PC-3 cells with enhanced androgen receptor signaling: a model for clonal selection in prostate cancer

RNA-Sequencing Analysis Indicates That N-Cadherin Promotes Prostate Cancer Progression by the Epigenetic Modification of Key Genes

N-cadherin (cadherin-2 [CDH2]) is widely known as the promoter of prostate cancer (PCa) invasion and castration resistance. However, the biological mechanism of N-cadherin in PCa progression is unclear. In this study, we overexpressed N-cadherin in LNCaP cells and downregulated N-cadherin in PC3 cells by lentiviral transduction. Then, differentially expressed genes (DEGs) and dysregulated biological functions were investigated through RNA sequencing (RNA-seq) analyses. We found 13 long noncoding RNA (lncRNA) transcripts, 72 messenger RNA (mRNA) transcripts, and 3 integrated genes were dysregulated by N-cadherin. In the disease enrichment, bone cancer, and neurodegenerative and nervous system diseases were associated with N-cadherin in the circular RNA (circRNA; PC3 versus [vs.,/] LNCaP [PC3/LNCaP] comparison) and DEG analysis (LNCaP_oe_CDH2 vs. LNCaP_oe_NC [LNCaP_oe_CDH2/NC] comparison). Epigenetic reprogramming, such as nucleic acid binding, and chromatin and histone modifications, was enriched in Gene Ontology (GO) analysis (DEGs in LNCaP_oe_CDH2/NC and PC3_sh_NC/CDH2, and host genes of circRNA in PC3/LNCaP). Transcriptional misregulation in cancer, post-translational protein modification, gene expression, and generic transcription pathways were dysregulated in the pathway enrichment analysis (host genes of circRNA in PC3/LNCaP, and DEGs in LNCaP_oe_CDH2/NC and PC3_sh_NC/CDH2). Verifying DEGs through TCGA-PRAD dataset revealed six oncogenes (ARHGEF1, GRAMD1A, GTF2H4, MAPK8IP3, POLD1, and PTBP1) that were commonly upregulated by N-cadherin and in advanced PCa stages. In summary, we identified several oncogenes and biological functions associated with N-cadherin expression in PCa cells. N-cadherin may trigger epigenetic reprogramming in PCa cells to promote tumor progression.

In silico ADMET analysis of the A-, B- and D-modified androstane derivatives with potential anticancer effects

The major challenge in the fight against cancer is to design new drugs that will be more selective for cancer cells, with fewer side effects. Synthetic steroids such as cyproterone, fulvestrant, exemestane and abiraterone are approved powerful drugs for the treatment of hormone-dependent diseases such as breast and prostate cancers. Therefore, androstane derivatives in 17-substituted, 17a-homo lactone and 16,17-seco series, with potent anticancer activity, were selected for pharmacokinetic and druglike predictions from the absorption, distribution, metabolism and excretion (ADME) models. In silico determination of physico-chemical and ADMET properties was performed using SwissADME and ProTox-II web tools. The possibility of gastrointestinal absorption and brain penetration was analyzed using the BOILED-Egg model, while the in silico evaluation of the similarities between selected steroid derivatives and FDA-approved drugs was carried out using the SwissSimilarity tool. Of all tested, two compounds that showed good in silico ADMET results, in addition to promising cytotoxicity and molecular docking results, could potentially be evaluated in in vivo tests.

Anticancer Effects of Propolis Extracts Obtained with the Cold Separation Method on PC-3 and DU-145 Prostate Cancer Cell Lines

Plant extracts are increasingly tested for their biological activity and interactions with neoplastic cells. One of such sources of biologically active substances is propolis. This product has been known for thousands of years and is widely used in alternative, folk medicine. Articles describing its effects on the metabolism and cell signaling pathways of neoplastic cells derived from different organs are also published more and more frequently. The purpose of our study was to evaluate the biological activity of propolis extract produced with the cold separation method into hormone-dependent and hormone-independent prostate cancer cell lines. In our study, the propolis extracts showed at least an inhibitory effect on the growth of PC-3 and DU-145 neoplastic cells. Our results suggest that propolis extracts obtained with the cold separation method may be considered as promising compounds for the production of health-promoting supplements.

Identification of the Regulatory Targets of miR-3687 and miR-4417 in Prostate Cancer Cells Using a Proteomics Approach

MicroRNAs (miRNA) are ubiquitous non-coding RNAs that have a prominent role in cellular regulation. The expression of many miRNAs is often found deregulated in prostate cancer (PCa) and castration-resistant prostate cancer (CRPC). Although their expression can be associated with PCa and CRPC, their functions and regulatory activity in cancer development are poorly understood. In this study, we used different proteomics tools to analyze the activity of hsa-miR-3687-3p (miR-3687) and hsa-miR-4417-3p (miR-4417), two miRNAs upregulated in CRPC. PCa and CRPC cell lines were transfected with miR-3687 or miR-4417 to overexpress the miRNAs. Cell lysates were analyzed using 2D gel electrophoresis and proteins were subsequently identified using mass spectrometry (Maldi-MS/MS). A whole cell lysate, without 2D-gel separation, was analyzed by ESI-MS/MS. The expression of deregulated proteins found across both methods was further investigated using Western blotting. Gene ontology and cellular process network analysis determined that miR-3687 and miR-4417 are involved in diverse regulatory mechanisms that support the CRPC phenotype, including metabolism and inflammation. Moreover, both miRNAs are associated with extracellular vesicles, which point toward a secretory mechanism. The tumor protein D52 isoform 1 (TD52-IF1), which regulates neuroendocrine trans-differentiation, was found to be substantially deregulated in androgen-insensitive cells by both miR-3687 and miR-4417. These findings show that these miRNAs potentially support the CRPC by truncating the TD52-IF1 expression after the onset of androgen resistance.

