Characteristics of the inhibitory effect of chronic treatment with an LHRH agonist on testicular steroidogenesis in the dog

Daily subcutaneous administration for 3 months of the potent LHRH agonist (D-Ser(TBU)6, des-Gly-NH2(10] LHRH ethylamide (25 micrograms) to adult dogs having spontaneous benign prostate hyperplasia (BPH) causes a marked inhibition of testicular androstenedione and testosterone secretion. This inhibition of delta 4-androgen secretion is accompanied by a decrease of testicular progestin precursors and 5 alpha-androgen metabolites, thus suggesting that, in dog, the loss of testicular steroidogenic activity, induced by the administration of an LHRH agonist, is due to a total inhibition of testicular steroidogenesis. In plasma, the concentration of both testosterone and dihydrotestosterone is also markedly depressed while androstane-3 alpha, 17 beta-diol levels remain unchanged. Measurement of prostatic steroid content has shown that administration of the LHRH agonist as well as castration is associated with a marked decrease in androstenedione, testosterone, and dihydrotestosterone levels in prostate while there is a small inhibition of androst-5-ene-3 beta, 17 beta-diol, androstane-3 beta, 17 beta-diol, dehydroepiandrosterone, and estrone concentrations in this tissue. The present data show that treatment with an LHRH agonist in the dog causes a marked inhibition of testicular steroid secretion similar to the one observed in adult men, and suggest that steroids from adrenal origin may also be involved in prostatic function.     

Uptake of resveratrol and role of resveratrol-targeting protein,quinone reductase 2, in normally cultured human prostate cells

Resveratrol is a dietary polyphenol espoused to have chemopreventive activity against a variety of human cancer types. We first reported that resveratrol significantly decreases the proliferation of both androgen-dependent and hormone-refractory prostate cancer cells. However, the effects of resveratrol in normal prostate epithelial and stromal cells, particularly with regard to its uptake, subcellular distribution and intracellular targets, have not been investigated. To advance the knowledge on accessibility and cellular disposition of resveratrol in prostate cells, [3H] resveratrol, fractionation of cell extracts into subcellular compartments, Western blot analysis, resveratrol affinity column chromatography and flow cytometry were used to study the uptake and intracellular distribution of resveratrol in normally cultured prostate stromal （PrSCs） and epithelial cells （PrECs）. Pretreatment of both PrSCs and PrECs for 2 days with resveratrol modulated its uptake and selectively increased its distribution to the membrane and organelle compartments. Resveratrol affinity column chromatography studies showed differential expression of a previously identified resveratrol-targeting protein, quinone reductase 2 （QR2）, in PrSCs and PrECs. Flow cytometric analysis comparing resveratrol-treated and untreated PrSCs showed a large decrease in G1-phase and a concomitant increase in S and G2/M-phases of the cell cycle. These results suggest that resveratrol suppresses PrSC proliferation by affecting cell cycle phase distribution, which may involve the participation by QR2.     

The proliferative effect of estradiol on human prostate stromal cells is mediated through activation of ERK

BACKGROUND: Estrogen is involved in the development and progression of benign prostatic hyperplasia (BPH). It can stimulate proliferation of prostate stromal cells (PrSCs). However, the exact mechanism remains unclear. METHODS: We used the primary cultured human PrSCs and a prostate stromal cell line, WPMY-1, to examine the signaling pathways involved in estrogen-mediated proliferation of PrSCs. Cells were treated with 17beta-estradiol (E(2)) or BSA-E(2). Cell proliferation was assessed by the MTT assay and by cell counting. Western blot analysis was used to determine the status of activation of ERK1/2. RESULTS: Results indicated that both E(2) and BSA-E(2) stimulated proliferation of primary PrSCs and WPMY-1 cells. ERK was rapidly activated by E(2) and BSA-E(2). PD98059, which is a selective ERK inhibitor, significantly inhibited estrogen-induced cell proliferation. PrSCs expressed estrogen receptor alpha (ERalpha) and GPR30 but not ERbeta. Small hairpin RNA (shRNA) to ERalpha, but not to GPR30, blocked estrogen-mediated ERK activation and cell proliferation. CONCLUSIONS: The results indicated that estrogen could activate ERK pathway through the non-genomic ERalpha pathway, leading to proliferation of PrSCs.     

