Transcriptome Analysis of Choroidal Endothelium Links Androgen Receptor Role to Central Serous Chorioretinopathy

BACKGROUND

Central Serous Chorioretinopathy (CSCR) manifests as fluid accumulation between the neurosensory retina and the retinal pigment epithelium (RPE). Elevated levels of steroid hormones have been implicated in CSCR pathogenesis. This investigation aims to delineate the gene expression patterns of CSCR-associated risk and steroid receptors across human choroidal cell types and RPE cells to discern potential underlying mechanisms.

METHODS

This study utilized a comprehensive query of transcriptomic data derived from non-pathological human choroid and RPE cells.

FINDINGS

CSCR-associated genes such as PTPRB, CFH, and others are predominantly expressed in the choroidal endothelium as opposed to the RPE. The androgen receptor, encoded by the AR gene, demonstrates heightened expression in the macular endothelium compared to peripheral regions, unlike other steroid receptor genes. AR-expressing endothelial cells display an augmented responsiveness to Transforming growth factor beta (TGF-β), indicating a propensity towards endothelial to mesenchymal transition (endMT) transcriptional profiling.

INTERPRETATION

These results highlight the proclivity of CSCR to manifest primarily within the choroidal vasculature rather than the RPE, suggesting its categorization as a vascular eye disorder. This study accentuates the pivotal role of androgenic steroids, in addition to glucocorticoids. The observed linkage to TGF-β-mediated endMT provides a potential mechanistic insight into the disease's etiology.

Molecular pathogenesis, mechanism and therapy of Cav1 in prostate cancer

Prostate cancer is the second incidence of malignant tumors in men worldwide. Its incidence and mortality are increasing year by year. Enhanced expression of Cav1 in prostate cancer has been linked to both proliferation and metastasis of cancer cells, influencing disease progression. Dysregulation of the Cav1 gene shows a notable association with prostate cancer. Nevertheless, there is no systematic review to report about molecular signal mechanism of Cav1 and drug treatment in prostate cancer. This article reviews the structure, physiological and pathological functions of Cav1, the pathogenic signaling pathways involved in prostate cancer, and the current drug treatment of prostate cancer. Cav1 mainly affects the occurrence of prostate cancer through AKT/mTOR, H-RAS/PLCε, CD147/MMPs and other pathways, as well as substance metabolism including lipid metabolism and aerobic glycolysis. Baicalein, simvastatin, triptolide and other drugs can effectively inhibit the growth of prostate cancer. As a biomarker of prostate cancer, Cav1 may provide a potential therapeutic target for the treatment of prostate cancer.

Involvement of Testosterone Signaling in the Integrity of the Neurovascular Unit in the Male: Review of Evidence, Contradictions, and Hypothesis

Age-related central nervous system function decline and increased susceptibility of females compared to males with respect to prevalence of several neurodegenerative and neuropsychiatric diseases are both based on the principle that hormonal factors could be involved. These cerebral disorders are characterized by an alteration of blood-brain barrier (BBB) properties and chronic neuroinflammation, which lead to disease progression. Neuroinflammation, in turn, contributes to BBB dysfunction. The BBB and its environment, called the neurovascular unit (NVU), are crucial for cerebral homeostasis and neuronal function. Interestingly, sex steroids influence BBB properties and modulate neuroinflammatory responses. To date however, the majority of work reported has focused on the effects of estrogens on BBB function and neuroinflammation in female mammals. In contrast, the effects of testosterone signaling on the NVU in males are still poorly studied. The aim of this review was to summarize and discuss the literature, providing insights and contradictions to highlight hypothesis and the need for further investigations.

Changes in receptor location affect the ability of oxytocin to stimulate proliferative growth in prostate epithelial cells

In normal prostate cells, cell membrane receptors are located within signalling microdomains called caveolae. During cancer progression, caveolae are lost and sequestered receptors move out onto lipid rafts. The aim of this study was to investigate whether a change in the localisation of receptors out of caveolae and onto the cell membrane increased cell proliferation invitro, and to determine whether this is related to changes in the cell signalling pathways. Normal human prostate epithelial cells (PrEC) and androgen-independent (PC3) cancer cells were cultured with 10nM dihydrotestosterone (DHT). The effects of oxytocin (OT) and gonadal steroids on proliferation were assessed using the MTS assay. Androgen receptor (AR) and oxytocin receptor (OTR) expression was identified by immunofluorescence and quantified by western blot. OTR and lipid raft staining was determined using Pearson's correlation coefficient. Protein-protein interactions were detected and the cell signalling pathways identified. Treatment with OT did not affect the proliferation of PrEC. In PC3 cells, OT or androgen alone increased cell proliferation, but together had no effect. In normal cells, OTR localised to the membrane and AR localised to the nucleus, whereas in malignant cells both OTR and AR were identified in the cell membrane. Colocalisation of OTR and AR increased following treatment with androgens. Significantly fewer OTR/AR protein-protein interactions were seen in PrEC. With OT treatment, several cell signalling pathways were activated. Movement of OTR out of caveolae onto lipid rafts is accompanied by activation of alternative signal transduction pathways involved in stimulating increased cell proliferation.