The roles of RUNX2 and osteoclasts in regulating expression of steroidogenic enzymes in castration-resistant prostate cancer cells

Intratumoral steroidogenesis is involved in development of castration-resistant prostate cancer (CRPC) as bone metastases. The osteoblast transcription factor RUNX2 influences steroidogenesis and is induced in CRPC cells by osteoblasts. This study investigates osteoclastic influence on RUNX2 in intratumoral steroidogenesis. Steroidogenic enzymes and steroid receptors were detected with immunohistochemistry in xenograft intratibial tumors from CRPC cells. In vitro, expression of RUNX2 was increased by osteoclasts in osteoblastic LNCaP-19 cells, but not in osteolytic PC-3. Silencing of RUNX2 downregulates expression of CYP11A1, CYP17A1 and HSD3B1 in LNCaP-19 cells co-cultured with osteoclasts, leading to inhibition of KLK3 expression. Osteoclasts promoted CYP11A1 and RUNX2 promoted AKR1C3, HSD17B3 and CYP19A1, but suppressed ESR2 in PC-3 cells. This study shows that osteoclasts promote RUNX2 regulated induction of key steroidogenic enzymes, influencing activation of androgen receptor in CRPC cells. The potential of RUNX2 as a target to inhibit progression of skeletal metastases of CRPC needs further investigation.

The role of N-cadherin/c-Jun/NDRG1 axis in the progression of prostate cancer

The dysregulation of androgen receptor (AR) signaling is a critical event in the progression of prostate cancer (PCa) and hormone therapy consisting of androgen deprivation (ADT) or AR inhibition is therefore used to treat advanced cases. It is known that N-cadherin becomes upregulated following ADT and can directly induce PCa transformation to the castration-resistant stage (CRPC). However, the relationship between AR and N-cadherin is unclear and may promote better understanding of CRPC pathogenesis and progression. Here, we demonstrate a new axis of N-cadherin/c-Jun/N-myc downstream regulated gene 1 (NDRG1) that N-cadherin promotes c-Jun expression and suppresses NDRG1 to promote invasion and migration of PCa cells through epithelial to mesenchymal transition (EMT). Targeting N-cadherin in combination with enzalutamide (ENZ) treatment synergistically suppressed PC3 cell proliferation in vivo and in vitro. Further studies showed that compared to lower Gleason score (GS) (GS < 7) cases, high GS (GS > 7) cases exhibited elevated N-cadherin expression and reduced NDRG1 expression, corroborating our in vitro observations. We further demonstrate that c-Jun, AR, and DNA methyltransferase-1 (DNMT1) form a complex in the 12-O-tetradecanoyl phorbol-13-acetate (TPA) response elements (TREs) region of the NDRG1 promoter, which suppresses NDRG1 transcription through DNA hypermethylation. In conclusion, we demonstrate an underlying mechanism for how N-cadherin collaborates with AR and NDRG1 to promote CRPC progression. Controlling N-cadherin/c-Jun/NDRG1 axis may help to overcome resistance to commonly used hormone therapy to improve long-term patient outcomes.

Expression and functional role of orphan receptor GPR158 in prostate cancer growth and progression

Prostate cancer (PCa) is the second-leading cause of cancer-related mortality, after lung cancer, in men from developed countries. In its early stages, primary tumor growth is dependent on androgens, thus generally can be controlled by androgen deprivation therapy (ADT). Eventually however, the disease progresses to castration-resistant prostate cancer (CRPC), a lethal form in need of more effective treatments. G-protein coupled receptors (GPCRs) comprise a large clan of cell surface proteins that have been implicated as therapeutic targets in PCa growth and progression. The findings reported here provide intriguing evidence of a role for the newly characterized glutamate family member GPR158 in PCa growth and progression. We found that GPR158 promotes PCa cell proliferation independent of androgen receptor (AR) functionality and that this requires its localization in the nucleus of the cell. This suggests that GPR158 acts by mechanisms different from other GPCRs. GPR158 expression is stimulated by androgens and GPR158 stimulates AR expression, implying a potential to sensitize tumors to low androgen conditions during ADT via a positive feedback loop. Further, we found GPR158 expression correlates with a neuroendocrine (NE) differentiation phenotype and promotes anchorage-independent colony formation implying a role for GPR158 in therapeutic progression and tumor formation. GPR158 expression was increased at the invading front of prostate tumors that formed in the genetically defined conditional Pten knockout mouse model, and co-localized with elevated AR expression in the cell nucleus. Kaplan-Meier analysis on a dataset from the Memorial Sloan Kettering cancer genome portal showed that increased GPR158 expression in tumors is associated with lower disease-free survival. Our findings strongly suggest that pharmaceuticals targeting GPR158 activities could represent a novel and innovative approach to the prevention and management of CRPC.

