The adrenal androgen androstenediol is present in prostate cancer tissue after androgen deprivation therapy and activates mutated androgen receptor

Regulation of Molecular Biomarkers Associated with the Progression of Prostate Cancer

Androgen receptor signaling regulates the normal and pathological growth of the prostate. In particular, the growth and survival of prostate cancer cells is initially dependent on androgen receptor signaling. Exposure to androgen deprivation therapy leads to the development of castration-resistant prostate cancer. There is a multitude of molecular and cellular changes that occur in prostate tumor cells, including the expression of neuroendocrine features and various biomarkers, which promotes the switch of cancer cells to androgen-independent growth. These biomarkers include transcription factors (TP53, REST, BRN2, INSM1, c-Myc), signaling molecules (PTEN, Aurora kinases, retinoblastoma tumor suppressor, calcium-binding proteins), and receptors (glucocorticoid, androgen receptor-variant 7), among others. It is believed that genetic modifications, therapeutic treatments, and changes in the tumor microenvironment are contributing factors to the progression of prostate cancers with significant heterogeneity in their phenotypic characteristics. However, it is not well understood how these phenotypic characteristics and molecular modifications arise under specific treatment conditions. In this work, we summarize some of the most important molecular changes associated with the progression of prostate cancers and we describe some of the factors involved in these cellular processes.

Structure-function of DHEA binding proteins

Dehydroepiandrosterone (3β-hydroxy-5-androsten-17-one, DHEA) and its sulfated metabolite DHEA-S are the most abundant circulating steroids and are precursors for active sex steroid hormones, estradiol and testosterone. DHEA has a broad range of reported effects in the central nervous system (CNS), cardiovascular system, adipose tissue, kidney, liver, and in the reproductive system. The mechanisms by which DHEA and DHEA-S initiate their biological effects are diverse. DHEA and DHEA-S may directly bind to plasma membrane (PM) receptors, including a DHEA-specific, G-protein coupled receptor (GPCR) in endothelial cells; various neuroreceptors, e.g., aminobutyric-acid-type A (GABA(A)), N-methyl-d-aspartate (NMDA) and sigma-1 (S1R) receptors (NMDAR and SIG-1R). DHEA and DHEA-S directly bind the nuclear androgen and estrogen receptors (AR, ERα, or ERβ) although with significantly lower binding affinities compared to the steroid hormones, e.g., testosterone, dihydrotestosterone, and estradiol, which are the cognate ligands for AR and ERs. Thus, extra-gonadal metabolism of DHEA to the sex hormones must be considered for many of the biological benefits of DHEA. DHEA also actives GPER1 (G protein coupled estrogen receptor 1). DHEA activates constitutive androstane receptor CAR (CAR) and proliferator activated receptor (PPARα) by indirect dephosphorylation. DHEA affects voltage-gated sodium and calcium ion channels and DHEA-2 activates TRPM3 (Transient Receptor Potential Cation Channel Subfamily M Member 3). This chapter updates our previous 2018 review pertaining to the physiological, biochemical, and molecular mechanisms of DHEA and DHEA-S activity.

Androgen Deprivation Therapy in High-Risk Localized and Locally Advanced Prostate Cancer

Simple Summary

Androgen deprivation therapy alone is commonly performed for metastatic prostate cancer but is generally not recommended for the treatment of high-risk localized or locally advanced prostate cancer. In this article, we will discuss the position, indications, and future possibilities of ADT for high-risk localized or locally advanced prostate cancer.

Abstract

The recommended treatment for high-risk localized or locally advanced prostate cancer is radical prostatectomy plus extended pelvic lymph node dissection or radiation therapy plus long-term androgen deprivation therapy. However, some patients are treated with androgen deprivation therapy alone for various reasons. In this review, we will discuss the position, indications, complications, and future prospects of androgen deprivation therapy for high-risk localized and locally advanced prostate cancer.

Clinical impact of HSD3B1 polymorphism by metastatic volume and somatic HSD3B1 alterations in advanced prostate cancer

This study aimed to investigate the significance of HSD3B1 gene status including germline polymorphism and somatic alterations in prostate cancer. Patients with prostate cancer treated with androgen-deprivation therapy, as well as tissues from metastatic prostate cancer, were included. Genomic DNA was extracted from cancer tissues and whole blood samples, and HSD3B1 (rs1047303, 1245C) was genotyped by Sanger sequencing. The association of HSD3B1 genotype with progression-free survival according to metastatic volume was examined. Copy number alteration and gene expression of HSD3B1 were examined in prostate cancer cells and public datasets. Among 194 patients, 121 and 73 patients were categorized into low- and high-volume diseases respectively. In multivariate analysis, the adrenal-permissive genotype (AC/CC) was significantly associated with increased risk of progression compared with the adrenal-restrictive genotype (AA) in low volume, but not high-volume diseases. Somatic mutation in HSD3B1 was detected at least in two cases of castration-resistant prostate cancer tissues. HSD3B1 amplification and overexpression were detected in castration-resistant prostate cancer cells and tissues. The current findings suggest that both germline and somatic alterations of HSD3B1 may cooperatively promote castration resistance in prostate cancer and HSD3B1 as a promising biomarker for precision medicine, warranting further investigations.

SEMA3C induces androgen synthesis in prostatic stromal cells through paracrine signaling

BACKGROUND

Castration resistant prostate cancer progression is associated with an acquired intratumoral androgen synthesis. Signaling pathways that can upregulate androgen production in prostate tumor microenvironment are not entirely known. In this study, we investigate the potential effect of a secreted signaling protein named semaphorin 3C (SEMA3C) on steroidogenic activities of prostatic stromal cells.

METHODS

We treated human primary prostate stromal cells (PrSC) with 1uM recombinant SEMA3C protein and androgen precursor named dehydroepiandrosterone (DHEA) 1.7uM. Also, to test SEMA3C's effect on the conversion of DHEA to androgens, we exposed PrSCs to the conditioned media derived from LNCaP cells that were transduced with a lentiviral vector harboring full length SEMA3C gene or empty vector (CM-LN^SEMA3C or CM-LN^Vector ). Then, liquid chromatography-mass spectrometry was performed on steroids isolated from PrSCs media. The messnger RNA expression of steroidogenic enzymes in PrSCs was quantified by quantitative polymerase chain reaction.

RESULTS

Recombinant SEMA3C had no effect on steroidogenic activities in PrSCs. However, key steroidogenic enzymes expression and androgen synthesis were upregulated in PrSCs treated with CM-LN^SEMA3C , compared to those treated with CM-LN^Vector . These results suggest that steroidogenic activities in PrSCs were upregulated in response to a signaling factor in CM-LN^SEMA3C , other than SEMA3C. We hypothesized that SEMA3C overexpression in LNCaP cells affected androgen synthesis in PrSCs through sonic hedgehog (Shh) pathway activation in PrSCs. We verified this effect by blocking Shh signaling with smoothened antagonist.

CONCLUSION

Based on known ability of Shh signaling pathway to activate steroidogenesis in stromal cells, we suggest that SEMA3C overexpression in LNCaP cells can upregulate Shh which in turn is able to stimulate steroidogenic activities in prostatic stromal cells.

A new flavonoid derivative exerts antitumor effects against androgen-sensitive to cabazitaxel-resistant prostate cancer cells

BACKGROUND

Our previous report has shown that the flavonoid 2'-hydroxyflavanone (2'-HF) showed inhibition of androgen receptor (AR) activity against androgen-sensitive prostate cancer (PCa) cells, LNCaP, and exhibited antitumor effects against androgen-insensitive PCa cells, PC-3, and DU145. In the present study, we prepared a derivative of 2'-HF, 16MS7F1924, and confirmed the effects of this derivative on PCa cells.