Estrogen receptor signaling through metabotropic glutamate receptors

As the non-nuclear initiated effects of steroid hormone signaling have become more widely accepted, there has been a need to define the novel mechanisms of hormone receptor action that account for these outcomes. One mechanism that has emerged is the coupling of classical estrogen receptors (ERα and ERβ) with metabotropic glutamate receptors (mGluRs) to initiate G protein signaling cascades that ultimately influence neuronal physiology, structure, and behavior. Since its initial discovery in hippocampal neurons, evidence of ER/mGluR associations have been found throughout the nervous system, and the heterogeneity of possible receptor pairings afforded by multiple ER and mGluR subtypes appears to drive diverse molecular outcomes that can impact processes like cognition, motivation, movement, and pain. Recent evidence also suggests that the role of mGluRs in steroid hormone signaling may not be unique to ERs, but rather a conserved mechanism of membrane-initiated hormone receptor action.

Influence of Androgens on Immunity to Self and Foreign: Effects on Immunity and Cancer

It is well-known that sex hormones can directly and indirectly influence immune cell function. Different studies support a suppressive role of androgens on different components of the immune system by decreasing antibody production, T cell proliferation, NK cytotoxicity, and stimulating the production of anti-inflammatory cytokines. Androgen receptors have also been detected in many different cells of hematopoietic origin leading to direct effects of their ligands on the development and function of the immune system. The immunosuppressive properties of androgens could contribute to gender dimorphisms in autoimmune and infectious disease and thereby also hamper immune surveillance of tumors. Consistently, females generally are more prone to autoimmunity, while relatively less susceptible to infections, and have lower incidence and mortality of the majority of cancers compared to males. Some studies show that androgen deprivation therapy (ADT) can induce expansion of naïve T cells and increase T-cell responses. Emerging clinical data also reveal that ADT might enhance the efficacy of various immunotherapies including immune checkpoint blockade. In this review, we will discuss the potential role of androgens and their receptors in the immune responses in the context of different diseases. A particular focus will be on cancer, highlighting the effect of androgens on immune surveillance, tumor biology and on the efficacy of anti-cancer therapies including emerging immune therapies.

Recapitulation of prostate tissue cell type-specific transcriptomes by an in vivo primary prostate tissue xenograft model

Studies of the normal functions and diseases of the prostate request in vivo models that maintain the tissue architecture and the multiple-cell type compartments of human origin in order to recapitulate reliably the interactions of different cell types. Cell type-specific transcriptomes are critical to reveal the roles of each cell type in the functions and diseases of the prostate. A primary prostate tissue xenograft model was developed using fresh human prostate tissue specimens transplanted onto male mice that were castrated surgically and implanted with a device to maintain circulating testosterone levels comparable to adult human males. Endothelial cells and epithelial cells were isolated from 7 fresh human prostate tissue specimens and from primary tissue xenografts established from 9 fresh human prostate tissue specimens, using antibody-conjugated magnetic beads specific to human CD31 and human EpCAM, respectively. Transcriptomes of endothelial, epithelial and stromal cell fractions were obtained using RNA-Seq. Global and function-specific gene expression profiles were compared in inter-cell type and inter-tissue type manners. Gene expression profiles in the individual cell types isolated from xenografts were similar to those of cells isolated from fresh tissue, demonstrating the value of the primary tissue xenograft model for studies of the inter-relationships between prostatic cell types and the role of such inter-relationships in organ development, disease progression, and response to drug treatments.

mGluR5 Mediates Dihydrotestosterone-Induced Nucleus Accumbens Structural Plasticity, but Not Conditioned Reward

Gonadal hormones play a vital role in driving motivated behavior. They not only modulate responses to naturally rewarding stimuli, but also influence responses to drugs of abuse. A commonality between gonadal hormones and drugs of abuse is that they both impact the neurocircuitry of reward, including the regulation of structural plasticity in the nucleus accumbens (NAc). Previous hormonal studies have focused on the mechanisms and behavioral correlates of estradiol-induced dendritic spine changes in the female NAc. Here we sought to determine the effects of androgens on medium spiny neuron (MSN) spine plasticity in the male NAc. Following treatment with the androgen receptor agonist dihydrotestosterone (DHT), MSNs in castrated male rats exhibited a significant decrease in dendritic spine density. This effect was isolated to the shell subregion of the NAc. The effect of DHT was dependent on mGluR5 activity, and local mGluR5 activation and subsequent endocannabinoid signaling produce an analogous NAc shell spine decrease. Somewhat surprisingly, DHT-induced conditioned place preference remained intact following systemic inhibition of mGluR5. These findings indicate that androgens can utilize mGluR signaling, similar to estrogens, to mediate changes in NAc dendritic structure. In addition, there are notable differences in the direction of spine changes, and site specificity of estrogen and androgen action, suggesting sex differences in the hormonal regulation of motivated behaviors.