Hic-5 influences genomic and non-genomic actions of the androgen receptor in prostate myofibroblasts

There is extensive knowledge of androgen receptor (AR) signaling in cancer cells, but less regarding androgen action in stromal cells of the tumor microenvironment. We report here the genome-wide effects of a stromal cell specific molecular adapter and AR coregulator, hydrogen peroxide-inducible gene 5 (Hic-5/TGFB1I1), on AR function in prostate myofibroblasts. Following androgen stimulation, Hic-5 rapidly translocates to the nucleus, coincident with increased phosphorylation of focal adhesion kinase. As a coregulator, Hic-5 acted to amplify or inhibit regulation of approximately 50% of AR target genes, affected androgen regulation of growth, cell adhesion, motility and invasion. These data suggest Hic-5 as a transferable adaptor between focal adhesions and the nucleus of prostate myofibroblasts, where it acts a key mediator of the specificity and sensitivity of AR signaling. We propose a model in which Hic-5 coordinates AR signaling with adhesion and extracellular matrix contacts to regulate cell behavior in the tumor microenvironment.

Molecular and structural basis of androgen receptor responses to dihydrotestosterone, medroxyprogesterone acetate and Δ(4)-tibolone

Medroxyprogesterone acetate (MPA) has widely been used in hormone replacement therapy (HRT), and is associated with an increased risk of breast cancer, possibly due to disruption of androgen receptor (AR) signaling. In contrast, the synthetic HRT Tibolone does not increase breast density, and is rapidly metabolized to estrogenic 3α-OH-tibolone and 3β-OH-tibolone, and a delta-4 isomer (Δ(4)-TIB) that has both androgenic and progestagenic properties. Here, we show that 5α-dihydrotestosterone (DHT) and Δ(4)-TIB, but not MPA, stabilize AR protein levels, initiate specific AR intramolecular interactions critical for AR transcriptional regulation, and increase proliferation of AR positive MDA-MB-453 breast cancer cells. Structural modeling and molecular dynamic simulation indicate that Δ(4)-TIB induces a more stable AR structure than does DHT, and MPA a less stable one. Microarray expression analyses confirms that the molecular actions of Δ(4)-TIB more closely resembles DHT in breast cancer cells than either ligand does to MPA.

Finasteride inhibits human prostate cancer cell invasion through MMP2 and MMP9 downregulation

Introduction

The use of the 5-alpha reductase inhibitors (5-ARIs) finasteride and dutasteride for prostate cancer prevention is still under debate. The FDA recently concluded that the increased prevalence of high-grade tumors among 5-ARI-treated patients must not be neglected, and they decided to disallow the use of 5-ARIs for prostate cancer prevention. This study was conducted to verify the effects of finasteride on prostate cell migration and invasion and the related enzymes/proteins in normal human and tumoral prostatic cell lines.

Materials and Methods

RWPE-1, LNCaP, PC3 and DU145 cells were cultivated to 60% confluence and exposed for different periods to either 10 µM or 50 µM finasteride that was diluted in culture medium. The conditioned media were collected and concentrated, and MMP2 and MMP9 activities and TIMP-1 and TIMP-2 protein expression were determined. Cell viability, migration and invasion were analyzed, and the remaining cell extracts were submitted to androgen receptor (AR) detection by western blotting techniques. Experiments were carried out in triplicate.

Results

Cell viability was not significantly affected by finasteride exposure. Finasteride significantly downregulated MMP2 and MMP9 activities in RWPE-1 and PC3 cells and MMP2 in DU145 cells. TIMP-2 expression in RWPE-1 cells was upregulated after exposure. The cell invasion of all four tested cell lines was inhibited by exposure to 50 µM of finasteride, and migration inhibition only occurred for RWPE-1 and LNCaP cells. AR was expressed by LNCaP, RWPE-1 and PC3 cells.

Conclusions

Although the debate on the higher incidence of high-grade prostate cancer among 5-ARI-treated patients remains, our findings indicate that finasteride may attenuate tumor aggressiveness and invasion, which could vary depending on the androgen responsiveness of a patient’s prostate cells.

Disruption of prostate epithelial differentiation pathways and prostate cancer development

One of the foremost problems in the prostate cancer (PCa) field is the inability to distinguish aggressive from indolent disease, which leads to difficult prognoses and thousands of unnecessary surgeries. This limitation stems from the fact that the mechanisms of tumorigenesis in the prostate are poorly understood. Some genetic alterations are commonly reported in prostate tumors, including upregulation of Myc, fusion of Ets genes to androgen-regulated promoters, and loss of Pten. However, the specific roles of these aberrations in tumor initiation and progression are poorly understood. Likewise, the cell of origin for PCa remains controversial and may be linked to the aggressive potential of the tumor. One important clue is that prostate tumors co-express basal and luminal protein markers that are restricted to their distinct cell types in normal tissue. Prostate epithelium contains layer-specific stem cells as well as rare bipotent cells, which can differentiate into basal or luminal cells. We hypothesize that the primary oncogenic cell of origin is a transient-differentiating bipotent cell. Such a cell must maintain tight temporal and spatial control of differentiation pathways, thus increasing its susceptibility for oncogenic disruption. In support of this hypothesis, many of the pathways known to be involved in prostate differentiation can be linked to genes commonly altered in PCa. In this article, we review what is known about important differentiation pathways (Myc, p38MAPK, Notch, PI3K/Pten) in the prostate and how their misregulation could lead to oncogenesis. Better understanding of normal differentiation will offer new insights into tumor initiation and may help explain the functional significance of common genetic alterations seen in PCa. Additionally, this understanding could lead to new methods for classifying prostate tumors based on their differentiation status and may aid in identifying more aggressive tumors.