Steroid hormone synthetic pathways in prostate cancer

While androgen deprivation therapy (ADT) remains the primary treatment for metastatic prostate cancer (PCa) since the seminal recognition of the disease as androgen-dependent by Huggins and Hodges in 1941, therapy is uniformly marked by progression to castration-resistant prostate cancer (CRPC) over a period of about 18 months, with an ensuing median survival of 1 to 2 years. Importantly, castration does not eliminate androgens from the prostate tumor microenvironment. Castration resistant tumors are characterized by elevated tumor androgens that are well within the range capable of activating the AR and AR-mediated gene expression, and by steroid enzyme alterations which may potentiate de novo androgen synthesis or utilization of circulating adrenal androgens. The dependence of CRPC on intratumoral androgen metabolism has been modeled in vitro and in vivo, and residual intratumoral androgens are implicated in nearly every mechanism by which AR-mediated signaling promotes castration-resistant disease.These observations suggest that tissue based alterations in steroid metabolism contribute to the development of CRPC and underscore these metabolic pathways as critical targets of therapy. Herein, we review the accumulated body of evidence which strongly supports intracrine (tumoral) androgen synthesis as an important mechanism underlying PCa progression. We first discuss the presence and significance of residual prostate tumor androgens in the progression of CRPC. We review the classical and non-classical pathways of androgen metabolism, and how dysregulated expression of these enzymes is likely to potentiate tumor androgen production in the progression to CRPC. Next we review the in vitro and in vivo data in human tumors, xenografts, and cell line models which demonstrate the capacity of prostate tumors to utilize cholesterol and adrenal androgens in the production of testosterone (T) and dihydrotestosterone (DHT), and briefly review the potential role of exogenous influences on this process. Finally, we discuss the emerging data regarding mechanisms of response and resistance to potent ligand synthesis inhibitors entering clinical practice, and conclude by discussing the implications of these findings for future therapy.     

CYP17 inhibition as a hormonal strategy for prostate cancer

Androgen receptor (AR) signaling has a key role in the pathogenesis of prostate cancer. AR gene amplification, AR overexpression, and activating mutations in the AR occur more frequently as castration-resistant prostate cancer (CRPC) evolves, with intratumoral androgen levels remaining sufficient for AR activation despite castration. The source of these androgens might be either adrenal or intratumoral. AR signaling, therefore, remains a valid treatment target for patients with CRPC. CYP17 is a key enzyme for androgen biosynthesis. The imidazole antifungal agent ketoconazole weakly and nonspecifically inhibits CYP17, but remains unlicensed for this indication. Chemists at the Cancer Research UK Centre for Cancer Therapeutics have designed a novel, selective, irreversible inhibitor of CYP17 called abiraterone, which is more than 20 times more potent than ketoconazole. Abiraterone acetate, a prodrug, has undergone phase I assessment, and is rapidly progressing from phase II to phase III trials, in view of its high level of antitumor activity. This agent is safe and well tolerated, and activity profiles suggest that approximately 50% of CRPC remains AR-ligand driven. Other CYP17 inhibitors with alternative mechanisms of action, for example VN/124-1, are in preclinical development. The rationale for and implications of CYP17 inhibition and the CYP17-targeting agents in development are discussed in this Review.     

去势抵抗性前列腺癌新型内分泌治疗耐药机制研究进展

前列腺癌是男性泌尿生殖系统最常见的恶性肿瘤之一,雄激素在其发生发展中都扮演着重要角色。经去势治疗(ADT)后绝大多数前列腺癌都会进展成为去势抵抗性前列腺癌(CRPC)。肾上腺来源的雄激素和(或)雄激素受体(AR)的改变(包括AR基因扩增)驱动了瘤内雄激素的合成,进而重新雄激素轴信号通路。目前,阿比特龙、恩扎鲁胺等抗雄激素治疗药物都是CRPC患者的一线治疗用药。但是,治疗一段时间后患者仍然会出现耐药和疾病进展。因此,明确CRPC患者抗雄激素治疗耐药机制可以为克服CRPC治疗耐药和改善CRPC患者的预后提供契机。     

Mechanisms of resistance in castration-resistant prostate cancer (CRPC)