METHODS

The antiproliferation effects of 16MS7F1924 were investigated in PCa cells using LNCaP, PC-3, DU145 and docetaxel-resistant and cabazitaxel-resistant cell lines of PC-3-TxR/CxR and DU145-TxR/CxR. Prostate-specific antigen (PSA) and AR expression level in whole cells and the nucleus were confirmed in LNCaP by reverse transcriptase polymerase chain reaction and Western blot analysis. AR activity in LNCaP cells was confirmed by luciferase assay using PSA promoter-driven reporter. To analyze the antiproliferative effects, cell-based assays using flow cytometry, immunocytochemistry, and TUNEL assay as well as Western blot analysis were employed. Furthermore, PC-3, DU145 and each chemoresistant strain of human PCa cells were subcutaneously xenografted. The antitumor effects of 16MS7F1924 were evaluated in vivo.

RESULTS

16MS7F1924 showed antitumor effect on all PCa cells in a dose-dependent manner. 16MS7F1924 reduced the expression of PSA messenger RNA (mRNA) and protein and inhibited AR activity in a dose-dependent manner, while expression of AR protein and mRNA was reduced by 16MS7F1924. 16MS7F1924 induced mitotic catastrophe and apoptosis. Apoptotic cells were increased in a dose-dependent manner, and the apoptosis was mediated through the Akt pathway. Tumor growth was safely and significantly inhibited by both intraperitoneal and oral administration of 16MS7F1924 in vivo.

CONCLUSION

16MS7F1924 had sufficient antitumor activity against androgen-sensitive and cabazitaxel-resistant PCa cells and may be useful as a novel therapeutic agent overcoming hormone- and chemoresistant PCas.

A review of the effects and molecular mechanisms of dimethylcurcumin (ASC-J9) on androgen receptor-related diseases

Dimethylcurcumin (ASC-J9) is a curcumin analogue capable of inhibiting prostate cancer cell proliferation. The mechanism is associated with the unique role of ASC-J9 in enhancing androgen receptor (AR) degradation. So far, ASC-J9 has been investigated in typical AR-associated diseases such as prostate cancer, benign prostatic hypertrophy, bladder cancer, renal diseases, liver diseases, cardiovascular diseases, cutaneous wound, spinal and bulbar muscular atrophy, ovarian cancer and melanoma, exhibiting great potentials in disease control. In this review, the effects and molecular mechanisms of ASC-J9 on various AR-associated diseases are summarized. Importantly, the effects of ASC-J9 and AR antagonists enzalutamide/bicalutamide on prostate cancer are compared in detail and crucial differences are highlighted. At last, the pharmacological effects of ASC-J9 are summarized and the future applications of ASC-J9 in AR-associated disease control are discussed.

The Genetic Complexity of Prostate Cancer

Prostate cancer (PCa) is a major concern in public health, with many genetically distinct subsets. Genomic alterations in PCa are extraordinarily complex, and both germline and somatic mutations are of great importance in the development of this tumor. The aim of this review is to provide an overview of genetic changes that can occur in the development of PCa and their role in potential therapeutic approaches. Various pathways and mechanisms proposed to play major roles in PCa are described in detail to provide an overview of current knowledge.

Preclinical profile and phase I clinical trial of a novel androgen receptor antagonist GT0918 in castration-resistant prostate cancer

PURPOSE

We conducted preclinical experiments and phase I clinical trial to investigate the safety, pharmacokinetics (PK) and antitumour effects of GT0918 in castration-resistant prostate cancer (CRPC).

EXPERIMENTAL DESIGN

An androgen receptor (AR) competitive binding assay was performed, followed by evaluation of GT0918 on AR protein expression. The efficacy of GT0918 was investigated in a castration-resistant xenograft model. A phase I dose-escalation study of GT0918 in CRPC was also carried out to evaluate its safety, PK and antitumour efficacy.

RESULTS

GT0918 was demonstrated to inhibit the binding of androgen to AR more potently than MDV3100, and to effectively reduce the AR protein level. GT0918 inhibited the transcriptional activity of wild-type AR and AR with clinically relevant ligand-binding domain mutations. Furthermore, GT0918 significantly inhibited the growth of prostate cancer. A total of 16 patients was treated with GT0918 at five dose levels. Among these 16 patients, 10 and 2 patients, respectively, completed a three-cycle and six-cycle treatment, in which MTD was not reached. All the treatment-related adverse events were grade I, including hypercholesterolemia, hypertriglyceridemia, fatigue and anaemia. PK parameters showed that drug exposure increased with dose proportionally from 50 to 300 mg and a saturation was observed between 300 and 400 mg. PSA declines of ≥30% and ≥50% were, respectively, observed in six and two cases. All the 12 patients with metastatic soft tissue lesions confirmed stable disease.

CONCLUSIONS

GT0918, a full AR antagonist without agonist effect, has high binding affinity to AR with AR protein down-regulation activity. GT0918 is demonstrated to be well tolerated with a favourable PK profile and exhibits promising antitumour activity in CRPC. CLINICALTRIALS: gov identifier CTR20150501.

Systematically understanding the immunity leading to CRPC progression

Prostate cancer (PCa) is the most commonly diagnosed malignancy and the second leading cause of cancer-related death in American men. Androgen deprivation therapy (ADT) has become a standard treatment strategy for advanced PCa. Although a majority of patients initially respond to ADT well, most of them will eventually develop castration-resistant PCa (CRPC). Previous studies suggest that ADT-induced changes in the immune microenvironment (mE) in PCa might be responsible for the failures of various therapies. However, the role of the immune system in CRPC development remains unclear. To systematically understand the immunity leading to CRPC progression and predict the optimal treatment strategy in silico, we developed a 3D Hybrid Multi-scale Model (HMSM), consisting of an ODE system and an agent-based model (ABM), to manipulate the tumor growth in a defined immune system. Based on our analysis, we revealed that the key factors (e.g. WNT5A, TRAIL, CSF1, etc.) mediated the activation of PC-Treg and PC-TAM interaction pathways, which induced the immunosuppression during CRPC progression. Our HMSM model also provided an optimal therapeutic strategy for improving the outcomes of PCa treatment.

Prostate cancer (PCa) is the second leading cause of cancer-related deaths in American men. Androgen deprivation therapy (ADT) is the first-line therapy for advanced PCa, yet a significant number of primary PCa patients treated with ADT eventually develop incurable castration-resistant prostate cancer (CRPC). Recent observations suggest that the immunosuppressive microenvironment of PCa might be responsible for the failures of various therapies. However, the role of immune system in CRPC progression is still unclear. To deeply understand the immunity leading to CRPC progression, we developed a unique systems biology approach (HMSM). Based on our analysis, we identified the key molecules (e.g. WNT5A, TRAIL, CSF1, etc.) mediating the communication of PCa and immune cells. Our HMSM system also revealed the optimal therapeutic strategy for PCa treatment. Collectively, our study provides a new insight to study tumor-related immune mechanisms and pave the way for the development of more effective treatments.

A Comprehensive Analysis of Steroid Hormones and Progression of Localized High-Risk Prostate Cancer

BACKGROUND

In men with localized prostate cancer who are undergoing radical prostatectomy (RP), it is uncertain whether their systemic hormonal environment is associated with outcomes. The objective of the study was to examine the association between the circulating steroid metabolome with prognostic factors and progression.

METHODS

The prospective PROCURE cohort was recruited from 2007 to 2012, and comprises 1,766 patients with localized prostate cancer who provided blood samples prior to RP. The levels of 15 steroids were measured in plasma using mass spectrometry, and their association with prognostic factors and disease-free survival (DFS) was established with logistic regression and multivariable Cox proportional hazard models.

