The antiandrogenic effect of finasteride against a mutant androgen receptor

Acetyl-CoA Counteracts the Inhibitory Effect of Antiandrogens on Androgen Receptor Signaling in Prostate Cancer Cells

The commonly used therapeutic management of PC involves androgen deprivation therapy (ADT) followed by treatment with AR signaling inhibitors (ARSI). However, nearly all patients develop drug-resistant disease, with a median progression-free survival of less than 2 years in chemotherapy-naïve men. Acetyl-coenzyme A (acetyl-CoA) is a central metabolic signaling molecule with key roles in biosynthetic processes and cancer signaling. In signaling, acetyl-CoA serves as the acetyl donor for acetylation, a critical post-translational modification. Acetylation affects the androgen receptor (AR) both directly and indirectly increasing expression of AR dependent genes. Our studies reveal that PC cells respond to the treatment with ARSI by increasing expression of ATP-citrate lyase (ACLY), a major enzyme responsible for cytosolic acetyl-CoA synthesis, and up-regulation of acetyl-CoA intracellular levels. Inhibition of ACLY results in a significant suppression of ligand-dependent and -independent routes of AR activation. Accordingly, the addition of exogenous acetyl-CoA, or its precursor acetate, augments AR transcriptional activity and diminishes the anti-AR activity of ARSI. Taken together, our findings suggest that PC cells respond to antiandrogens by increasing activity of the acetyl-coA pathway in order to reinstate AR signaling.

Ameliorative effect of Abeliophyllum distichum Nakai on benign prostatic hyperplasia in vitro and in vivo

BACKGROUND/OBJECTIVES

Benign prostatic hyperplasia (BPH) is the most common prostate disease and one of the most common chronic diseases caused by aging in men. On the other hand, there has been no research on BPH using Abeliophyllum distichum Nakai (A. distichum). Therefore, this study investigated the effects of A. distichum on BPH.

MATERIALS/METHODS

A. distichum leaves were extracted with distilled water, 70% ethanol, and 95% hexane as solvents. Subsequently, the inhibitory effects of each A. distichum extract on androgen receptor (AR) signaling were evaluated in vitro. The testosterone-induced BPH model was then used to confirm the efficacy of A. distichum leaves in 70% ethanol extract (ADLE).

RESULTS

ADLE had the strongest inhibitory effect on AR signaling. A comparison of the activity of ADLE by harvest time showed that the leaves of A. distichum harvested in autumn had a superior inhibitory effect on AR signaling to those harvested at other times. In the BPH rat model, the administration of ADLE reduced the prostate size and prostate epithelial cell thickness significantly and inhibited AR signaling. Subsequently, the administration of ADLE also reduced the expression of growth factors, thereby inactivating the PI3K/AKT pathway.

CONCLUSIONS

An analysis of the efficacy of ADLE to relieve BPH showed that the ethanol extract grown in autumn exhibited the highest inhibitory ability of the androgen-signaling related factors in vitro. ADLE also inhibited the expression of growth factors by inhibiting the expression of the androgen-signaling related factors in vivo. Overall, ADLE is proposed as a functional food that is effective in preventing BPH.

Proximity-dependent Mapping of the Androgen Receptor Identifies Kruppel-like Factor 4 as a Functional Partner

Prostate cancer (PCa) is the most frequently diagnosed cancer in men and the third cause of cancer mortality. PCa initiation and growth are driven by the androgen receptor (AR). The AR is activated by androgens such as testosterone and controls prostatic cell proliferation and survival. Here, we report an AR signaling network generated using BioID proximity labeling proteomics in androgen-dependent LAPC4 cells. We identified 31 AR-associated proteins in nonstimulated cells. Strikingly, the AR signaling network increased to 182 and 200 proteins, upon 24 h or 72 h of androgenic stimulation, respectively, for a total of 267 nonredundant AR-associated candidates. Among the latter group, we identified 213 proteins that were not previously reported in databases. Many of these new AR-associated proteins are involved in DNA metabolism, RNA processing, and RNA polymerase II transcription. Moreover, we identified 44 transcription factors, including the Kru¨ppel-like factor 4 (KLF4), which were found interacting in androgen-stimulated cells. Interestingly, KLF4 repressed the well-characterized AR-dependent transcription of the KLK3 (PSA) gene; AR and KLF4 also colocalized genome-wide. Taken together, our data report an expanded high-confidence proximity network for AR, which will be instrumental to further dissect the molecular mechanisms underlying androgen signaling in PCa cells.

