, when it is expressed in living cells containing an estrogen response element-luciferase reporter, 17β-hydroxysteroid dehydrogenase type 6 (17βHSD6) converts the androgen DHT to the estrogen 3β-Adiol, and this leads to activation of the ERβ reporter. This conversion of DHT occurs at concentrations that are in the physiological range of this hormone in the prostate. Immunohistochemical analysis revealed that 17βHSD6 is expressed in ERβ-positive epithelial cells of the human prostate and that, in prostate cancers of Gleason grade higher than 3, both ERβ and 17βHSD6 are undetectable. Both proteins were present in benign prostatic hyperplasia samples. These observations reveal that formation of 3β-Adiol via 17βHSD6 from DHT is an important growth regulatory pathway that is lost in prostate cancer.

Intratumoral androgen biosynthesis in prostate cancer pathogenesis and response to therapy

The majority of prostate cancers (PCa) express high levels of androgen receptor (AR) and are dependent for their growth on testosterone produced by the testes, which is reduced in the prostate to the higher affinity ligand 5α-dihydrotestosterone (DHT). PCa growth can be suppressed by androgen deprivation therapy, which involves removal of testicular androgens (surgical or medical castration) or treatment with an AR antagonist (or a combination of both), but patients invariably relapse with tumors that have been termed castration recurrent/resistant PCa (CRPC). Importantly, AR transcriptional activity becomes reactivated at this CRPC stage of the disease and remains essential for tumor growth. The objective of this review is to outline one clinically important mechanism contributing to this AR reactivation, which is increased intratumoral synthesis of testosterone and DHT from weak androgens produced by the adrenal glands and possibly de novo from cholesterol. Early studies showed that a substantial fraction of CRPC patients responded to adrenalectomy or medical suppression of adrenal androgen synthesis using agents such as ketoconazole (CYP17A1 inhibitor), and a recent phase III study of a more potent and selective CYP17A1 inhibitor (abiraterone) has demonstrated an improvement in survival. With the pending FDA approval of abiraterone for CRPC, defining the molecular mechanisms contributing to CYP17A1 inhibitor resistance/relapse and AR reactivation is now critical to build on these advances.

Transforming growth factor β1 increase of hydroxysteroid dehydrogenase proteins is partly suppressed by red clover isoflavones in human primary prostate cancer-derived stromal cells

Transforming growth factor β1 (TGF-β1) increases dehydro-epiandrosterone (DHEA) metabolism to androgens and prostate-specific antigen (PSA) in a prostate tissue model where stromal (6S) cells and epithelial (LAPC-4) cells are cocultured. Red clover (RC) isoflavones inhibits transforming growth factor (TGF)-β-induced androgenicity. Mechanisms controlling those activities were explored. Three hydroxysteroid dehydrogenases (HSDs), 3β-HSD, HSD-17β1 and HSD-17β5 involved in metabolizing DHEA to testosterone (TESTO) were investigated. Individual depletion of HSDs in 6S cells significantly reduced TGF-β1/DHEA-induced PSA in LAPC-4 cells in cocultures. Monomer amounts of 3β-HSD were similar without or with TGF-β1 in both cell types but aggregates of 3β-HSD in 6S cells were much higher than those in LAPC-4 cells and were upregulated by TGFβ in 6S cells. Basal and TGF-β1-treated levels of HSD-17β1 and HSD-17β5 in LAPC-4 cells were significantly lower than in 6S cells, whereas levels of HSD-17β1 but not HSD-17β5 were TGFβ inducible. 6S cell HSD genes expression induced by TGFβ or androgen signaling was insignificant to contribute TGF-β1/DHEA-upregulated protein levels of HSDs. RC decreased TGF-β1- upregulation of aggregates of 3β-HSD but not HSD-17β1. Depletion of TGFβ receptors (TGFβ Rs) reduced TGF-β1/DHEA-upregulated HSDs and TESTO. Immunoprecipitation studies demonstrated that TGF-β1 disrupted associations of TGFβ Rs/HSDs aggregates, whereas RC suppressed the dissociations of aggregates of 3β-HSD but not HSD-17β1 from the receptors. Given that TGFβ Rs are recycled with or without ligand, TGF-β1-induced disassociation of the HSDs from TGFβ Rs may increase stability and activity of the HSDs. These data suggest a pathway connecting overproduction of TGFβ with increased PSA in prostate cancer.