RESULTS

The median follow-up time after surgery was 73.2 months. Overall, 524 patients experienced biochemical failure and 75 developed metastatic disease. Testosterone and androsterone levels were higher in low-risk disease. Associations were observed between adrenal precursors and risk of cancer progression. In high-risk patients, a one-unit increment in log-transformed androstenediol (A5diol) and dehydroepiandrosterone-sulfate (DHEA-S) levels were linked to DFS with HR of 1.47 (P = 0.0017; q = 0.026) and 1.24 (P = 0.043; q = 0.323), respectively. Although the number of metastatic events was limited, trends with metastasis-free survival were observed for A5diol (HR = 1.51; P = 0.057) and DHEA-S levels (HR = 1.43; P = 0.054).

CONCLUSIONS

In men with localized prostate cancer, our data suggest that the preoperative steroid metabolome is associated with the risk of recurrence of high-risk disease.

IMPACT

The associations of adrenal androgens with progression of localized high-risk disease could help refine hormonal strategies for these patients.

Canonical and Noncanonical Androgen Metabolism and Activity

Androgens are critical drivers of prostate cancer. In this chapter we first discuss the canonical pathways of androgen metabolism and their alterations in prostate cancer progression, including the classical, backdoor and 5α-dione pathways, the role of pre-receptor DHT metabolism, and recent findings on oncogenic splicing of steroidogenic enzymes. Next, we discuss the activity and metabolism of non-canonical 11-oxygenated androgens that can activate wild-type AR and are less susceptible to glucuronidation and inactivation than the canonical androgens, thereby serving as an under-recognized reservoir of active ligands. We then discuss an emerging literature on the potential non-canonical role of androgen metabolizing enzymes in driving prostate cancer. We conclude by discussing the potential implications of these findings for prostate cancer progression, particularly in context of new agents such as abiraterone and enzalutamide, which target the AR-axis for prostate cancer therapy, including mechanisms of response and resistance and implications of these findings for future therapy.

Prospective serum metabolomic profile of prostate cancer by size and extent of primary tumor

Two recent investigations found serum lipid and energy metabolites related to aggressive prostate cancer up to 20 years prior to diagnosis. To elucidate whether those metabolomic profiles represent etiologic or tumor biomarker signals, we prospectively examined serum metabolites of prostate cancer cases by size and extent of primary tumors in a nested case-control analysis in the ATBC Study cohort that compared cases diagnosed with T2 (n = 71), T3 (n = 51), or T4 (n = 15) disease to controls (n = 200). Time from fasting serum collection to diagnosis averaged 10 years (range 1-20). LC/MS-GC/MS identified 625 known compounds, and logistic regression estimated odds ratios (ORs) associated with one-standard deviation differences in log-metabolites. N-acetyl-3-methylhistidine, 3-methylhistidine and 2'-deoxyuridine were elevated in men with T2 cancers compared to controls (ORs = 1.38-1.79; 0.0002 ≤ p ≤ 0.01). By contrast, four lipid metabolites were inversely associated with T3 tumors: oleoyl-linoleoyl-glycerophosphoinositol (GPI), palmitoyl-linoleoyl-GPI, cholate, and inositol 1-phosphate (ORs = 0.49-0.60; 0.000017 ≤ p ≤ 0.003). Secondary bile acid lipids, sex steroids and caffeine-related xanthine metabolites were elevated, while two Krebs cycle metabolites were decreased, in men diagnosed with T4 cancers. Men with T2, T3, and T4 prostate cancer primaries exhibit qualitatively different metabolite profiles years in advance of diagnosis that may represent etiologic factors, molecular patterns reflective of distinct primary tumors, or a combination of both.

Sex steroids in the tumor microenvironment and prostate cancer progression

Prostate cancer is uniquely dependent on androgens. Despite years of research on the relationship between androgens and prostate cancer, many questions remain as to the biological effects of androgens and other sex steroids during prostate cancer progression. This article reviews the clinical and basic research on the influence of sex steroids such as androgens, estrogens and progesterone within the prostate tumor microenvironment on the progression of prostate cancer. We review clinical studies to date evaluating serum sex steroids as prognostic biomarkers and discuss their respective biological effects within the prostate tumor microenvironment. We also review the link between genomic alterations and sex steroid levels within prostate tumors. Finally, we highlight the links between sex steroid levels and the function of the immune system within the tumor microenvironment. As the context of treatment of lethal prostate cancer evolves over time, an understanding of this underlying biology remains central to developing optimal treatment approaches.

Antiandrogens Reduce Intratumoral Androgen Concentrations and Induce Androgen Receptor Expression in Castration-Resistant Prostate Cancer Xenografts

The development of castration-resistant prostate cancer (CRPC) is associated with the activation of intratumoral androgen biosynthesis and an increase in androgen receptor (AR) expression. We recently demonstrated that, similarly to the clinical CRPC, orthotopically grown castration-resistant VCaP (CR-VCaP) xenografts express high levels of AR and retain intratumoral androgen concentrations similar to tumors grown in intact mice. Herein, we show that antiandrogen treatment (enzalutamide or ARN-509) significantly reduced (10-fold, P < 0.01) intratumoral testosterone and dihydrotestosterone concentrations in the CR-VCaP tumors, indicating that the reduction in intratumoral androgens is a novel mechanism by which antiandrogens mediate their effects in CRPC. Antiandrogen treatment also altered the expression of multiple enzymes potentially involved in steroid metabolism. Identical to clinical CRPC, the expression levels of the full-length AR (twofold, P < 0.05) and the AR splice variants 1 (threefold, P < 0.05) and 7 (threefold, P < 0.01) were further increased in the antiandrogen-treated tumors. Nonsignificant effects were observed in the expression of certain classic androgen-regulated genes, such as TMPRSS2 and KLK3, despite the low levels of testosterone and dihydrotestosterone. However, other genes recently identified to be highly sensitive to androgen-regulated AR action, such as NOV and ST6GalNAc1, were markedly altered, which indicated reduced androgen action. Taken together, the data indicate that, besides blocking AR, antiandrogens modify androgen signaling in CR-VCaP xenografts at multiple levels.

Circulating steroid hormone variations throughout different stages of prostate cancer

Steroid hormones play a central role in the maintenance and progression of prostate cancer. The androgen receptor is the primary driver of tumor cell proliferation and is activated by the androgens testosterone and 5α-dihydrotestosterone. Inhibition of this pathway through medical or surgical castration improves survival in the majority of advanced prostate cancer patients. However, conversion of adrenal androgen precursors and alternative steroidogenic pathways have been found to contribute to tumor progression and resistance to treatment. The emergence of highly accurate detection methods allows us to study steroidogenic mechanisms in more detail, even after treatment with potent steroidogenic inhibitors such as the CYP17A1 inhibitor abiraterone. A clear overview of steroid hormone levels in patients throughout the local, metastatic and castration-resistant stages of prostate cancer and treatment modalities is key toward a better understanding of their role in tumor progression and treatment resistance. In this review, we summarize the currently available data on steroid hormones that have been implicated in the various stages of prostate cancer. Additionally, this review addresses the implications of these findings, highlights important studies in this field and identifies current gaps in literature.

Clinical relevance of androgen receptor alterations in prostate cancer

Prostate cancer (PC) remains a leading cause of cancer-related deaths among men worldwide, despite continuously improved treatment strategies. Patients with metastatic disease are treated by androgen deprivation therapy (ADT) that with time results in the development of castration-resistant prostate cancer (CRPC) usually established as metastases within bone tissue. The androgen receptor (AR) transcription factor is the main driver of CRPC development and of acquired resistance to drugs given for treatment of CRPC, while a minority of patients have CRPC that is non-AR driven. Molecular mechanisms behind epithelial AR reactivation in CRPC include AR gene amplification and overexpression, AR mutations, expression of constitutively active AR variants, intra-tumoural and adrenal androgen synthesis and promiscuous AR activation by other factors. This review will summarize AR alterations of clinical relevance for patients with CRPC, with focus on constitutively active AR variants, their possible association with AR amplification and structural rearrangements as well as their ability to predict patient resistance to AR targeting drugs. The review will also discuss AR signalling in the tumour microenvironment and its possible relevance for metastatic growth and therapy.