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BioID proteomics identifies 267 androgen receptor (AR)-associated candidates

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Krüppel-like factor 4 (KLF4) is a new AR interaction partner

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AR and KLF4 colocalize genome-wide on >4000 genes, including KLK3 (PSA)

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KLF4 acts as a repressor for the AR target gene KLK3 (PSA)

Adrenal androgens rescue prostatic dihydrotestosterone production and growth of prostate cancer cells after castration

Adrenal androgens dehydroepiandrosterone (DHEA) and DHEA-sulfate (DHEAS) are potential substrates for intracrine production of testosterone (T) and dihydrotestosterone (DHT), or directly to DHT, by prostate cancer (PCa) cells. Production of DHT from DHEAS and DHEA, and the role of steroid sulfatase (STS), were evaluated ex vivo using fresh human prostate tissue and in vitro using human PCa cell lines. STS was expressed in benign prostate tissue and PCa tissue. DHEAS at a physiological concentration was converted to DHT in prostate tissue and PCa cell lines, which was STS-dependent. DHEAS activation of androgen receptor (AR) and stimulation of PCa cell growth were STS-dependent. DHEA at a physiological concentration was not converted to DHT ex vivo and in vitro, but stimulated in vivo tumor growth of the human PCa cell line, VCaP, in castrated mice. The findings suggest that targeting metabolism of DHEAS and DHEA may enhance androgen deprivation therapy.

An active and selective molecular mechanism mediating the uptake of sex steroids by prostate cancer cells

Steroid hormones play important roles in normal physiological functions and diseases. Sex steroids hormones are important in the biology and treatment of sex hormone-related cancer such as prostate cancer and breast cancer. Cells may take up steroids using multiple mechanisms. The conventionally accepted hypothesis that steroids cross cell membrane through passive diffusion has not been tested rigorously. Experimental data suggested that cells may take up sex steroid using an active uptake mechanism. ³H-testosterone uptake by prostate cancer cells showed typical transporter-mediated uptake kinetic. Cells retained testosterone taken up from the medium. The uptake of testosterone was selective for certain steroid hormones but not others. Data also indicated that the active and selective uptake mechanism resided in cholesterol-rich membrane domains, and may involve ATP and membrane transporters. In summary, the present study provided strong evidence to support the existence of an active and selective molecular mechanism for sex steroid uptake.

Proteomic Analysis of Charcoal-Stripped Fetal Bovine Serum Reveals Changes in the Insulin-like Growth Factor Signaling Pathway

Charcoal-stripped fetal bovine serum (CS-FBS) is commonly used to study androgen responsiveness and androgen metabolism in cultured prostate cancer (CaP) cells. Switching CaP cells from FBS to CS-FBS may reduce the activity of androgen receptor (AR), inhibit cell proliferation, or modulate intracellular androgen metabolism. The removal of proteins by charcoal stripping may cause changes in biological functions and has not yet been investigated. Here we profiled proteins in FBS and CS-FBS using an ion-current-based quantitative platform consisting of reproducible surfactant-aided precipitation/on-pellet digestion, long-column nanoliquid chromatography separation, and ion-current-based analysis. A total of 143 proteins were identified in FBS, among which 14 proteins including insulin-like growth factor 2 (IGF-2) and IGF binding protein (IGFBP)-2 and -6 were reduced in CS-FBS. IGF-1 receptor (IGF1R) and insulin receptor were sensitized to IGFs in CS-FBS. IGF-1 and IGF-2 stimulation fully compensated for the loss of AR activity to maintain cell growth in CS-FBS. Endogenous production of IGF and IGFBPs was verified in CaP cells and clinical CaP specimens. This study provided the most comprehensive protein profiles of FBS and CS-FBS and offered an opportunity to identify new protein regulators and signaling pathways that regulate AR activity, androgen metabolism, and proliferation of CaP cells.

Androgenetic alopecia: a review

PURPOSE

Androgenetic alopecia, commonly known as male pattern baldness, is the most common type of progressive hair loss disorder in men. The aim of this paper is to review recent advances in understanding the pathophysiology and molecular mechanism of androgenetic alopecia.

METHODS

Using the PubMed database, we conducted a systematic review of the literature, selecting studies published from 1916 to 2016.

RESULTS

The occurrence and development of androgenetic alopecia depends on the interaction of endocrine factors and genetic predisposition. Androgenetic alopecia is characterized by progressive hair follicular miniaturization, caused by the actions of androgens on the epithelial cells of genetically susceptible hair follicles in androgen-dependent areas. Although the exact pathogenesis of androgenetic alopecia remains to be clarified, research has shown that it is a polygenetic condition. Numerous studies have unequivocally identified two major genetic risk loci for androgenetic alopecia, on the X-chromosome AR⁄EDA2R locus and the chromosome 20p11 locus.