New hormonal therapies for castration-resistant prostate cancer

Continued activation of the androgen receptor (AR) axis despite castration remains a critical force in the development of castration-resistant prostate cancer (CRPC). Therapeutic strategies designed to more effectively ablate tumoral androgen activity are required to improve clinical efficacy and prevent disease progression. Tumor-based alterations in expression and activity of the AR and in steroidogenic pathways mediating ligand generation facilitate the development of CRPC. This article reviews AR and ligand-dependent mechanisms underlying CRPC progression and the status of novel hormonal therapies targeting the AR axis that are currently in clinical and preclinical development.

Intratumoral de novo steroid synthesis activates androgen receptor in castration-resistant prostate cancer and is upregulated by treatment with CYP17A1 inhibitors

Relapse of castration-resistant prostate cancer (CRPC) that occurs after androgen deprivation therapy of primary prostate cancer can be mediated by reactivation of the androgen receptor (AR). One important mechanism mediating this AR reactivation is intratumoral conversion of the weak adrenal androgens DHEA and androstenedione into the AR ligands testosterone and dihydrotestosterone. DHEA and androstenedione are synthesized by the adrenals through the sequential actions of the cytochrome P450 enzymes CYP11A1 and CYP17A1, so that CYP17A1 inhibitors such as abiraterone are effective therapies for CRPC. However, the significance of intratumoral CYP17A1 and de novo androgen synthesis from cholesterol in CRPC, and the mechanisms contributing to CYP17A1 inhibitor resistance/relapse, remain to be determined. We report that AR activity in castration-resistant VCaP tumor xenografts can be restored through CYP17A1-dependent de novo androgen synthesis, and that abiraterone treatment of these xenografts imposes selective pressure for increased intratumoral expression of CYP17A1, thereby generating a mechanism for development of resistance to CYP17A1 inhibitors. Supporting the clinical relevance of this mechanism, we found that intratumoral expression of CYP17A1 was markedly increased in tumor biopsies from CRPC patients after CYP17A1 inhibitor therapy. We further show that CRPC cells expressing a progesterone responsive T877A mutant AR are not CYP17A1 dependent, but that AR activity in these cells is still steroid dependent and mediated by upstream CYP11A1-dependent intraturmoral pregnenolone/progesterone synthesis. Together, our results indicate that CRPCs resistant to CYP17A1 inhibition may remain steroid dependent and therefore responsive to therapies that can further suppress de novo intratumoral steroid synthesis.

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.

Contractility and pacemaker cells in the prostate gland

PURPOSE

We focused on the current opinion on mechanisms generating stromal tone in the prostate gland.

MATERIALS AND METHODS

We selected the guinea pig as the main species for investigation since its prostate has a high proportion of smooth muscle that undergoes age related changes similar in many respects to that in humans. The main techniques that we used were tension recording and electrophysiology.

RESULTS

We previously reported distinct electrical activity and cell types in the prostate, and speculated on their functional roles. We believe that a specialized group of c-kit immunoreactive prostatic interstitial cells that lie between glandular epithelium and smooth muscle stroma have a role similar to that of gastrointestinal interstitial cells of Cajal, generating the pacemaker signal that manifests as slow wave activity and triggers contraction in smooth muscle cells in guinea pig prostates.

CONCLUSIONS

Since changes in muscle tone are involved in the etiology of age dependent prostate specific conditions such as benign prostatic hyperplasia, knowledge of the electrical properties of the various prostatic cell types and their interactions with each other, with nerves and with the hormonal environment, and how these factors change with age is of considerable medical importance.