Metabolomic Profiling of Serum Retinol in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study

The role of retinol in the prevention of multifactorial chronic diseases remains uncertain, and there is sparse evidence regarding biological actions and pathways implicated in its effects on various outcomes. The aim is to investigate whether serum retinol in an un-supplemented state is associated with low molecular weight circulating metabolites. We performed a metabolomic analysis of 1,282 male smoker participants based on pre-supplementation fasting serum in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study. We examined the association between 947 metabolites measured by ultra-high performance LC-MS/GC-MS and retinol concentration (from HPLC) using linear regression that estimated the difference in metabolite concentrations per unit difference in retinol concentration as standardized β-coefficients and standard errors (SE). We identified 63 metabolites associated with serum retinol below the Bonferroni-corrected P-value (p < 5.3 × 10^–5). The strongest signals were for N-acetyltryptophan (β = 0.27; SE = 0.032; p = 9.8 × 10⁻¹⁷), myo-inositol (β = 0.23; SE = 0.032; p = 9.8 × 10⁻¹³), and 1-palmitoylglycerophosphoethanolamine (β = 0.22; SE = 0.032; p = 3.2 × 10⁻¹²). Several chemical class pathways were strongly associated with retinol, including amino acids (p = 1.6 × 10⁻¹⁰), lipids (p = 3.3 × 10^–7), and cofactor/vitamin metabolites (3.3 × 10⁻⁷). The strongest sub-pathway association was for inositol metabolism (p = 2.0 × 10^–14). Serum retinol concentration is associated with circulating metabolites in various metabolic pathways, particularly lipids, amino acids, and cofactors/vitamins. These interrelationships may have relevance to the biological actions of retinol, including its role in carcinogenesis.

Testosterone and dihydrotestosterone levels in the transition zone correlate with prostate volume

BACKGROUND

There is still no consensus regarding intraprostatic androgen levels and the accumulation of androgens in the hyperplastic prostatic tissue. The current opinion is that intraprostatic dihydrotestosterone (DHT) concentrations are maintained but not elevated in benign prostatic hyperplasia (BPH), while there is no similar data concerning intraprostatic testosterone (T).

METHODS

Tissue T (tT) and tissue DHT (tDHT) concentration were determined in 93 patients scheduled for initial prostate biopsy. The criteria for biopsy were abnormal DRE and/or PSA > 4 ng/mL. Total prostate volume (TPV) was determined by transrectal ultrasound (TRUS). During TRUS- guided prostate biopsy, 10-12 samples were collected from the peripheral zone (PZ) and two additional samples were collected from the transition zone (TZ). The samples from the TZ were immediately frozen in liquid nitrogen at -70°C, and transported for tissue androgen determination, using liquid chromatography mass spectrometry (LC-MS).

RESULTS

Pathological analysis revealed that prostate cancer (PCa) was present in 45 and absent in 48 patients. In the whole group, there were 42 men with small prostate (TPV < 30 mL) and 51 with enlarged prostate (TPV ≥ 31 mL). The overall average tT level was 0.79 ± 0.66 ng/g, while the average tDHT level was 10.27 ± 7.15 ng/g. There were no differences in tT and tDHT level in prostates with and without PCa. However, tT and tDHT levels were significantly higher in larger, than in smaller prostates (tT: 1.05 ± 0.75 and 0.46 ± 0.29 ng/g, and tDHT: 15.0 ± 6.09 and 4.51 ± 2.75 ng/g, respectively). There were strong correlations between tT and TPV (r = 0.71), and tDHT and TPV (r = 0.74).

CONCLUSIONS

The present study confirmed that both T and DHT accumulated in the stroma of enlarged prostates; the degree of accumulation correlated with prostate volume.

A Phase II, Randomized, Open-Label Study of Neoadjuvant Degarelix versus LHRH Agonist in Prostate Cancer Patients Prior to Radical Prostatectomy

Purpose: Degarelix, a new gonadotropin-releasing hormone (GnRH) receptor antagonist with demonstrated efficacy as first-line treatment in the management of high-risk prostate cancer, possesses some theoretical advantages over luteinizing hormone-releasing hormone (LHRH) analogues in terms of avoiding "testosterone flare" and lower follicle-stimulating hormone (FSH) levels. We set out to determine whether preoperative degarelix influenced surrogates of disease control in a randomized phase II study.Experimental Design: Thirty-nine patients were randomly assigned to one of three different neoadjuvant arms: degarelix only, degarelix/bicalutamide, or LHRH agonist/bicalutamide. Treatments were given for 3 months before prostatectomy. Patients had localized prostate cancer and had chosen radical prostatectomy as primary treatment. The primary end point was treatment effect on intratumoral dihydrotestosterone levels.Results: Intratumoral DHT levels were higher in the degarelix arm than both the degarelix/bicalutamide and LHRH agonist/bicalutamide arms (0.87 ng/g vs. 0.26 ng/g and 0.23 ng/g, P < 0.01). No significant differences existed for other intratumoral androgens, such as testosterone and dehydroepiandrosterone. Patients in the degarelix-only arm had higher AMACR levels on immunohistochemical analysis (P = 0.01). Serum FSH levels were lower after 12 weeks of therapy in both degarelix arms than the LHRH agonist/bicalutamide arm (0.55 and 0.65 vs. 3.65, P < 0.01), and inhibin B levels were lower in the degarelix/bicalutamide arm than the LHRH agonist/bicalutamide arm (82.14 vs. 126.67, P = 0.02).Conclusions: Neoadjuvant degarelix alone, compared with use of LHRH agonist and bicalutamide, is associated with higher levels of intratumoral dihydrotestosterone, despite similar testosterone levels. Further studies that evaluate the mechanisms behind these results are needed. Clin Cancer Res; 23(8); 1974-80. ©2016 AACR.

Advances in hormonal therapies for hormone naïve and castration-resistant prostate cancers with or without previous chemotherapy

Hormonal manipulation plays a significant role in the treatment of advanced hormone naïve prostate cancer and castration-resistant prostate cancer (CRPC) with or without previous chemotherapy. Combination of gonadotropin releasing hormone (GnRH) agonists and androgen receptor (AR) antagonists (combined androgen blockade; CAB) is the first line therapy for advanced hormone naïve prostate cancer, but current strategies are developing novel GnRH antagonists to overcome disadvantages associated with GnRH agonist monotherapy and CAB in the clinical setting. Abiraterone acetate and enzalutamide are hormonal agents currently available for patients with CRPC and are both shown to improve overall survival versus placebo. Recently, in clinical trials, testosterone has been administered in cycles with existing surgical and chemical androgen deprivation therapies (ADT) (intermittent therapy) to CRPC patients of different stages (low risk, metastatic) to abate symptoms of testosterone deficiency and reduce cost of treatment from current hormonal therapies for patients with CRPC. This review will provide an overview on the therapeutic roles of hormonal manipulation in advanced hormone naïve and castration-resistant prostate cancers, as well as the development of novel hormonal therapies currently in preclinical and clinical trials.

Understanding and overcoming the mechanisms of primary and acquired resistance to abiraterone and enzalutamide in castration resistant prostate cancer

In recent years, in castration resistant prostate cancer (CRPC), several new drugs have been approved that prolong overall survival, including enzalutamide and abiraterone, two new-generation hormonal therapies. Despite the demonstrated benefit of these agents, not all patients with CRPC are responsive to treatment, the gain in median progression-free survival with these therapies compared to standard of care is, rather disappointingly, still less than six months and the appearance of acquired resistance is almost universal. Approximately one third of patients treated with abiraterone and 25% of those treated with enzalutamide show primary resistance to these agents. Even if the mechanisms of resistance to these agents are not fully defined, many hypotheses are emerging, including systemic and intratumoral androgen biosynthesis up-regulation, androgen receptor (AR) gene mutations and amplifications, alteration of pathways involved in cross-talk with AR signaling, glucocorticoid receptor overexpression, neuroendocrine differentiation, immune system deregulation and others. The aim of this paper is to review currently available data about mechanisms of resistance to abiraterone and enzalutamide, and to discuss how these mechanisms could be potentially overcome through novel therapeutic agents.