A novel histone deacetylase (HDAC) inhibitor MHY219 induces apoptosis via up-regulation of androgen receptor expression in human prostate cancer cells

Histone deacetylase (HDAC) inhibitors are a new class of anticancer agents that act by inhibiting cancer cell proliferation and inducing apoptosis in various cancer cell lines. To investigate the anticancer effect of a novel histone deacetylase (HDAC) inhibitor MHY219, its efficacy was compared to that of suberoylanilide hydroxamic acid (SAHA) in human prostate cancer cells. The anticancer effects of MHY219 on cell viability, HDAC enzyme activity, cell cycle regulation, apoptosis and other biological assays were performed. MHY219 was shown to enhance the cytotoxicity on DU145 cells (IC₅₀, 0.36 μM) when compared with LNCaP (IC₅₀, 0.97 μM) and PC3 cells (IC₅₀, 5.12 μM). MHY219 showed a potent inhibition of total HDAC activity when compared with SAHA. MHY219 increased histone H3 hyperacetylation and reduced the expression of class I HDACs (1, 2 and 3) in prostate cancer cells. MHY219 effectively increased the sub-G1 fraction of cells through p21 and p27 dependent pathways in DU145 cells. MHY219 significantly induced a G2/M phase arrest in DU145 and PC3 cells and arrested the cell cycle at G0/G1 phase in LNCaP cells. Furthermore, MHY219 effectively increased apoptosis in DU145 and LNCaP cells, but not PC3 cells, according to Annexin V/PI staining and Western blot analysis. These results indicate that MHY219 is a potent HDAC inhibitor that targets regulating multiple aspects of cancer cell death and might have preclinical value in human prostate cancer chemotherapy, warranting further investigation.

Functional characterization and molecular expression of large neutral amino acid transporter (LAT1) in human prostate cancer cells

The primary objective of this study is to functionally characterize and provide molecular evidence of large neutral amino acid transporter (LAT1) in human derived prostate cancer cells (PC-3). We carried out the uptake of [3H]-tyrosine to assess the functional activity of LAT1. Reverse transcription-polymerase chain reaction (RT-PCR) analysis is carried out to confirm the molecular expression of LAT1. [3H]-tyrosine uptake is found to be time dependent and linear up to 60 min. The uptake process does not exhibit any dependence on sodium ions, pH and energy. However, it is temperature dependent and found maximal at physiological temperature. The uptake of [3H]-tyrosine demonstrates saturable kinetics with K(m) and V(max) values of 34 ± 3 μM and 0.70 ± 0.02 nanomoles/min/mg protein, respectively. It is strongly inhibited by large neutral (phenylalanine, tryptophan, leucine, isoleucine) and small neutral (alanine, serine, cysteine) but not by basic (lysine and arginine) and acidic (aspartic and glutamic acid) amino acids. Isoleucine-quinidine (Ile-quinidine) prodrug generates a significant inhibitory effect on [3H]-tyrosine uptake suggesting that it is recognized by LAT1. RT-PCR analysis provided a product band at 658 and 840 bp, specific to LAT1 and LAT2, respectively. For the first time, this study demonstrates that LAT1, primarily responsible for the uptake of large neutral amino acids, is functionally active in PC-3 cells. Significant increase in the uptake generated by Ile-quinidine relative to quinidine suggests that LAT1 can be utilized for enhancing the cellular permeation of poor cell permeable anticancer drugs. Furthermore, this cell line can be utilized as an excellent in vitro model for studying the interaction of large neutral amino acid conjugated drugs with LAT1 transporter.

PCA3 noncoding RNA is involved in the control of prostate-cancer cell survival and modulates androgen receptor signaling

BACKGROUND

PCA3 is a non-coding RNA (ncRNA) that is highly expressed in prostate cancer (PCa) cells, but its functional role is unknown. To investigate its putative function in PCa biology, we used gene expression knockdown by small interference RNA, and also analyzed its involvement in androgen receptor (AR) signaling.

METHODS

LNCaP and PC3 cells were used as in vitro models for these functional assays, and three different siRNA sequences were specifically designed to target PCA3 exon 4. Transfected cells were analyzed by real-time qRT-PCR and cell growth, viability, and apoptosis assays. Associations between PCA3 and the androgen-receptor (AR) signaling pathway were investigated by treating LNCaP cells with 100 nM dihydrotestosterone (DHT) and with its antagonist (flutamide), and analyzing the expression of some AR-modulated genes (TMPRSS2, NDRG1, GREB1, PSA, AR, FGF8, CdK1, CdK2 and PMEPA1). PCA3 expression levels were investigated in different cell compartments by using differential centrifugation and qRT-PCR.

RESULTS

LNCaP siPCA3-transfected cells significantly inhibited cell growth and viability, and increased the proportion of cells in the sub G0/G1 phase of the cell cycle and the percentage of pyknotic nuclei, compared to those transfected with scramble siRNA (siSCr)-transfected cells. DHT-treated LNCaP cells induced a significant upregulation of PCA3 expression, which was reversed by flutamide. In siPCA3/LNCaP-transfected cells, the expression of AR target genes was downregulated compared to siSCr-transfected cells. The siPCA3 transfection also counteracted DHT stimulatory effects on the AR signaling cascade, significantly downregulating expression of the AR target gene. Analysis of PCA3 expression in different cell compartments provided evidence that the main functional roles of PCA3 occur in the nuclei and microsomal cell fractions.