Despite advances in prostate cancer diagnosis and management, morbidity from prostate cancer remains high. Approximately 20% of men present with advanced or metastatic disease, while 29,000 men continue to die of prostate cancer each year. Androgen deprivation therapy (ADT) has been the standard of care for initial management of advanced or metastatic prostate cancer since Huggins and Hodges first introduced the concept of androgen-dependence in 1972, but progression to castration-resistant prostate cancer (CRPC) occurs within 2-3 years of initiation of ADT. CRPC, previously defined as hormone-refractory prostate cancer, is now understood to still be androgen dependent. Multiple mechanisms of resistance help contribute to the progression to castration resistant disease, and the androgen receptor (AR) remains an important driver in this progression. These mechanisms include AR amplification and hypersensitivity, AR mutations leading to promiscuity, mutations in coactivators/corepressors, androgen-independent AR activation, and intratumoral and alternative androgen production. More recently, identification of AR variants (ARVs) has been established as another mechanism of progression to CRPC. Docetaxel chemotherapy has historically been the first-line treatment for CRPC, but in recent years, newer agents have been introduced that target some of these mechanisms of resistance, thereby providing additional survival benefit. These include AR signaling inhibitors such as enzalutamide (Xtandi, ENZA, MDV-3100) and CYP17A1 inhibitors such as abiraterone acetate (Zytiga). Ultimately, these agents will also fail to suppress CRPC. While some of the mechanisms by which these agents fail are unique, many share similarities to the mechanisms contributing to CRPC progression. Understanding these mechanisms of resistance to ADT and currently approved CRPC treatments will help guide future research into targeted therapies.     

A narrative review of the role of glucocorticoid receptors in prostate cancer: developments in last 5 years

Background and ObjectiveGlucocorticoids, secreted from the adrenal gland, are commonly used in the treatment of castration-resistant prostate cancer (CRPC) because of their anti-inflammatory and anti-toxic effects. However, glucocorticoids have been reported to have the opposite effects within the course of treatment. Many studies have shown that glucocorticoid receptors (GRs) are involved in the establishment of a dominant population of androgen-independent malignant cells, which may result in CRPC. In this review, we summarized the mechanisms of GRs in CRPC and the clinical application of glucocorticoids based on the present evidence.MethodsWe summarized the isoforms of GRs and the mechanisms involved in CRPC. An updated literature search was performed from the ClinicalTrials database, the National Center for Biotechnology Information database and European Union Drug Regulating Authorities Clinical Trials database. The focus was on the timeframe from 2017 to 2022. At least one primary or secondary outcome [prostate-specific antigen (PSA) response rate, progression-free survival (PFS) or overall survival (OS) and median time to PSA progression] according to studies should be included.Key Content and FindingsThe molecular structures and applications of the isoforms of GR have been intensively researched in the past 60 years. In recent years, researchers have pointed out that GRs may be involved in the development of CRPC via genomic and non-genomic effects. Clinical trials in the past 5 years have focused on the efficacy of drugs regarding CRPC. The use of glucocorticoids during treatments of CRPC follows the guidelines (e.g., NCCN Guidelines^®, guidelines of CSCO, etc.). Based on the collected data, prednisone appears to be the most widely used steroid hormone, followed by dexamethasone. Comparisons of the PSA response rate and the median time to PSA progression revealed that the efficacy of the 2 hormones is similar; however, further research on the effect of steroid hormone in CRPC is still required.ConclusionsVarious GR isoforms may play an important part in the development of CRPC, whose mechanism remains unclear. Most clinical trials have focused on the use of prednisone in the last 5 years. The efficacy of prednisone and dexamethasone is similar.     

Androgen synthesis inhibitors in the treatment of castration-resistant prostate cancer