New developments in the treatment of castration resistant prostate cancer

In the past 5 years, the treatment and understanding of metastatic castrate resistant prostate cancer (CRPC) have improved dramatically. Our understanding of the mechanisms of castration resistance has allowed for the development of new drugs to target prostate cancer, and our understanding of genetic mutations may give us new tools with which to more accurately diagnose and be able to predict the course of this heterogeneous disease. This article summarizes the recent advances in the understanding of the development of CRPC, as well as the new drugs and targets, which have evolved from this basic research.

Reconsideration of progression to CRPC during androgen deprivation therapy

Androgen blockade-naïve prostate cancer (PCa) develops into CRPC during androgen deprivation therapy (ADT) by various genetic actions. The androgen-AR signaling axis plays a key role in this development. PCa cells mainly adapt themselves to the environment of lower androgen concentrations and change into androgen-hypersensitive cells or androgen-independent cells. Androgens of adrenal origin and their metabolites synthesized in the microenvironment in an intracrine/paracrine fashion act on surviving PCa cells and secrete prostate specific antigen (PSA). Total androgen deprivation (TAD) (castration, antiandrogen, and CYP17A1 inhibitor) can become an effective therapeutic strategy concerning the androgen signaling axis-related pathway. However, it is important to ascertain whether elevation of serum PSA results from AR activation or from an androgen-independent tumor volume effect. Then, clinicians can judge it adequately using the imaging studies such as CT or bone scan as well as PSA and bone metabolic markers, an approach which is necessary to judge which treatment is most suitable for the CRPC patients. This article is part of a Special Issue entitled 'Essential role of DHEA'.

Combined blockade of testicular and locally made androgens in prostate cancer: a highly significant medical progress based upon intracrinology

Recently two drugs, namely the antiandrogen MDV-3100 and the inhibitor of 17α-hydroxylase abiraterone have been accepted by the FDA for the treatment of castration-resistant prostate cancer (CRPC) with or without previous chemotherapy, with a prolongation of overall survival of 2.2-4.8 months. While medical (GnRH agonist) or surgical castration reduces the serum levels of testosterone by about 97%, an important concentration of testosterone and dihydrotestosterone remains in the prostate and activates the androgen receptor (AR), thus offering an explanation for the positive data obtained in CRPC. In fact, explanation of the response observed with MDV-3100 or enzalutamide in CRPC is essentially a blockade of the action or formation of intraprostatic androgens. In addition to the inhibition of the action or formation of androgens made locally by the mechanisms of intracrinology, increased AR levels and AR mutations can be involved, especially in very advanced disease. Future developments look at more efficient inhibitors of the action or formation of intraprostatic androgens and starting treatment earlier when blockade of androgens can exert long-term control and even cure prostate cancer treated at a stage before the appearance of metastases. This article is part of a Special Issue entitled 'Essential role of DHEA'.

Targeted prodrug approaches for hormone refractory prostate cancer

Due to the propensity of relapse and resistance with prolonged androgen deprivation therapy (ADT), there is a growing interest in developing non-hormonal therapeutic approaches as alternative treatment modalities for hormone refractory prostate cancer (HRPC). Although the standard treatment for HRPC consists of a combination of ADT with taxanes and anthracyclines, the clinical use of chemotherapeutics is limited by systemic toxicity stemming from nondiscriminatory drug exposure to normal tissues. In order to improve the tumor selectivity of chemotherapeutics, various targeted prodrug approaches have been explored. Antibody-directed enzyme prodrug therapy (ADEPT) and gene-directed enzyme prodrug therapy (GDEPT) strategies leverage tumor-specific antigens and transcription factors for the specific delivery of cytotoxic anticancer agents using various prodrug-activating enzymes. In prostate cancer, overexpression of tumor-specific proteases such as prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA) is being exploited for selective activation of anticancer prodrugs designed to be activated through proteolysis by these prostate cancer-specific enzymes. PSMA- and PSA-activated prodrugs typically comprise an engineered high-specificity protease peptide substrate coupled to a potent cytotoxic agent via a linker for rapid release of cytotoxic species in the vicinity of prostate cancer cells following proteolytic cleavage. Over the past two decades, various such prodrugs have been developed and they were effective at inhibiting prostate tumor growth in rodent models; several of these prodrug approaches have been advanced to clinical trials and may be developed into effective therapies for HRPC.

A phase 2 trial of abiraterone acetate in Japanese men with metastatic castration-resistant prostate cancer and without prior chemotherapy (JPN-201 study)

Objective

Abiraterone acetate has been approved in >70 countries for chemotherapy-naïve metastatic castration-resistant prostate cancer patients. Efficacy and safety of abiraterone acetate (1000 mg/once daily) with prednisolone (5 mg/twice daily) in chemotherapy-naïve Japanese patients with metastatic castration-resistant prostate cancer was evaluated.

Methods

Men, ≥20 years, with prostate-specific antigen levels of ≥5 ng/ml and evidence of progression were enrolled in this Phase 2, multicenter, open-label study. Primary efficacy endpoint was proportion of patients achieving a prostate-specific antigen decline of ≥50% from baseline (prostate-specific antigen response) after 12 week of treatment. Secondary efficacy endpoints and safety were assessed.

Results

A confirmed prostate-specific antigen response was observed in 29/48 (60.4%) patients by week 12; lower limit of two-sided 90% confidence interval was >35% (threshold response rate), demonstrating efficacy of abiraterone acetate. Secondary efficacy endpoints: prostate-specific antigen response rate during treatment period: 62.5%; objective radiographic response, partial response: 4/18 (22.2%) patients; complete response: none; stable disease: 11/18 (61.1%) patients; median percent change in prostate-specific antigen level from baseline at Week 12: −66.62%. Median prostate-specific antigen response duration and progression-free survival were not reached, and median radiographic progression-free survival was 253 days. Of 31/48 (64.6%) patients experienced adverse events of special interest; most common was hepatic function abnormality (37.5%, Grade 3: 10.4%). One Grade 3 hypertension was the only mineralocorticoid adverse event >Grade 1/2.

Conclusions

Efficacy of abiraterone acetate plus prednisolone was demonstrated by decline in prostate-specific antigen levels with evidence of antitumor activity by radiography in Japanese patients with chemotherapy-naïve metastatic castration-resistant prostate cancer. Abiraterone acetate plus prednisolone had an acceptable safety profile.

Clinical trial registration no

NCT01756638.

Phase-1 study of abiraterone acetate in chemotherapy-naïve Japanese patients with castration-resistant prostate cancer

Persistent androgen synthesis under castration status in adrenal gland, testes and tumor cells is thought to be one of the major causes of development and progression of castration-resistant prostate cancer (CRPC). Abiraterone acetate (AA), the prodrug of abiraterone, which is an inhibitor of androgen synthesis enzymes, was evaluated for pharmacokinetics, pharmacodynamics, preliminary efficacy and safety in Japanese patients with CRPC in a phase-1, open-label and dose-escalation study. Chemotherapy-naïve Japanese CRPC patients (N = 27) received one of four AA daily doses (250 mg [n = 9], 500 mg [n = 6], 1000 [1 h premeal] mg [n = 6] and 1000 [2 h postmeal] mg [n = 6]) continuously through 28-day treatment cycles. In the first cycle, AA monotherapy was given on days 1–7 for pharmacokinetics, and AA plus prednisone (5 mg twice daily) from days 8 to 28. Of 27 patients, 9 continued treatment with AA until the data cut-off date (18 July 2013). Over the evaluated dose range, plasma abiraterone concentrations increased with dose, with median t_max 2–3 h. At each dose level, mean serum corticosterone concentrations increased, while testosterone and dehydroepiandrosterone sulfate concentrations rapidly decreased following a single AA dose and were further reduced to near the quantification limit on day 8 regardless of the dose. At least 3 patients from each dose-group experienced ≥50% prostate-specific antigen reduction, suggesting clinical benefit from AA in Japanese CRPC patients. AA was generally well-tolerated, and, therefore, the recommended AA dosage regimen in Japanese CRPC patients is 1000 mg oral dose under modified fasting conditions (at least 1 h premeal or 2 h postmeal). This study is registered at ClinicalTrials.gov: NCT01186484.