CONCLUSIONS

Our findings suggest that the ncRNA PCA3 is involved in the control of PCa cell survival, in part through modulating AR signaling, which may raise new possibilities of using PCA3 knockdown as an additional therapeutic strategy for PCa control.

Subdomain structure of the co-chaperone SGTA and activity of its androgen receptor client

Ligand-dependent activity of steroid receptors is affected by tetratricopeptide repeat (TPR)-containing co-chaperones, such as small glutamine-rich tetratricopeptide repeat-containing alpha (SGTA). However, the precise mechanisms by which the predominantly cytoplasmic TPR proteins affect downstream transcriptional outcomes of steroid signaling remain unclear. In this study, we assessed how SGTA affects ligand sensitivity and action of the androgen receptor (AR) using a transactivation profiling approach. Deletion mapping coupled with structural prediction, transcriptional assays, and in vivo regulation of AR-responsive promoters were used to assess the role of SGTA domains in AR responses. At subsaturating ligand concentrations of ≤ 0.1 nM 5α-dihydrotestosterone, SGTA overexpression constricted AR activity by an average of 32% (P<0.002) across the majority of androgen-responsive loci tested, as well as on endogenous promoters in vivo. The strength of the SGTA effect was associated with the presence or absence of bioinformatically predicated transcription factor motifs at each site. Homodimerizaion of SGTA, which is thought to be necessary for chaperone complex formation, was found to be dependent on the structural integrity of amino acids 1-80, and a core evolutionary conserved peptide within this region (amino acids 21-40) necessary for an effect of SGTA on the activity of both exogenous and endogenous AR. This study provides new insights into the subdomain structure of SGTA and how SGTA acts as a regulator of AR ligand sensitivity. A change in AR:SGTA ratio will impact the cellular and molecular response of prostate cancer cells to maintain androgenic signals, which may influence tumor progression.

Corepressor effect on androgen receptor activity varies with the length of the CAG encoded polyglutamine repeat and is dependent on receptor/corepressor ratio in prostate cancer cells

The response of prostate cells to androgens reflects a combination of androgen receptor (AR) transactivation and transrepression, but how these two processes differ mechanistically and influence prostate cancer risk and disease outcome remain elusive. Given recent interest in targeting AR transrepressive processes, a better understanding of AR/corepressor interaction and responses is warranted. Here, we used transactivation and interaction assays with wild-type and mutant ARs, and deletion AR fragments, to dissect the relationship between AR and the corepressor, silencing mediator for retinoic acid and thyroid hormone receptors (SMRT). We additionally tested how these processes are influenced by AR agonist and antagonist ligands, as well as by variation in the polyglutamine tract in the AR amino terminal domain (NTD), which is encoded by a polymorphic CAG repeat in the gene. SMRT was recruited to the AR ligand binding domain by agonist ligand, and as determined by the effect of strategic mutations in activation function 2 (AF-2), requires a precise conformation of that domain. A distinct region of SMRT also mediated interaction with the AR-NTD via the transactivation unit 5 (TAU5; residues 315-538) region. The degree to which SMRT was able to repress AR increased from 17% to 56% as the AR polyglutamine repeat length was increased from 9 to 42 residues, but critically this effect could be abolished by increasing the SMRT:AR molar ratio. These data suggest that the extent to which the CAG encoded polyglutamine repeat influences AR activity represents a balance between corepressor and coactivator occupancy of the same ligand-dependent and independent AR interaction surfaces. Changes in the homeostatic relationship of AR to these molecules, including SMRT, may explain the variable penetrance of the CAG repeat and the loss of AR signaling flexibility in prostate cancer progression.

Serum testosterone bioassay evaluation in a large male cohort

OBJECTIVE

To assess if a cell-based readout of androgen action in serum demonstrates a closer association with recognized classical parameters of androgen action in men than current measures of serum testosterone (T).

DESIGN

To develop, validate and utilize a mammalian cell-based assay to measure specifically bioactive T and determine if this measure is a physiologically relevant fraction of serum T. MEASUREMENTS AND PARTICIPANTS: We have developed a specific serum T bioassay using human prostate cancer cells. A rapid 5-min exposure to 100% serum followed by serum withdrawal confers specificity of the assay to serum T and provides sufficient sensitivity to measure T in male serum samples. Matrix effects were experimentally discounted as a confounding issue. A total of 960 male serum samples from the Florey Adelaide Male Ageing Study (FAMAS) with previous comprehensive cohort data and serum measurements were utilized.

RESULTS

Bioassay T measurement in the 960 FAMAS serum samples returned a median of 10.7 nmol/l (1.7-45.4), and was most closely related to immunoassayed total T, but not immunoassayed bioavailable T or calculated free T. Immunoassayed total T demonstrated a positive association with isometric grip-strength (R(2) = 0.127, P < 0.001), self-reported sexual desire (R(2) = 0.113, P < 0.001) and erectile function (R(2) = 0.085, P < 0.05) while bioassay T did not.

CONCLUSIONS

While cellular bioassays offer a rapid and sensitive means of identifying the androgenic potential of complex environmental compounds, the utility of such assays in defining a clinically relevant fraction of serum T distinct from total T needs further investigation.