Modeling single nucleotide polymorphisms in the human AKR1C1 and AKR1C2 genes: implications for functional and genotyping analyses

Enzymes encoded by the AKR1C1 and AKR1C2 genes are responsible for the metabolism of progesterone and 5α-dihydrotestosterone (DHT), respectively. The effect of amino acid substitutions, resulting from single nucleotide polymorphisms (SNPs) in the AKR1C2 gene, on the enzyme kinetics of the AKR1C2 gene product were determined experimentally by Takashi et al. In this paper, we used homology modeling to predict and analyze the structure of AKR1C1 and AKR1C2 genetic variants. The experimental reduction in enzyme activity in the AKR1C2 variants F46Y and L172Q, as determined by Takahashi et al., is predicted to be due to increased instability in cofactor binding, caused by disruptions to the hydrogen bonds between NADP and AKR1C2, resulting from the insertion of polar residues into largely non-polar environments near the site of cofactor binding. Other AKR1C2 variants were shown to involve either conservative substitutions or changes taking place on the surface of the molecule and distant from the active site, confirming the experimental finding of Takahashi et al. that these variants do not result in any statistically significant reduction in enzyme activity. The AKR1C1 R258C variant is predicted to have no effect on enzyme activity for similar reasons. Thus, we provide further insight into the molecular mechanism of the enzyme kinetics of these proteins. Our data also highlight previously reported difficulties with online databases.

The effect of estrogen supplementation on cell proliferation and expression of c-kit positive cells in the rat prostate

BACKGROUND

Benign prostatic hyperplasia (BPH) is associated with the proliferation of prostate tissue and an increase in smooth muscle tone. However, the way in which the hormonal environment affects cell proliferation and prostatic interstitial cells (PIC) responsible for the maintenance of the smooth muscle tone is not clear. The present study investigated the effect of estrogen supplementation on cell proliferation, androgen/estrogen ratio, and expression and/or distribution of PIC.

METHODS

Male Sprague-Dawley rats were anesthetized with isoflurane/oxygen breathing mixture and subcutaneously implanted with silastic capsules. These capsules were either empty or filled with a 10 or 20 mg of crystalline estrogen.

RESULTS

Estrogen exerted a potent effect on ventral prostate weight, which was manifested as a significant decrease between controls and the E(10)- and E(20)-treated rats. Active cell proliferation detected as Ki67-positive nuclei was observed in the stromal and epithelial cells of the ventral prostatic lobes from estrogen-treated rats and controls. Estrogen supplementation caused a significant and dose-dependent increase in prostatic estradiol and 5alpha-dihydrotestosterone (DHT) concentration but the ratios of either DHT/E(2) or E(2)/DHT were not significantly affected. PIC were observed in the region between the fibromuscular stroma and the glandular epithelium in all three experimental groups. E(20)-treated rats showed a higher expression of PIC than controls and E(10)-treated rats.

CONCLUSIONS

The present study provides novel information regarding the synergistic role of estrogens and androgens in the prostate: estrogen may prevent prostatic hyperplasia via mechanisms other than affecting cell proliferation or DHT/estrogen ratio.

A transcriptional signature associated with the onset of benign prostate hyperplasia in a canine model

BACKGROUND

Benign prostatic hyperplasia (BPH) represents the most frequent proliferative abnormality of the human prostate. In spite of the well-characterized architectural development of BPH, little is known about the cellular and molecular events that contribute to it.

METHODS

We have developed an animal model to evaluate the follow-up of hormone-induced BPH and the analysis of the gene expression associated with BPH. Immunohistochemistry on human patient samples validated the BPH-related molecular alterations.

RESULTS

Canine specific Affymetrix microarray analysis performed on sequential biopsies obtained from a beagle dog dynamic model characterized a number of genes altered during the onset of BPH. In addition to the genes involved in calcification, matrix remodeling, detoxification, cell movement, and mucosa protection (MGP, MMP2, TIMP2, ITIH3, GST, MT2A, SULT1A1, FKBP1B, MUC1, STRBP, TFF3), the up-regulation of TGFB3 and CLU indicated a complete adjustment of the transdifferentiation, senescence and apoptosis programs. The up-regulation of Clusterin was validated by RT-qPCR and immunohistochemistry, both in the dog dynamic model and in human samples, further confirming the suitability of the animal model for the study of the molecular alterations associated with BPH.

CONCLUSIONS

Transcriptome analysis performed on a dynamic animal model that accurately mimicked the human clinic, allowed us to characterize a gene expression pattern associated with the onset of BPH.