CONCLUSIONS

Candidate gene and genome-wide association studies have reported that single-nucleotide polymorphisms at different genomic loci are associated with androgenetic alopecia development. A number of genes determine the predisposition for androgenetic alopecia in a polygenic fashion. However, further studies are needed before the specific genetic factors of this polygenic condition can be fully explained.

Peroxiredoxin 1 - an antioxidant enzyme in cancer

Peroxiredoxins (PRDXs), a ubiquitous family of redox‐regulating proteins, are reported of potential to eliminate various reactive oxygen species (ROS). As a major member of the antioxidant enzymes, PRDX1 can become easily over‐oxidized on its catalytically active cysteine induced by a variety of stimuli in vitro and in vivo. In nucleus, oligomeric PRDX1 directly associates with p53 or transcription factors such as c‐Myc, NF‐κB and AR, and thus affects their bioactivities upon gene regulation, which in turn induces or suppresses cell death. Additionally, PRDX1 in cytoplasm has anti‐apoptotic potential through direct or indirect interactions with several ROS‐dependent (redox regulation) effectors, including ASK1, p66^Shc, GSTpi/JNK and c‐Abl kinase. PRDX1 is proven to be a versatile molecule regulating cell growth, differentiation and apoptosis. Recent studies have found that PRDX1 and/or PRDX1‐regulated ROS‐dependent signalling pathways play an important role in the progression and metastasis of human tumours, particularly in breast, oesophageal and lung cancers. In this paper, we review the structure, effector functions of PRDX1, its role in cancer and the pivotal role of ROS in anticancer treatment.

Peroxiredoxin-1 protects estrogen receptor α from oxidative stress-induced suppression and is a protein biomarker of favorable prognosis in breast cancer

INTRODUCTION

Peroxiredoxin-1 (PRDX1) is a multifunctional protein, acting as a hydrogen peroxide (H2O2) scavenger, molecular chaperone and immune modulator. Although differential PRDX1 expression has been described in many tumors, the potential role of PRDX1 in breast cancer remains highly ambiguous. Using a comprehensive antibody-based proteomics approach, we interrogated PRDX1 protein as a putative biomarker in estrogen receptor (ER)-positive breast cancer.

METHODS

An anti-PRDX1 antibody was validated in breast cancer cell lines using immunoblotting, immunohistochemistry and reverse phase protein array (RPPA) technology. PRDX1 protein expression was evaluated in two independent breast cancer cohorts, represented on a screening RPPA (n = 712) and a validation tissue microarray (n = 498). In vitro assays were performed exploring the functional contribution of PRDX1, with oxidative stress conditions mimicked via treatment with H2O2, peroxynitrite, or adenanthin, a PRDX1/2 inhibitor.

RESULTS

In ER-positive cases, high PRDX1 protein expression is a biomarker of improved prognosis across both cohorts. In the validation cohort, high PRDX1 expression was an independent predictor of improved relapse-free survival (hazard ratio (HR) = 0.62, 95% confidence interval (CI) = 0.40 to 0.96, P = 0.032), breast cancer-specific survival (HR = 0.44, 95% CI = 0.24 to 0.79, P = 0.006) and overall survival (HR = 0.61, 95% CI = 0.44 to 0.85, P = 0.004). RPPA screening of cancer signaling proteins showed that ERα protein was upregulated in PRDX1 high tumors. Exogenous H2O2 treatment decreased ERα protein levels in ER-positive cells. PRDX1 knockdown further sensitized cells to H2O2- and peroxynitrite-mediated effects, whilst PRDX1 overexpression protected against this response. Inhibition of PRDX1/2 antioxidant activity with adenanthin dramatically reduced ERα levels in breast cancer cells.

CONCLUSIONS

PRDX1 is shown to be an independent predictor of improved outcomes in ER-positive breast cancer. Through its antioxidant function, PRDX1 may prevent oxidative stress-mediated ERα loss, thereby potentially contributing to maintenance of an ER-positive phenotype in mammary tumors. These results for the first time imply a close connection between biological activity of PRDX1 and regulation of estrogen-mediated signaling in breast cancer.

The direct inhibitory effect of dutasteride or finasteride on androgen receptor activity is cell line specific

BACKGROUND

Finasteride and dutasteride were developed originally as 5α-reductase inhibitors to block the conversion of testosterone to dihydrotestosterone (DHT). These drugs may possess off-target effects on the androgen receptor (AR) due to their structural similarity to DHT.