Functional enhancers at the gene-poor 8q24 cancer-linked locus

Multiple discrete regions at 8q24 were recently shown to contain alleles that predispose to many cancers including prostate, breast, and colon. These regions are far from any annotated gene and their biological activities have been unknown. Here we profiled a 5-megabase chromatin segment encompassing all the risk regions for RNA expression, histone modifications, and locations occupied by RNA polymerase II and androgen receptor (AR). This led to the identification of several transcriptional enhancers, which were verified using reporter assays. Two enhancers in one risk region were occupied by AR and responded to androgen treatment; one contained a single nucleotide polymorphism (rs11986220) that resides within a FoxA1 binding site, with the prostate cancer risk allele facilitating both stronger FoxA1 binding and stronger androgen responsiveness. The study reported here exemplifies an approach that may be applied to any risk-associated allele in non-protein coding regions as it emerges from genome-wide association studies to better understand the genetic predisposition of complex diseases.

Genome-wide scans of inherited genetic variation in the normal population have recently identified many sites (loci) associated with the predisposition to complex diseases such as cancer. Some of these cancer-associated loci, however, are devoid of genes (situated in so-called “gene deserts”) and the mechanism(s) of the association are not readily apparent. In the work reported here, we show that loci associated with several cancers in a gene desert found at chromosomal area 8q24 have embedded regulatory sequences affecting gene expression as enhancers, and in one case this activity is modulated by genetic variation. The results provide insight into the mechanism(s) governing genetic cancer risk.

A novel androgen receptor amino terminal region reveals two classes of amino/carboxyl interaction-deficient variants with divergent capacity to activate responsive sites in chromatin

The androgen receptor (AR) is an important signaling molecule in multiple tissues, yet its mode of action and cell-specific activities remain enigmatic. AR function has been best studied in the prostate, in which it is essential for growth and homeostasis of the normal organ as well as each stage of cancer development. Investigation of mechanisms responsible for continued AR action that evolve during prostate cancer progression or after hormonal management of the disease have been instructive in defining AR signaling pathways. In the current paper, we use sequence similarity and the collocation of somatic mutations in prostate cancer to define residues 501-535 of the AR amino-terminal domain as an important mediator of receptor function. Specifically, the 501-535 region is required for optimal interaction of the amino-terminal domain with both the p160 coactivator, nuclear receptor coactivator-2, and the AR-ligand binding domain in the amino/carboxyl (N/C) interaction. The N/C interaction is decreased by deletion of the 501-535 region but is distinct from deletion of the (23)FQNLF(27) peptide in that it does not affect the capacity of the AR to activate transcription from a chromatin integrated reporter or recruitment of the receptor to androgen-responsive loci in vivo. Collectively, we have been able to outline two classes of N/C-deficient AR variant that are divergent in their capacity to act in a chromatin context, thereby further defining the interplay between N/C interaction and coregulator recruitment via multiple receptor domains. These mechanisms are likely to be key determinants of the cell and promoter specific activities of the AR.

Repression of Runx2 by androgen receptor (AR) in osteoblasts and prostate cancer cells: AR binds Runx2 and abrogates its recruitment to DNA

Runx2 and androgen receptor (AR) are master transcription factors with pivotal roles in bone metabolism and prostate cancer (PCa). We dissected AR-mediated repression of Runx2 in dihydrotestosterone (DHT)-treated osteoblastic and PCa cells using reporter assays and endogenous Runx2 target genes. Repression required DHT, but not AR's transactivation function, and was associated with nuclear colocalization of the two proteins. Runx2 and AR coimmunoprecipitated and interacted directly in glutathione-S-transferase pull-down assays. Interaction was ionic in nature. Intact AR DNA-binding domain (DBD) was necessary and sufficient for both interaction with Runx2 and its repression. Runx2 sequences required for interaction were the C-terminal 132 amino acid residues together with the Runt DBD. Runx2 DNA binding was abrogated by endogenous AR in chromatin immunoprecipitation assays and by recombinant AR-DBD in gel shift assays. Furthermore, AR caused increased nuclear mobility of Runx2 as indicated by faster fluorescence recovery after photobleaching. Thus, AR binds Runx2 and abrogates its binding to DNA and possibly to other nuclear components. Clinical relevance of our results was suggested by an inverse correlation between expression of AR-responsive prostate-specific antigen and osteocalcin genes in PCa biopsies. Given the tumor suppressor properties of Runx2, its repression by AR may constitute a mechanism of hormone carcinogenesis. Attenuation of Runx2 by AR in osteoblasts may play a role in skeletal metabolism: the bone-sparing effect of androgens is attributable, in part, to keeping Runx2 activity in check and preventing high-turnover bone disease such as seen after castration and in transgenic mice overexpressing Runx2 in osteoblasts.

Androgen-mediated cholesterol metabolism in LNCaP and PC-3 cell lines is regulated through two different isoforms of acyl-coenzyme A:Cholesterol Acyltransferase (ACAT)

BACKGROUND

The objective of this work was to determine the effect of an androgen agonist, R1881, on intracellular cholesterol synthesis and esterification in androgen-sensitive (AS) prostate cancer (LNCaP) cells.

METHODS

We investigated the activity and expression of cholesterol metabolism enzymes, HMG-CoA-reductase and ACAT in the LNCaP and PC-3 (androgen-independent control) models.