High testosterone levels in prostate tissue obtained by needle biopsy correlate with poor-prognosis factors in prostate cancer patients

Background

There is currently no consensus on the correlations between androgen concentrations in prostate tissue and blood and stage and pathological grade of prostate cancer. In this study, we used a newly-developed ultra-sensitive liquid-chromatography tandem mass spectrometry method to measure testosterone (T) and dihydrotestosterone (DHT) concentrations in blood and needle biopsy prostate specimens from patients with prostate cancer.

Methods

We analyzed androgen levels in 196 men diagnosed with prostate cancer. All patients had undergone systematic needle biopsy, and an additional needle biopsy from the peripheral zone was conducted for the simultaneous determination of T and DHT. We analyzed the relationships between T and DHT levels in tissue and blood and Gleason score, clinical stage, and percentage of positive biopsy cores, using multivariate analysis.

Results

The median T and DHT levels in blood were 3551.0 pg/mL and 330.5 pg/mL, respectively. There was a strong correlation between serum T and DHT. The median T and DHT levels in prostate tissue were 0.5667 pg/mg and 7.0625 pg/mg, respectively. In multivariate analysis, serum prostate-specific antigen and tissue T levels were significantly associated with poor prognosis; high T levels in prostate tissue were significantly related to high Gleason score (p = 0.041), advanced clinical stage (p = 0.002), and a high percentage of positive biopsy cores (p = 0.001).

Conclusions

The results of this study indicate that high T levels in prostate tissue are related to high Gleason score, advanced clinical stage, and a high percentage of positive biopsy cores in patients with prostate cancer. T level in needle biopsy specimens may therefore be a useful prognostic factor in prostate cancer patients.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-717) contains supplementary material, which is available to authorized users.

Sex steroid metabolism in benign and malignant intact prostate biopsies: individual profiling of prostate intracrinology

In vitro studies reveal that androgens, oestrogens, and their metabolites play a crucial role in prostate homeostasis. Most of the studies evaluated intraprostatic hormone metabolism using cell lines or preprocessed specimens. Using an ex vivo model of intact tissue cultures with preserved architecture, we characterized the enzymatic profile of biopsies from patients with benign prostatic hyperplasia (BPH) or cancer (PC), focusing on 17β-hydroxy-steroid-dehydrogenases (17β-HSDs) and aromatase activities. Samples from 26 men who underwent prostate needle core biopsies (BPH n = 14; PC n = 12) were incubated with radiolabeled ³H-testosterone or ³H-androstenedione. Conversion was evaluated by TLC separation and beta-scanning of extracted supernatants. We identified three major patterns of conversion. The majority of BPHs revealed no active testosterone/oestradiol conversion as opposed to prostate cancer. Conversion correlated with histology and PSA, but not circulating hormones. Highest Gleason scores had a higher androstenedion-to-testosterone conversion and expression of 17β-HSD-isoenzymes-3/5. Conclusions. We developed an easy tool to profile individual intraprostatic enzymatic activity by characterizing conversion pathways in an intact tissue environment. In fresh biopsies we found that 17β-HSD-isoenzymes and aromatase activities correlate with biological behaviour allowing for morphofunctional phenotyping of pathology specimens and clinical monitoring of novel enzyme-targeting drugs.

Strategies for targeting the androgen receptor axis in prostate cancer

Androgen receptor (AR) signaling plays a critical role in prostate cancer cell proliferation, survival, and differentiation. Therapeutic strategies targeting the androgen receptor have been developed for the treatment of metastatic hormone-naïve prostate cancer; however, despite effective targeting recent studies have demonstrated that during progression to a castrate-resistant phenotype there is restoration of AR target gene expression. On the basis of this observation, second-generation therapeutics have been developed to target AR in the castrate-resistant setting resulting in a survival benefit. In this review we will discuss the mechanisms promoting AR signaling and the development of second-generation therapeutics targeting AR in castrate-resistant prostate cancer.

GnRH agonists and the rapidly increasing use of combined androgen blockade in prostate cancer

The discovery of medical castration with GnRH agonists in 1979 rapidly replaced surgical castration and high doses of estrogens for the treatment of prostate cancer. Soon afterwards, it was discovered that androgens were made locally in the prostate from the inactive precursor DHEA of adrenal origin, a mechanism called intracrinology. Taking into account these novel facts, combined androgen blockade (CAB) using a pure antiandrogen combined with castration in order to block the two sources of androgens was first published in 1982. CAB was the first treatment shown in randomized and placebo-controlled trials to prolong life in prostate cancer, even at the metastatic stage. Most importantly, the results recently obtained with the novel pure antiandrogen enzalutamide as well as with abiraterone, an inhibitor of 17α-hydroxylase in castration-resistant prostate cancer, has revitalized the CAB concept. The effects of CAB observed on survival of heavily pretreated patients further demonstrates the importance of the androgens made locally in the prostate and are a strong motivation to apply CAB to efficiently block all sources of androgens earlier at start of treatment and, even better, before metastasis occurs. The future of research in this field thus seems to be centered on the development of more potent blockers of androgens formation and action in order to obtain better results at the metastatic stage and, for the localized stage, reduce the duration of treatment required to achieve complete apoptosis and control of prostate cancer proliferation before it reaches the metastatic or noncurable stage.

Dehydroepiandrosterone-induces miR-21 transcription in HepG2 cells through estrogen receptor β and androgen receptor

Although oncomiR miR-21 is highly expressed in liver and overexpressed in hepatocellular carcinoma (HCC), its regulation is uncharacterized. We examined the effect of physiologically relevant nanomolar concentrations of dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEA-S) on miR-21 expression in HepG2 human hepatoma cells. 10nM DHEA and DHEA-S increase pri-miR-21 transcription in HepG2 cells. Dietary DHEA increased miR-21 in vivo in mouse liver. siRNA and inhibitor studies suggest that DHEA-S requires desulfation for activity and that DHEA-induced pri-miR-21 transcription involves metabolism to androgen and estrogen receptor (AR and ER) ligands. Activation of ERβ and AR by DHEA metabolites androst-5-ene-3,17-dione (ADIONE), androst-5-ene-3β,17β-diol (ADIOL), dihydrotestosterone (DHT), and 5α-androstane-3β,17β-diol (3β-Adiol) increased miR-21 transcription. DHEA-induced miR-21 increased cell proliferation and decreased Pdcd4 protein, a bona fide miR-21. Estradiol (E2) inhibited miR-21 expression via ERα. DHEA increased ERβ and AR recruitment to the miR-21 promoter within the VMP1/TMEM49 gene, with possible significance in hepatocellular carcinoma.