Non-stereo-selective cytosolic human brain tissue 3-ketosteroid reductase is refractory to inhibition by AKR1C inhibitors

Cerebral 3α-hydroxysteroid dehydrogenase (3α-HSD) activity was suggested to be responsible for the local directed formation of neuroactive 5α,3α-tetrahydrosteroids (5α,3α-THSs) from 5α-dihydrosteroids. We show for the first time that within human brain tissue 5α-dihydroprogesterone and 5α-dihydrotestosterone are converted via non-stereo-selective 3-ketosteroid reductase activity to produce the respective 5α,3α-THSs and 5α,3β-THSs. Apart from this, we prove that within the human temporal lobe and limbic system cytochrome P450c17 and 3β-HSD/Δ(5-4) ketosteroid isomerase are not expressed. Thus, it appears that these brain regions are unable to conduct de novo biosynthesis of Δ(4)-3-ketosteroids from Δ(5)-3β-hydroxysteroids. Consequently, the local formation of THSs will depend on the uptake of circulating Δ(4)-3-ketosteroids such as progesterone and testosterone. 3α- and 3β-HSD activity were (i) equally enriched in the cytosol, (ii) showed equal distribution between cerebral neocortex and subcortical white matter without sex- or age-dependency, (iii) demonstrated a strong and significant positive correlation when comparing 46 different specimens and (iv) exhibited similar sensitivities to different inhibitors of enzyme activity. These findings led to the assumption that cerebral 3-ketosteroid reductase activity might be catalyzed by a single enzyme and is possibly attributed to the expression of a soluble AKR1C aldo-keto reductase. AKR1Cs are known to act as non-stereo-selective 3-ketosteroid reductases; low AKR1C mRNA expression was detected. However, the cerebral 3-ketosteroid reductase was clearly refractory to inhibition by AKR1C inhibitors indicating the expression of a currently unidentified enzyme. Its lack of stereo-selectivity is of physiological significance, since only 5α,3α-THSs enhance the effect of GABA on the GABA(A) receptor, whereas 5α,3β-THSs are antagonists.

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.

Lack of functional and expression homology between human and mouse aldo-keto reductase 1C enzymes: implications for modelling human cancers

Background

Over recent years, enzymes of the aldo-keto reductase (AKR) 1C subfamily have been implicated in the progression of prostate, breast, endometrial and leukemic cancers. This is due to the ability of AKR1C enzymes to modify androgens, estrogens, progesterone and prostaglandins (PGs) in a tissue-specific manner, regulating the activity of nuclear receptors and other downstream effects. Evidence supporting a role for AKR1C enzymes in cancer derives mostly from studies with isolated primary cells from patients or immortalized cell lines. Mice are ideal organisms for in vivo studies, using knock-out or over-expression strains. However, the functional conservation of AKR1C enzymes between human and mice has yet to be described.

Results

In this study, we have characterized and compared the four human (AKR1C1,-1C2, -1C3 and -1C4) and the eight murine (AKR1C6, -1C12, -1C13, -1C14, -1C18, -1C19, -1C20 and -1C21) isoforms in their phylogeny, substrate preference and tissue distribution. We have found divergent evolution between human and murine AKR1C enzymes that was reflected by differing substrate preference. Murine enzymes did not perform the 11β-ketoreduction of prostaglandin (PG) D₂, an activity specific to human AKR1C3 and important in promoting leukemic cell survival. Instead, murine AKR1C6 was able to perform the 9-ketoreduction of PGE₂, an activity absent amongst human isoforms. Nevertheless, reduction of the key steroids androstenedione, 5α-dihydrotestosterone, progesterone and estrone was found in murine isoforms. However, unlike humans, no AKR1C isoforms were detected in murine prostate, testes, uterus and haemopoietic progenitors.

Conclusions

This study exposes significant lack of phylogenetic and functional homology between human and murine AKR1C enzymes. Therefore, we conclude that mice are not suitable to model the role of AKR1C in human cancers and leukemia.