METHODS

A total of four human prostate cancer cell models were examined: LNCaP (T877A mutant AR), 22Rv1 (H874Y mutant AR), LAPC4 (wild-type AR), and VCaP (wild-type AR). Cells were cultured in 10% charcoal-stripped fetal bovine serum, either with or without DHT added to the medium. AR activity was evaluated using the ARE-luciferase assay or the expression of AR regulated genes.

RESULTS

Dutasteride was more potent than finasteride in interfering with DHT-stimulated AR signaling. Disruption of AR function was accompanied by decreased cell growth. Cells that rely on DHT for protection against death were particularly vulnerable to dutasteride. Different prostate cancer cell models exhibited different sensitivities to dutasteride and finasteride. LNCaP was most sensitive, LAPC4 and VCaP were intermediate, while 22Rv1 was least sensitive. Regardless of the AR genotype, if AR was transfected into drug-sensitive cells, AR was inhibited by drug treatment; and if AR was transfected into drug-resistant cells, AR was not inhibited.

CONCLUSIONS

The direct inhibitory effect of dutasteride or finasteride on AR signaling is cell line specific. Mutations in the ligand binding domain of AR do not appear to play a significant role in influencing the AR antagonistic effect of these drugs. Subcellular constituent is an important factor in determining the drug effect on AR function.

Prostate cancer cells differ in testosterone accumulation, dihydrotestosterone conversion, and androgen receptor signaling response to steroid 5α-reductase inhibitors

BACKGROUND

Blocking 5α-reductase-mediated testosterone conversion to dihydrotestosterone (DHT) with finasteride or dutasteride is the driving hypothesis behind two prostate cancer prevention trials. Factors affecting intracellular androgen levels and the androgen receptor (AR) signaling axis need to be examined systematically in order to fully understand the outcome of interventions using these drugs.

METHODS

The expression of three 5α-reductase isozymes, as determined by immunohistochemistry and qRT-PCR, was studied in five human prostate cancer cell lines. Intracellular testosterone and DHT were analyzed using mass spectrometry. A luciferase reporter assay and AR-regulated genes were used to evaluate the modulation of AR activity.

RESULTS

Prostate cancer cells were capable of accumulating testosterone to a level 15-50 times higher than that in the medium. The profile and expression of 5α-reductase isozymes did not predict the capacity to convert testosterone to DHT. Finasteride and dutasteride were able to depress testosterone uptake in addition to lowering intracellular DHT. The inhibition of AR activity following drug treatment often exceeded the expected response due to reduced availability of DHT. The ability to maintain high intracellular testosterone might compensate for the shortage of DHT.

CONCLUSIONS

The biological effect of finasteride or dutasteride appears to be complex and may depend on the interplay of several factors, which include testosterone turnover, enzymology of DHT production, ability to use testosterone and DHT interchangeably, and propensity of cells for off-target AR inhibitory effect.

Prostate cancer prevention: strategies for agent development

PURPOSE OF REVIEW

This article provides an update of clinical research supported by the National Cancer Institute's Phase I/II prostate cancer chemoprevention agent development program.

RECENT FINDINGS

Numerous clinical trials of pharmacologic interventions to delay, prevent or reverse carcinogenesis ('chemoprevention') with the ultimate goal of reducing cancer incidence have been conducted over the past decade. These trials range from relatively small, short-duration studies with biomarker endpoints to very large, long-term, general population trials with definitive cancer endpoints. Two large, population-based, Phase III prostate cancer prevention trials have shown a significant benefit for 5-α-reductase inhibitors. However, this class of agents was also associated with increased detection of high-grade prostate cancer. Another large, Phase III prostate cancer prevention trial showed no benefit for either selenium or vitamin E, given individually or in combination; in fact, a significant increase in prostate cancer was observed among men randomized to the vitamin E alone arm.

SUMMARY

A number of early phase trials and three definitive Phase III trials have been conducted in the field of prostate cancer prevention over the past decade. Although a great deal has been learned from these studies, significant work remains to be done to fully realize the potential of chemoprevention in this disease.