Castration induces up-regulation of intratumoral androgen biosynthesis and androgen receptor expression in an orthotopic VCaP human prostate cancer xenograft model

Androgens are key factors involved in the development and progression of prostate cancer (PCa), and PCa growth can be suppressed by androgen deprivation therapy. In a considerable proportion of men receiving androgen deprivation therapy, however, PCa progresses to castration-resistant PCa (CRPC), making the development of efficient therapies challenging. We used an orthotopic VCaP human PCa xenograft model to study cellular and molecular changes in tumors after androgen deprivation therapy (castration). Tumor growth was monitored through weekly serum prostate-specific antigen measurements, and mice with recurrent tumors after castration were randomized to treatment groups. Serum prostate-specific antigen concentrations showed significant correlation with tumor volume. Castration-resistant tumors retained concentrations of intratumoral androgen (androstenedione, testosterone, and 5α-dihydrotestosterone) at levels similar to tumors growing in intact hosts. Accordingly, castration induced up-regulation of enzymes involved in androgen synthesis (CYP17A1, AKR1C3, and HSD17B6), as well as expression of full-length androgen receptor (AR) and AR splice variants (AR-V1 and AR-V7). Furthermore, AR target gene expression was maintained in castration-resistant xenografts. The AR antagonists enzalutamide (MDV3100) and ARN-509 suppressed PSA production of castration-resistant tumors, confirming the androgen dependency of these tumors. Taken together, the findings demonstrate that our VCaP xenograft model exhibits the key characteristics of clinical CRPC and thus provides a valuable tool for identifying druggable targets and for testing therapeutic strategies targeting AR signaling in CRPC.

Beyond T and DHT - novel steroid derivatives capable of wild type androgen receptor activation

While androgen deprivation therapy (ADT) remains the primary treatment for metastatic prostate cancer (PCa), castration does not eliminate androgens from the prostate tumor microenvironment, and residual intratumoral androgens are implicated in nearly every mechanism by which androgen receptor (AR)-mediated signaling promotes castration-resistant disease. The uptake and intratumoral (intracrine) conversion of circulating adrenal androgens such as dehydroepiandrosterone sulfate (DHEA-S) to steroids capable of activating the wild type AR is a recognized driver of castration resistant prostate cancer (CRPC). However, less well-characterized adrenal steroids, including 11-deoxcorticosterone (DOC) and 11beta-hydroxyandrostenedione (11OH-AED) may also play a previously unrecognized role in promoting AR activation. In particular, recent data demonstrate that the 5α-reduced metabolites of DOC and 11OH-AED are activators of the wild type AR. Given the well-recognized presence of SRD5A activity in CRPC tissue, these observations suggest that in the low androgen environment of CRPC, alternative sources of 5α-reduced ligands may supplement AR activation normally mediated by the canonical 5α-reduced agonist, 5α-DHT. Herein we review the emerging data that suggests a role for these alternative steroids of adrenal origin in activating the AR, and discuss the enzymatic pathways and novel downstream metabolites mediating these effects. We conclude by discussing the potential implications of these findings for CRPC progression, particularly in context of new agents such as abiraterone and enzalutamide which target the AR-axis for prostate cancer therapy.

Androgen receptor functions in castration-resistant prostate cancer and mechanisms of resistance to new agents targeting the androgen axis

The metabolic functions of androgen receptor (AR) in normal prostate are circumvented in prostate cancer (PCa) to drive tumor growth, and the AR also can acquire new growth-promoting functions during PCa development and progression through genetic and epigenetic mechanisms. Androgen deprivation therapy (ADT, surgical or medical castration) is the standard treatment for metastatic PCa, but patients invariably relapse despite castrate androgen levels (castration-resistant PCa, CRPC). Early studies from many groups had shown that AR was highly expressed and transcriptionally active in CRPC, and indicated that steroids from the adrenal glands were contributing to this AR activity. More recent studies showed that CRPC cells had increased expression of enzymes mediating androgen synthesis from adrenal steroids, and could synthesize androgens de novo from cholesterol. Phase III clinical trials showing a survival advantage in CRPC for treatment with abiraterone (inhibitor of the enzyme CYP17A1 required for androgen synthesis that markedly reduces androgens and precursor steroids) and for enzalutamide (new AR antagonist) have now confirmed that AR activity driven by residual androgens makes a major contribution to CRPC, and led to the recent Food and Drug Administration approval of both agents. Unfortunately, patients treated with these agents for advanced CRPC generally relapse within a year and AR appears to be active in the relapsed tumors, but the molecular mechanisms mediating intrinsic or acquired resistance to these AR-targeted therapies remain to be defined. This review outlines AR functions that contribute to PCa development and progression, the roles of intratumoral androgen synthesis and AR structural alterations in driving AR activity in CRPC, mechanisms of action for abiraterone and enzalutamide, and possible mechanisms of resistance to these agents.

Vitamin D receptor agonist EB1089 is a potent regulator of prostatic "intracrine" metabolism

BACKGROUND

A contributing factor to the emergence of castrate resistant prostate cancer (CRPC) is the ability of the tumor to circumvent low circulating levels of testosterone during androgen deprivation therapy (ADT), through the production of "intracrine" tumoral androgens from precursors including cholesterol and dehydroepiandrosterone (DHEA). As these processes promote AR signaling and prostate cancer progression their modulation is required for disease prevention and treatment.

METHODS

We evaluated the involvement of the vitamin D receptor ligand EB1089 in the regulation of genes with a role in androgen metabolism using the androgen dependent cell lines LNCaP and LAPC-4. EB1089 regulation of androgen metabolism was assessed using QRT-PCR, luciferase promoter assays, western blotting, enzyme activity assays, and LC-MS analyses.

RESULTS

EB1089 induced significant expression of genes involved in androgen metabolism in prostate cancer cells. Real-Time PCR analysis revealed that VDR mediated significant regulation of CYP3A4, CYP3A5, CYP3A43, AKR1C1-3, UGT2B15/17, and HSD17B2. Data revealed potent regulation of CYP3A4 at the level of mRNA, protein expression and enzymatic activity, with VDR identified as the predominant regulator. Inhibition of CYP3A activity using the specific inhibitor ritonavir resulted in alleviation of the anti-proliferative response of VDR ligands in prostate cancer cells. Mass spectrometry revealed that overexpression of CYP3A protein in prostate cancer cells resulted in a significant increase in the oxidative inactivation of testosterone and DHEA to their 6-β-hydroxy-testosterone and 16-α-hydroxy-DHEA metabolites, respectively.

CONCLUSIONS

These data highlight a potential application of VDR-based therapies for the reduction of growth-promoting androgens within the tumor micro-environment.

Characterization of prostate cancer bone metastases according to expression levels of steroidogenic enzymes and androgen receptor splice variants

Background

Intra-tumoral steroidogenesis and constitutive androgen receptor (AR) activity have been associated with castration-resistant prostate cancer (CRPC). This study aimed to examine if CRPC bone metastases expressed higher levels of steroid-converting enzymes than untreated bone metastases. Steroidogenic enzyme levels were also analyzed in relation to expression of constitutively active AR variants (AR-Vs) and to clinical and pathological variables.

Methodology/Principal Findings

Untreated, hormone-naïve (HN, n = 9) and CRPC bone metastases samples (n = 45) were obtained from 54 patients at metastasis surgery. Non-malignant and malignant prostate samples were acquired from 13 prostatectomy specimens. Transcript and protein levels were analyzed by real-time RT-PCR, immunohistochemistry and immunoblotting. No differences in steroidogenic enzyme levels were detected between CRPC and HN bone metastases. Significantly higher levels of SRD5A1, AKR1C2, AKR1C3, and HSD17B10 mRNA were however found in bone metastases than in non-malignant and/or malignant prostate tissue, while the CYP11A1, CYP17A1, HSD3B2, SRD5A2, and HSD17B6 mRNA levels in metastases were significantly lower. A sub-group of metastases expressed very high levels of AKR1C3, which was not due to gene amplification as examined by copy number variation assay. No association was found between AKR1C3 expression and nuclear AR staining, tumor cell proliferation or patient outcome after metastases surgery. With only one exception, high AR-V protein levels were found in bone metastases with low AKR1C3 levels, while metastases with high AKR1C3 levels primarily contained low AR-V levels, indicating distinct mechanisms behind castration-resistance in individual bone metastases.