Suppression of gonadal testosterone synthesis represents the standard first line therapy for treatment of metastatic prostate cancer. However, in the majority of patients who develop castration-resistant prostate cancer （CRPC）, it is possible to detect persistent activation of the androgen receptor （AR） through androgens produced in the adrenal gland or within the tumor itself. Abiraterone acetate was developed as an irreversible inhibitor of the dual functional cytochrome P450 enzyme CYP17 with activity as a 17（~-hydroxylase and 17,20-1yase. CYP17 is necessary for production of nongonadal androgens from cholesterol. Regulatory approval of abiraterone in 2011, based on a phase III trial showing a significant improvement in overall survival （OS） with abiraterone and prednisone versus prednisone, represented proof of principle that targeting AR is essential for improving outcomes in men with CRPC. Inhibition of 17α-hydroxylase by abiraterone results in accumulation of upstream mineralocorticoids due to loss of cortisol-mediated suppression of pituitary adrenocorticotropic hormone （ACTH）, providing a rationale for development of CYP17 inhibitors with increased specificity for 17,20-1yase （orteronel, galeterone and VT-464） that can potentially be administered without exogenous corticosteroids. In this article, we review the development of abiraterone and other CYP17 inhibitors; recent studies with abiraterone that inform our understanding of clinical parameters such as drug effects on quality-of-life, potential early predictors of response, and optimal sequencing of abiraterone with respect to other agents; and results of translational studies providing insights into resistance mechanisms to CYP17 inhibitors leading to clinical trials with drug combinations designed to prolong abiraterone benefit or restore abiraterone activity.     

The expression of xenobiotic-metabolizing enzymes in human prostate and in prostate epithelial cells (PECs) derived from primary cultures

BACKGROUND: Dietary heterocyclic amines (HCAs) are carcinogenic in rodent prostate requiring activation by enzymes such as cytochrome P450 (CYP) and N-acetyltransferase (NAT). METHODS: We investigated by Western blotting and immunohistochemistry the expression of CYP1A1, CYP1A2, and NAT1 in human prostate and in prostate epithelial cells (PECs) derived from primary cultures and tested their ability to activate the dietary carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and its N-hydroxy metabolite (N-OH-IQ) to DNA-damaging moieties. RESULTS: Western blotting identified CYP1A1, CYP1A2, and NAT1. Immunohistochemistry localized NAT1 to the cytoplasm of PECs. Inter-individual variation was observed in the expression levels of CYP1A1, 1A2, and NAT1 (11, 75, and 35-fold, respectively). PECs expressed CYP1A1 and NAT1 but not CYP1A2. When incubated with IQ or N-OH-IQ, PECs formed DNA adducts indicating their ability to metabolically activate these compounds. CONCLUSIONS: Prostate cells possess the capacity to activate dietary carcinogens. PECs may provide a useful model system to study their role in prostate carcinogenesis.     

Key targets of hormonal treatment of prostate cancer. Part 1: the androgen receptor and steroidogenic pathways

OBJECTIVE

Knowledge of the molecular and cellular changes that occur during the transition of hormone‐naïve to castration‐resistant prostate cancer (CRPC) is increasing rapidly. This might provide a window of opportunity for (future) drug development, and for treating patients with these potential devastating states of disease. The objective of this review is to provide an understanding of the mechanisms that prostate cancer cells use to bypass androgen‐deprived conditions.

METHODS

We searched PubMed for experimental and clinical studies that describe the molecular changes that lead to CRPC.

RESULTS

CRPC remains dependent on a functional androgen receptor (AR), AR‐mediated processes, and on the availability of intraprostatic intracellular androgens. CRPCs might acquire different (molecular) mechanisms that enable them to use intracellular androgens more efficiently (AR amplification, AR protein overexpression, AR hypersensitivity), use alternative splice variants of the AR protein to mediate androgen‐independent AR functioning, and have altered co‐activator and co‐repressor gene and protein expression. Furthermore, CRPCs might have the ability to synthesise androgens de novo from available precursors through a renewed and up‐regulated synthesis of steroid‐hormone converting enzymes. Blocking of enzymes key to de novo androgen synthesis could be an alternative means to treat patients with advanced and/or metastatic disease.

CONCLUSION

In CRPC, prostate cancer cells still rely on intracellular androgens and on an active AR for growth and survival. CRPCs have gained mechanisms that enable them to use steroids from the circulation more efficiently through altered gene expression, and through a renewed and up‐regulated synthesis of steroid hormone‐converting enzymes. Additionally, CRPCs might synthesise AR isoforms that enable AR mediated processes independent from available androgens.     