The expression of androgen-responsive genes is up-regulated in the epithelia of benign prostatic hyperplasia

BACKGROUND

Benign prostatic hyperplasia (BPH) is one of the most common diseases among aging men in the United States. In addition to aging, the presence of androgens is another major risk factor in BPH development. However, whether androgen signaling is altered in BPH remains unclear. To determine androgen signaling in BPH, we characterized the expression of four different androgen-responsive genes, Eaf2/U19, ELL2, FKBP5, and PSA, in BPH and adjacent normal glandular epithelial cells.

METHODS

A set of 17 BPH specimens were resected from patients over 60 years of age with clinical symptoms of BPH. Laser-capture microdissection (LCM) was used to isolate glandular epithelial cells from BPH areas and adjacent normal areas, separately. LCM isolated cells from individual specimens were lysed and RNA isolation, reverse transcription, and real-time PCR were performed using CellsDirect One-Step qRT-PCR Kit (Invitrogen, Carlsbad, CA).

RESULTS

All of the assayed genes displayed increased expression, from approximately 2- to approximately 6-fold, in BPH as compared to the adjacent normal epithelial cells. We also generated a composite androgen response index based on the expression levels of the four genes, which provides a reliable readout for overall androgen action. Our study showed that the composite androgen response index in BPH is approximately 4-fold as compared to that in the adjacent normal tissues.

CONCLUSIONS

Androgen signaling is significantly elevated in BPH relative to the adjacent normal prostate. Understanding the mechanisms causing elevated androgen signaling may lead to novel approaches for prevention and/or treatment of BPH.

Developmental evaluation of aldo-keto reductase 1C3 expression in the cryptorchid testis

OBJECTIVES

To characterize aldo-keto reductase 1C3 (AKR1C3) expression in surgically-removed cryptorchid testes. Human AKR1C3 is a monomeric, cytoplasmic, multifunctional enzyme that reduces ketosteroids, ketoprostaglandins, and lipid aldehydes. AKR1C3 expression has been demonstrated in normal adult Leydig cells and peritubular fibromyocytes. No prior studies have evaluated AKR1C3 expression patterns across different age groups.

METHODS

Surgically excised cryptorchid testes were subjected to hematoxylin-eosin evaluation to review overall testicular pathology. These samples were then evaluated for AKR1C3 distribution via immunohistochemical staining with a monospecific AKR1C3 monoclonal antibody. Single-pathologist grading of AKR1C3 expression was correlated with clinical presentations.

RESULTS

A total of 16 cryptorchid testes were identified from the 2000 to present. Median age at the time of surgery was 9 years (range, 1-17). The testes were excised due to atrophy, poor tissue consistency, and short spermatic cord length. AKR1C3 expression was identified at all ages in fibromyocytes surrounding the testicular tubules. Leydig cell expression was absent at Tanner stages 1 and 2, while strong expression was found at Tanner stage 3 and beyond. No AKR1C3 expression was seen in germ cells at any stage. AKR1C3 expression was identified in 18%-26% of Sertoli cells in patients at Tanner stages 2 and beyond.

CONCLUSIONS

AKR1C3 expression occurs in a Tanner stage dependent-fashion. Pre- and peri-pubertal changes appear to promote expression of the enzyme in Leydig cells. In contrast to the normal adult testis, the pediatric cryptorchid testis reveals AKR1C3 expression in Sertoli cells. Additional studies are warranted to determine the involvement of AKR1C3 in testicular descent and development.

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.