Anabolic potential of bone mineral in human periosteal fibroblasts using steroid markers of healing

A deproteinized natural cancellous bone mineral (B) was studied in a cell culture model for its anabolic potential using two radiolabelled steroid substrates, 14C-testosterone (14C-T) and 14C-4-androstenedione (14C-4-A) independently; in the presence or absence of the anti-androgen finasteride (F) and minocycline (M). Culture medium was assayed for the biologically active metabolite 5 alpha-dihydrotestosterone (DHT) a marker of regenerative potential and wound healing. Confluent monolayer cultures of human periosteal fibroblasts were incubated in Eagle's minimum essential medium with each of the substrates 14C-T and 14C-4-A. Incubations were performed with previously established optimal concentrations of B5 (milligrams/ml), M25 (μg/ml) and F5 (μg/ml) alone and in combination (n=6) for 24h. The eluent was solvent extracted with ethyl acetate (2 ml x 2) and subjected to TLC in a benzene/acetone solvent system (4:1 v/v) for separation of metabolites; they were quantified using a radioisotope scanner. The yield of DHT was increased over controls in response to B and M with both substrates 14C-T and 14C-4-A by 1.7, 1.8-fold and 1.7, 1.6-fold respectively (n=6; p<0.001; one way ANOVA). Combined incubations of B and M resulted in similar yields. F inhibited DHT yields with both radiolabelled substrates by 2-3-fold (n=6; p<0.001) which was overcome by a combined incubation of F+B to values similar to those of controls (p<0.01). Documented pro-anabolic effects of minocycline were applicable as a standard for confirmation of responses to B. Significant increases in yields of DHT in response to B and M with both substrates indicate their anabolic potential in periosteal fibroblasts with implications for wound healing.

IGF2 increases de novo steroidogenesis in prostate cancer cells

IGF2 is a mitogenic foetal growth factor commonly over-expressed in cancers, including prostate cancer (PC). We recently demonstrated that insulin can activate de novo steroidogenesis in PC cells, a major pathway for reactivation of androgen pathways and PC progression. IGF2 can activate the IGF1 receptor (IGF1R) or insulin receptor (INSR) or hybrids of these two receptors. We therefore hypothesized that IGF2 may contribute to PC progression via de novo steroidogenesis. IGF2 mRNA but not IGF2 receptor mRNA expression was increased in patient samples during progression to castrate-resistant PC as was immunoreactivity to INSR and IGF1R antibodies. Treatment of androgen receptor (AR)-positive PC cell lines LNCaP and 22RV1 with IGF2 for 48 h resulted in increased expression of steroidogenic enzyme mRNA and protein, including steroid acute regulatory protein (StAR), cytochrome p450 family member (CYP)17A1, aldo-keto reductase family member (AKR)1C3 and hydroxysteroid dehydrogenase (HSD)17B3. IGF2 treatment resulted in increased steady state steroid levels and increased de novo steroidogenesis resulting in AR activation as demonstrated by PSA mRNA induction. Inhibition of the IGF1R/INSR signalling axis attenuated the effects of IGF2 on steroid hormone synthesis. We present a potential mechanism for prostatic IGF2 contributing to PC progression by inducing steroidogenesis and that IGF2 signalling and related pathways present attractive targets for PC therapy.

Combination therapy of antiandrogen and XIAP inhibitor for treating advanced prostate cancer

PURPOSE

Overexpression of the androgen receptor (AR) and anti-apoptotic genes including X-linked inhibitor of apoptosis protein (XIAP) provide tumors with a proliferative advantage. Therefore, our objective was to determine whether novel antiandrogen (CBDIV17) and XIAP inhibitor based combination therapy can treat advanced prostate cancer.

METHODS

CBDIV17 and embelin-6g were synthesized and their effect on cell proliferation, apoptosis, cell cycle and AR and XIAP gene silencing determined.

RESULTS

CBDIV17 was more potent than bicalutamide and inhibited proliferation of C4-2 and LNCaP cells, IC(50) for CBDIV17 was ≈ 12 μM and ≈ 21 μM in LNCaP and C4-2 cells, respectively, whereas bicalutamide had IC(50) of ≈ 46 μM in LNCaP cells and minimal effect in C4-2 cells. CBDIV17 induced apoptosis more effectively compared to bicalutamide and significantly inhibited DNA replication. Combination of CBDIV17 and embelin resulted in supra-additive antiproliferative and apoptotic effects. Embelin downregulated AR expression and decreased androgen-mediated AR phosphorylation at Ser(81). These hydrophobic drugs were solubilized using micelles prepared with polyethylene glycol-b-poly (carbonate-co-lactide) (PEG-b-p(CB-co-LA)) copolymer. Combination therapy inhibited prostate tumor growth more effectively compared to control or monotherapy in vivo.

CONCLUSIONS

Our results demonstrated that CBDIV17 in combination with embelin can potentially treat advanced prostate cancer.