Genetic polymorphisms in CYP17, CYP3A4, CYP19A1, SRD5A2, IGF-1, and IGFBP-3 and prostate cancer risk in African-American men: the Flint Men's Health Study

BACKGROUND: Association studies have examined the significance of several candidate genes based on biological pathways relevant to prostate carcinogenesis, including both the androgen and insulin-like growth factor pathways. Clinical and epidemiologic evidence suggest that androgens, specifically testosterone and dihydrotestosterone (DHT) are important not only in normal prostate growth but in the pathogenesis of prostate cancer. Similarly, the insulin-like growth factor-1 (IGF-1) signaling pathway regulates both cellular proliferation and apoptosis. Therefore, genes involved in the biosynthesis, activation, metabolism and degradation of androgens and the stimulation of mitogenic and antiapoptotic activities of prostate epithelial cells represent important candidates for affecting the development and progression of prostate cancer. METHODS: Using resources from the Flint Men's Health Study, a population-based case control study of African-American men aged 40-79, we evaluated the associations between selected single-nucleotide polymorphisms (SNPs) in the CYP17, CYP3A4, CYP19A1, SDR5A2, IGF1, and IGFBP3 genes and prostate cancer diagnosis in 473 men (131 prostate cancer cases and 342 disease-free controls). RESULTS: We found a significant association between prostate cancer and selected CYP17 SNP genotypes, with the heterozygous genotype conferring decreased risk. Suggestive evidence for association between IGF1 SNPs and prostate cancer were also found. No significant associations were observed between SNPs in the other genes and prostate cancer. CONCLUSIONS: These findings suggest that variation in or around CYP17 and/or IGF1 may be associated with prostate cancer development in the African-American population. Additional studies are needed to determine whether these polymorphisms are indeed associated with prostate cancer risk in African Americans.     

Effect of increasing ratio of estrogen: androgen on proliferation of normal human prostate stromal and epithelial cells, and the malignant cell line LNCaP

BACKGROUND: Changes in steroid ratios seen in the aging male are thought to promote prostate disease. The aims of this study were to compare the effects of varied ratios of steroids on growth of normal stromal and epithelial cell isolates, and the prostate cancer cell line, LNCaP. METHODS: The effect of altered steroid ratios on cell proliferation of normal stromal (PrSC) and epithelial (PrEC) prostate cells, and the malignant cell line, LNCaP, were assessed. RESULTS: Increasing the ratios of both estrogen:dihydrotestosterone (DHT) and DHT:estrogen, stimulated PrSC proliferation, with increasing estrogen:DHT having the greatest effect. LNCaP proliferation was increased significantly by both steroids, but altered ratios had no additional effect. PrEC proliferation was unaffected when cells were grown alone, despite presence of androgen receptors (AR) and estrogen receptors (ER). When grown in co-culture PrEC cell proliferation was significantly increased by treatments. CONCLUSIONS: PrSC proliferation is stimulated by an increasing ratio of estrogen:androgen. Proliferation of normal epithelial cells is stimulated as a result of an indirect action of steroids mediated by stromal cells. Malignant prostate cancer cells have an altered response in comparison.     

Characteristics of separated epithelial and stromal subfractions of prostate: II. Human prostate

Surgical samples of human benign prostatic hyperplasia tissue (BPH) were fractionated into epithelial clumps and stromal fractions, using the "optimal" tissue dissociation procedure developed for rat prostate described in the preceding report. The separated cellular fractions were compared to control unfractionated tissue (wherein extracellular secretory products had been removed) with respect to the concentrations of androgen receptor and enzyme markers on a DNA basis; cell damage was also evaluated by light and electron microscopy (EM). EM revealed extensive cell damage in epithelial clumps and stromal fractions, which had appeared normal when examined by light microscopy. Damage to the ultrastructure of individual epithelial cells present in clump fractions was very variable, involving vacuolization of the cytoplasm and condensation of nuclear chromatin in some cells, vacuolization of just the cytoplasm in other cells; only a small fraction of the cells in clumps had normal ultrastructure. Ultrastructural damage to stromal cells was much greater in fibroblasts than in muscle fibers. The cell damage observed in both subfractions of human prostate was associated with a marked degree of receptor loss. The mean decreases in the number of androgen receptors per unit DNA relative to control unfractionated tissue was 68.5 and 62.5% recovered in epithelial and stromal fractions, respectively. Measurement of various enzymes as "markers" revealed that acid phosphatase activity (per unit DNA) was associated exclusively with the epithelial clump fraction. Prolyl hydroxylase and myosin ATPase activities (per unit DNA) were restricted to the stromal fraction. The limitations of using mechanically separated subfractions of human prostate tissue for evaluation of the cellular distribution or the initial concentration of steroid receptors in human prostate tissue are discussed.