Oxidation of PAH trans-dihydrodiols by human aldo-keto reductase AKR1B10

AKR1B10 has been identified as a potential biomarker for human nonsmall cell lung carcinoma and as a tobacco exposure and response gene. AKR1B10 functions as an efficient retinal reductase in vitro and may regulate retinoic acid homeostasis. However, the possibility that this enzyme is able to activate polycyclic aromatic hydrocarbon (PAH) trans-dihydrodiols to form reactive and redox-active o-quinones has not been investigated to date. AKR1B10 was found to oxidize a wide range of PAH trans-dihydrodiol substrates in vitro to yield PAH o-quinones. Reactions of AKR1B10 proceeded with improper stereochemistry, since it was specific for the minor (+)-benzo[a]pyrene-7S,8S-dihydrodiol diastereomer formed in vivo. However, AKR1B10 displayed reasonable activity in the oxidation of both the (-)-R,R and (+)-S,S stereoisomers of benzo[g]chrysene-11,12-dihydrodiol and oxidized the potentially relevant, albeit minor, (+)-benz[a]anthracene-3S,4S-dihydrodiol metabolite. We find that AKR1B10 is therefore likely to play a contributing role in the activation of PAH trans-dihydrodiols in human lung. AKR1B10 retinal reductase activity was confirmed in vitro and found to be 5- to 150-fold greater than the oxidation of PAH trans-dihydrodiols examined. AKR1B10 was highly expressed at the mRNA and protein levels in human lung adenocarcinoma A549 cells, and robust retinal reductase activity was measured in lysates of these cells. The much greater catalytic efficiency of retinal reduction compared to PAH trans-dihydrodiol metabolism suggests AKR1B10 may play a greater role in lung carcinogenesis through dysregulation of retinoic acid homeostasis than through oxidation of PAH trans-dihydrodiols.

Human cytosolic hydroxysteroid dehydrogenases of the aldo-ketoreductase superfamily catalyze reduction of conjugated steroids: implications for phase I and phase II steroid hormone metabolism

Aldo-ketoreductase 1C (AKR1C) enzymes catalyze the NADPH-dependent reduction of ketosteroids to hydroxysteroids. They are Phase I metabolizing enzymes for natural and synthetic steroid hormones. They convert 5alpha-dihydrotestosterone (Dht, potent androgen) to 3alpha/beta-androstanediols (inactive androgens) and the prodrug tibolone (Tib) to estrogenic 3alpha/beta-hydroxytibolones. Herein we demonstrate for the first time that human AKR1C enzymes (AKR1C1-4) are able to reduce conjugated steroids such as Dht-17beta-glucuronide (DhtG), Dht-17beta-sulfate (DhtS), and Tib-17beta-sulfate (TibS). Product identities were characterized by liquid chromatography-mass spectrometry, and kinetic parameters of the reactions were determined. The product profile of the reduction of each steroid conjugate by the individual AKR1C isoform was similar to that of the corresponding free steroid except for the reduction of DhtG catalyzed by AKR1C2, where a complete inversion in stereochemical preference to 3beta-reduction (with DhtG) from 3alpha-reduction (with Dht and DhtS) was observed. The catalytic efficiency of 3-keto reduction was modestly affected by the presence of a 17-sulfate group but severely impaired by the presence of a 17-glucuronide group for AKR1C1-3 isoforms. AKR1C4, however, showed superior catalytic efficiencies versus the other isoforms, and those were unaffected by steroid conjugation. Our findings provide evidence for alternative pathways of steroid metabolism where the phase I reaction (reduction) occurs after the phase II reaction (conjugation). Specifically, it is indicated that Dht is metabolized to its metabolite 3alpha-androstanediol-17-glucuronide via the previously unrecognized "conjugation pathway" involving the sequential reactions of UGT2B17 and AKR1C4 in liver but via the conventional "reduction pathway" involving the sequential reactions of AKR1C2 and UGT2B15/17 in prostate.

Steroid hormone transforming aldo-keto reductases and cancer

Prostate and breast cancer are hormone-dependent malignancies of the aging male and female and require the local production of androgens and estrogens to stimulate cell proliferation. Aldo-keto reductases (AKR) play key roles in this process. In the prostate, AKR1C3 (type 5 17beta-HSD) reduces Delta(4)-androstene-3,17-dione to yield testosterone while AKR1C2 (type 3 3alpha-HSD) eliminates 5alpha-dihydrotestosterone (5alpha-DHT), and AKR1C1 forms 3beta-androstanediol (a ligand for ERbeta). In the breast, AKR1C3 forms testosterone, which is converted to 17beta-estradiol by aromatase or reduces estrone to 17beta-estradiol directly. AKR1C3 also acts as a prostaglandin (PG) F synthase and forms PGF(2alpha) and 11beta-PGF(2alpha), which stimulate the FP receptor and prevent the activation of PPARgamma by PGJ(2) ligands. This proproliferative signaling may stimulate the growth of hormone-dependent and -independent prostate and breast cancer.