RESULTS

Microsomal PC-3 HMG-CoA-reductase activity was increased with R1881 despite having similar cholesterol levels while increased cholesterol levels in microsomes from LNCaPs treated with R1881 (L+) were associated with increased HMG-CoA reductase activity. Increased intracellular cholesteryl esters (CE) found in (L+) were not associated with an increased ACAT1 activity. There was no effect from androgen treatment on ACAT1 protein expression in theses cells; however, ACAT2 expression was induced upon R1881 treatment. In contrast, we found an increase in the in vitro ACAT1 activity in PC-3 cells treated with androgen (P+). Only ACAT1 expression was induced in P+. We further assessed the expression of STAT1 alpha, a transcriptional activator that modulates ACAT1 expression. STAT1 alpha expression and phosphorylation were induced in P+. To determine the role of the AR on ACAT1 expression and esterification, we treated PC-3 cells overexpressing the androgen receptor with R1881 (PAR+). AR expression was decreased in PAR+ cells; ACAT1 protein expression and cholesterol ester levels were also decreased, however, ACAT2 remained unchanged. STAT1 alpha expression was decreased in PAR+.

CONCLUSIONS

Overall, these findings support the importance of cholesterol metabolism regulation within prostate cancer cells and unravel a novel role for STAT1 alpha in prostate cancer metabolism.

Androgen decreases osteoprotegerin expression in prostate cancer cells

Osteoprotegerin (OPG), a key regulator of bone resorption, is hypothesized to have a role in prostate cancer (CaP) bone metastasis. As advanced CaP is treated by androgen ablation, we examined if androgen modulates OPG expression by CaP cell lines in vitro. Basal levels of secreted OPG protein were significantly greater in androgen-independent PC-3 cells compared with androgen-responsive LNCaP-FGC cells (P<0.001); OPG was not detected in the androgen-responsive CaP cell lines LAPC-4 or DuCaP. Treatment with 5alpha-dihydrotestosterone (5alpha-DHT) significantly decreased OPG protein levels in both PC-3 and LNCaP-FGC, with maximal suppression using 10(-9)-10(-7) M 5alpha-DHT in PC-3 (P<0.01; day 3), and using 10(-10)-10(-9) M 5alpha-DHT in LNCaP-FGC cells (P<0.01; day 6). OPG messenger RNA levels were not significantly altered by this 5alpha-DHT treatment. Co-treatment with 10(-6) M flutamide blocked 5alpha-DHT inhibition of OPG protein expression in LNCaP-FGC cells. These data suggest that androgen may modulate OPG protein levels in CaP cell lines in vitro using a post-transcriptional mechanism.

Suppression of Androgen Receptor Signaling in Prostate Cancer Cells by an Inhibitory Receptor Variant

There is increasing evidence that sensitization of the androgen receptor (AR) signaling pathway contributes to the failure of androgen ablation therapy for prostate cancer, and that direct targeting of the AR may be a useful therapeutic approach. To better understand how AR function could be abrogated in prostate cancer cells, we have developed a series of putative dominant-negative variants of the human AR, containing deletions or mutations in activation functions AF-1, AF-5, and/or AF-2. One construct, AR inhibitor (ARi)-410, containing a deletion of AF-1 and part of AF-5 of the AR, had no intrinsic transactivation activity but inhibited wild-type AR (wtAR) in a ligand-dependent manner by at least 95% when transfected at a 4:1 molar ratio. ARi-410 was an equally potent inhibitor of gain-of-function AR variants. Ectopic expression of ARi-410 inhibited the proliferation of AR-positive LNCaP cells, but not AR-negative PC-3 cells. Whereas ARi-410 also marginally inhibited progesterone receptor activity, this was far less pronounced than the effect on AR (50% vs. 95% maximal inhibition, respectively), and there was no inhibition of either vitamin D or estrogen receptor activity. In the presence of ligand, ARi-410 interacted with wtAR, and both receptors translocated into the nucleus. Whereas the amino-carboxy terminal interaction was not necessary for optimal dominant-negative activity, disruption of dimerization through the ligand binding domain reduced the efficacy of ARi-410. In addition, although inhibition of AR function by ARi-410 was not dependent on DNA binding, the DNA binding domain was required for dominant-negative activity. Taken together, our results suggest that interaction between ARi-410 and the endogenous AR in prostate cancer cells, potentially through the DNA binding and ligand binding domains, results in a functionally significant reduction in AR signaling and AR-dependent cell growth.

DU-145 and PC-3 human prostate cancer cell lines express androgen receptor: Implications for the androgen receptor functions and regulation

The majority of human prostate cancer cell lines, including the two "classical" cell lines DU-145 and PC-3, are reported to be androgen receptor (AR)-negative. However, other studies have provided evidence that the DU-145 and PC-3 cell lines express AR mRNA. These contradictory observations prompted us to investigate whether DU-145 and PC-3 cell lines express the androgen receptor. Using antipeptide antibodies directed against three distinct regions of the human AR protein and an improved method to detect AR protein in immunoblotting, we report that DU-145 and PC-3 cell lines express AR protein. We found that the relative levels of the AR mRNA and protein that were detected in DU-145 and PC-3 cell lines were lower than the LNCaP, an AR-positive cell line. Moreover, the antibody directed against the non-variant region (amino acids 299-315), but not the variant N- or C-terminal region (amino acids 1-20 and 900-919, respectively) of the human AR protein, detected the expression of AR in all prostate cancer cell lines. Notably, treatment of these cell lines with dihydrotestosterone (DHT) resulted in measurable increases in the AR protein levels and considerable nuclear accumulation. Although, treatment of DU-145 and PC-3 cells with DHT did not result in stimulation of the activity of an AR-responsive reporter, knockdown of AR expression in PC-3 cells resulted in decreases in p21(CIP1) protein levels, and a measurable decrease in the activity of the p21-luc-reporter. Our observations demonstrate the expression of AR protein in DU-145 and PC-3 prostate cancer cell lines.