Conclusions/Significance

Induced capacity of converting adrenal-gland derived steroids into more potent androgens was indicated in a sub-group of PC bone metastases. This was not associated with CRPC but merely with the advanced stage of metastasis. Sub-groups of bone metastases could be identified according to their expression levels of AKR1C3 and AR-Vs, which might be of relevance for patient response to 2^nd line androgen-deprivation therapy.

Intratumoral conversion of adrenal androgen precursors drives androgen receptor-activated cell growth in prostate cancer more potently than de novo steroidogenesis

BACKGROUND

Despite an initial response to hormonal therapy, patients with advanced prostate cancer (PC) almost always progress to castration-resistant disease (CRPC). Although serum testosterone (T) is reduced by androgen deprivation therapy, intratumoral T levels in CRPC are comparable to those in prostate tissue of eugonadal men. These levels could originate from intratumoral conversion of adrenal androgens and/or from de novo steroid synthesis. However, the relative contribution of de novo steroidogenesis to AR-driven cell growth is unknown.

METHODS

The relative contribution of androgen biosynthetic pathways to activate androgen receptor (AR)-regulated cell growth and expression of PSA, FKBP5, and TMPRSS2 was studied at physiologically relevant levels of adrenal androgen precursors and intermediates of de novo androgen biosynthesis in human prostate cancer cell lines, PC346C, VCaP, and LNCaP.

RESULTS

In PC346C and VCaP, responses to pregnenolone and progesterone were absent or minimal, while large effects of adrenal androgen precursors were found. VCaP CRPC clones overexpressing CYP17A1 did not acquire an increased ability to use pregnenolone or progesterone to activate AR. In contrast, all precursors stimulated growth and gene expression in LNCaP cells, presumably resulting from the mutated AR in these cells.

CONCLUSIONS

Our data indicate that at physiological levels of T precursors PC cells can generally convert adrenal androgens, while de novo steroidogenesis is not generally possible in PC cells and is not able to support AR transactivation and PC growth.

Targeting the adrenal gland in castration-resistant prostate cancer: a case for orteronel, a selective CYP-17 17,20-lyase inhibitor

Androgen and the androgen receptor (AR) pathway remain the key targets for emerging new therapies against castration-resistant prostate cancer (CRPC). Adrenal androgens and intratumoral testosterone production appear to be sufficient to activate AR in the castration-resistant setting. This process re-engages AR and allows it to continue to be the primary target responsible for prostate cancer progression. Adrenal androgen production can be blocked by inhibiting cytochrome P450 17α-hydroxylase/17,20-lyase (CYP17), a key enzyme for androgen synthesis in adrenal glands and peripheral tissues. Therapeutic CYP17 inhibition by ketoconazole or by the recently approved adrenal inhibitor abiraterone acetate is the only available choice to target this pathway in CRPC. A new CYP17 inhibitor, with more selective inhibition of 17,20-lyase over 17α-hydroxylase, orteronel (TAK-700), is currently undergoing phase III clinical trials in pre- and postchemotherapy CRPC. In a completed phase II trial in CRPC patients, orteronel demonstrated its efficacy by lowering the levels of circulating androgens, reducing prostate-specific antigen (PSA) levels, and decreasing the levels of circulating tumor cells. Ongoing studies evaluating orteronel in CRPC will further define its safety and role in the management of this disease.

Local endocrine, paracrine and redox signaling networks impact estrogen and androgen crosstalk in the prostate cancer microenvironment

Androgen receptor (AR) signaling is essential for the initial development and progression of prostate cancer (PCa) as well as the growth and survival of castration-resistant tumors. However, AR action may be opposed by estrogen receptor beta (ERß) that responds to androgen metabolites produced in the prostate. The balance between the activity of these two receptors is not only influenced by the steroidogenic capacity of the prostatic microenvironment but also by its redox status and local paracrine signals such as transforming growth factor-beta (TGF-ß). In this review, we highlight the studies that revealed select roles for AR and ERß in distinct compartments of the prostate cancer microenvironment. We also discuss new work that identified stromal-epithelial crosstalk through TGF-ß1 signaling that drives the production of reactive oxygen species in stromal cells thereby selectively limiting the anti-tumor activity of ERß in cancer cells. Therefore, any new therapeutic approaches that seek to limit AR but enhance ERß activity in PCa, must take into account potential adaptive changes in the tumor microenvironment that utilize paracrine signals and altered redox balance to divert local androgen metabolites towards AR at the expense of ERß.

Androgen activates β-catenin signaling in bladder cancer cells

Androgen receptor (AR) signals have been implicated in bladder carcinogenesis and tumor progression. Activation of Wnt/β-catenin signaling has also been reported to correlate with bladder cancer progression and poor patients' outcomes. However, cross talk between AR and β-catenin pathways in bladder cancer remains uncharacterized. In radical cystectomy specimens, we immunohistochemically confirmed aberrant expression of β-catenin especially in aggressive tumors. There was a strong association between nuclear expressions of AR and β-catenin in bladder tumors (P=0.0215). Kaplan-Meier and log-rank tests further revealed that reduced membranous β-catenin expression (P=0.0276), nuclear β-catenin expression (P=0.0802), and co-expression of nuclear AR and β-catenin (P=0.0043) correlated with tumor progression after cystectomy. We then assessed the effects of androgen on β-catenin in AR-positive and AR-negative bladder cancer cell lines. A synthetic androgen R1881 increased the expression of an active form of β-catenin and its downstream target c-myc only in AR-positive lines. R1881 also enhanced the activity of β-catenin-mediated transcription, which was abolished by an AR antagonist hydroxyflutamide. Using western blotting and immunofluorescence, R1881 was found to induce nuclear translocation of β-catenin when co-localized with AR. Finally, co-immunoprecipitation revealed androgen-induced associations of AR with β-catenin or T-cell factor (TCF) in bladder cancer cells. Thus, it was likely that androgen was able to activate β-catenin signaling through the AR pathway in bladder cancer cells. Our results also suggest that activation of β-catenin signaling possibly via formation of AR/β-catenin/TCF complex contributes to the progression of bladder cancer, which may enhance the feasibility of androgen deprivation as a potential therapeutic approach.

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.

Endothelial cells enhance prostate cancer metastasis via IL-6→androgen receptor→TGF-β→MMP-9 signals

Although the potential roles of endothelial cells in the microvascules of prostate cancer during angiogenesis have been documented, their direct impacts on the prostate cancer metastasis remain unclear. We found that the CD31-positive and CD34-positive endothelial cells are increased in prostate cancer compared with the normal tissues and that these endothelial cells were decreased upon castration, gradually recovered with time, and increased after prostate cancer progressed into the castration-resistant stage, suggesting a potential linkage of these endothelial cells with androgen deprivation therapy. The in vitro invasion assays showed that the coculture of endothelial cells with prostate cancer cells significantly enhanced the invasion ability of the prostate cancer cells. Mechanism dissection found that coculture of prostate cancer cells with endothelial cells led to increased interleukin (IL)-6 secretion from endothelial cells, which may result in downregulation of androgen receptor (AR) signaling in prostate cancer cells and then the activation of TGF-β/matrix metalloproteinase-9 (MMP-9) signaling. The consequences of the IL-6→AR→TGFβ→MMP-9 signaling pathway might then trigger the increased invasion of prostate cancer cells. Blocking the IL-6→AR→TGFβ→MMP-9 signaling pathway either by IL-6 antibody, AR-siRNA, or TGF-β1 inhibitor all interrupted the ability of endothelial cells to influence prostate cancer invasion. These results, for the first time, revealed the important roles of endothelial cells within the prostate cancer microenvironment to promote the prostate cancer metastasis and provide new potential targets of IL-6→AR→TGFβ→MMP-9 signals to battle the prostate cancer metastasis.