Characterization of the TSU-PR1 cell line by chromosome painting and flow cytometry

TSU-PR1 was originally reported as a prostatic carcinoma cell line derived from a lymph node metastasis. Recently, however, this cell line was reported to be derived from T24 bladder carcinoma cells, and thus further definition of its origin is needed. Conventional cytogenetic study of TSU-PR1 showed aneuploidy, ranging from 65 to 86 chromosome with a modal number of 80, and with 10 marker chromosomes, thus conventional cytogenetics cannot be used to determine which chromosomes or regions of chromosomes are critical in cancer development and progression of this cell line. The present study was conducted to characterize genetic changes of the cell line using comparative genomic hybridization (CGH), fluorescence in situ hybridization (FISH), and flow cytometry. CGH results showed that green-to-red fluorescence ratios were within the range of 0.85-1.15, except for a few chromosomes, which reflected near tetraploidy in TSU-PR1. Flow cytometric analysis of TSU-PR1 revealed a DNA index of 3.46n, which is close to the 3.48n calculated from a modal number of 80. The copy numbers of chromosomes 4, 6, 7, 17, and 20 determined by the DNA index and the CGH analyses were 2.85 +/- 0.09, 3.22 +/- 0.77, 3.01 +/- 0.26, 4.05 +/- 0.44, and 4.99 +/- 0.48, respectively. These numbers are also in accordance with the chromosome copy numbers determined with FISH: 2.98 +/- 0.23, 2.91 +/- 0.44, 2.74 +/- 0.44, 3.93 +/- 0.38, and 5.05 +/- 0.78 for chromosomes 4, 6, 7, 17, and 20, respectively (P > 0.05).

Vav3, a Rho GTPase guanine nucleotide exchange factor, increases during progression to androgen independence in prostate cancer cells and potentiates androgen receptor transcriptional activity

The progression of prostate cancer from androgen dependence to androgen independence is often accompanied by enhanced androgen receptor (AR) transcriptional activity. We observed a marked increase in the expression of Vav3, a Rho GTPase guanine nucleotide exchange factor (GEF), during the progression of human prostate cancer LNCaP cells to the androgen-independent derivative, LNCaP-R1. GEFs activate Rho family GTPases by promoting the exchange of GDP for GTP. Reporter gene assays showed that Vav3 potentiated AR transcriptional activity, and knock down of Vav3 resulted in decreased AR transactivation. Vav3 also increased androgen-induced levels of prostate-specific antigen mRNA. Furthermore, Vav3 enhanced AR activity at subnanomolar concentrations of androgen. This finding is particularly relevant because low androgen levels may be present in prostate tissue of patients undergoing androgen deprivation therapy. Enhancement of AR activity by Vav3 required amino terminal activation function 1 (AF1) of AR; however, Vav3 did not interact with AR or increase AR levels. Neither GEF function nor the C-terminal domains of Vav3 were required for Vav3-mediated enhancement of AR activity; however, the pleckstrin homology domain was obligatory. These data show that Vav3 levels rise during progression to androgen independence and support continued AR signaling (even under conditions of low androgen) by a novel GEF-independent cross-talk mechanism.

Decreased Androgen Receptor Levels and Receptor Function in Breast Cancer Contribute to the Failure of Response to Medroxyprogesterone Acetate

Previously, we reported that androgen receptor (AR), but not estrogen receptor (ER) or progesterone receptor (PR), is predictive of response to the synthetic progestin, medroxyprogesterone acetate (MPA), in a cohort of 83 patients with metastatic breast cancer. To further investigate the role of AR in determining response to MPA in this cohort, we analyzed AR levels by immunohistochemistry with two discrete antisera directed at either the NH2 or the COOH termini of the receptor. Compared with tumors that responded to MPA (n = 31), there was a significant decrease in the intensity and extent of AR immunoreactivity with both AR antisera in tumors from nonresponders (n = 52). Whereas only a single AR immunostaining pattern was detected in responders to MPA, reflecting concordance of immunoreactivity with the two AR antisera, tumors from nonresponders exhibited four distinct AR immunostaining patterns: (a) concordance with the two antibodies (31%), (b) staining only with the COOH-terminal antibody (33%), (c) staining only with the NH2-terminal antibody (22%), or (d) no immunoreactivity with either NH2- or COOH-terminal antibody (14%). DNA sequencing and functional analysis identified inactivating missense gene mutations in the ligand-binding domain of the AR in tumors from two of nine nonresponders positive with the NH2-terminal AR antisera but negative for COOH-terminal immunoreactivity and lacking specific, high-affinity dihydrotestosterone binding in tumor cytosol fractions. Tumors with more AR than the median level (37 fmol/mg protein) had significantly lower levels of PR (30 fmol/mg protein) than tumors with low AR (PR; 127 fmol/mg protein) despite comparable levels of ER. Ligand-dependent activation of the AR in human T47D and MCF-7 breast cancer cells resulted in inhibition of estradiol-stimulated cell proliferation and a reduction in the capacity of the ER to induce expression of the PR. These effects could be reversed using a specific AR antisense oligonucleotide. Increasing the ratio of AR to ER resulted in a greater androgen-dependent inhibition of ER function. Collectively, these data suggest that reduced levels of AR or impaired AR function contribute to the failure of MPA therapy potentially due to abrogation of the inhibitory effect of AR on ER signaling.