NRH:quinone oxidoreductase 2 (NQO2) and glutaminase (GLS) both play a role in large extracellular vesicles (LEV) formation in preclinical LNCaP-C4-2B prostate cancer model of progressive metastasis

In the course of studies aimed at the role of oxidative stress in the development of metastatic potential in the LNCaP-C4-2B prostate cancer progression model system, we found a relative decrease in the level of expression of the cytoplasmic nicotinamide riboside: quinone oxidoreductase (NQO2) and an increase in the oxidative stress in C4-2B cells compared to that in LNCaP or its derivatives C4 and C4-2. It was also found that C4-2B cells specifically shed large extracellular vesicles (LEVs) suggesting that these LEVs and their cargo could participate in the establishment of the osseous metastases. The level of expression of caveolin-1 increased as the system progresses from LNCaP to C4-2B. Since NQO2 RNA levels were not changed in LNCaP, C4, C4-2, and C4-2B, we tested an altered cellular distribution hypothesis of NQO2 being compartmentalized in the membrane fractions of C4-2B cells which are rich in lipid rafts and caveolae. This was confirmed when the detergent resistant membrane fractions were probed on immunoblots. Moreover, when the LEVs were analyzed for membrane associated caveolin-1 as possible cargo, we noticed that the enzyme NQO2 was also a component of the cargo along with caveolin-1 as seen in double immunofluorescence studies. Molecular modeling studies showed that a caveolin-1 accessible site is present in NQO2. Specific interaction between NQO2 and caveolin-1 was confirmed using deletion constructs of caveolin-1 fused with glutathione S-transferase (GST). Interestingly, whole cell lysate and mitochondrial preparations of LNCaP, C4, C4-2, and C4-2B showed an increasing expression of glutaminase (GLS, kidney type). The extrusion of LEVs appears to be a specific property of the bone metastatic C4-2B cells and this process could be inhibited by a GLS specific inhibitor BPTES, suggesting the critical role of a functioning glutamine metabolism. Our results indicate that a high level of expression of caveolin-1 in C4-2B cells contributes to an interaction between caveolin-1 and NQO2 and to their packaging as cargo in the shed LEVs. These results suggest an important role of membrane associated oxidoreductases in the establishment of osseous metastases in prostate cancer.

ARTIK-52 induces replication-dependent DNA damage and p53 activation exclusively in cells of prostate and breast cancer origin

The realization, that the androgen receptor (AR) is essential for prostate cancer (PC) even after relapse following androgen deprivation therapy motivated the search for novel types of AR inhibitors. We proposed that targeting AR expression versus its function would work in cells having either wild type or mutant AR as well as be independent of androgen synthesis pathways. Previously, using a phenotypic screen in androgen-independent PC cells we identified a small molecule inhibitor of AR, ARTIK-52. Treatment with ARTIK-52 caused the loss of AR protein and death of AR-positive, but not AR-negative, PC cells. Here we present data that ARTIK-52 induces degradation of AR mRNA through a mechanism that we were unable to establish. However, we found that ARTIK-52 is toxic to breast cancer (BC) cells expressing AR, although they were not sensitive to AR knockdown, suggesting an AR-independent mechanism of toxicity. Using different approaches we detected that ARTIK-52 induces replication-dependent double strand DNA breaks exclusively in cancer cells of prostate and breast origin, while not causing DNA damage, or any toxicity, in normal cells, as well as in non-PC and non-BC tumor cells, independent of their proliferation status. This amazing specificity, combined with such a basic mechanism of toxicity, makes ARTIK-52 a potentially useful tool to discover novel attractive targets for the treatment of BC and PC. Thus, phenotypic screening allowed us to identify a compound, whose properties cannot be predicted based on existing knowledge and moreover, uncover a barely known link between AR and DNA damage response in PC and BC epithelial cells.

Gene expression profiling analysis of castration-resistant prostate cancer

Background

Prostate cancer is a global health issue. Usually, men with metastatic disease will progress to castration-resistant prostate cancer (CRPC). We aimed to identify the differentially expressed genes (DEGs) in tumor samples from non-castrated and castrated men from LNCaP Orthotopic xenograft models of prostate cancer and to study the mechanisms of CRPC.

Material/Methods

In this work, GSE46218 containing 4 samples from non-castrated men and 4 samples from castrated men was downloaded from Gene Expression Omnibus. We identified DEGs using limma Geoquery in R, the Robust Multi-array Average (RMA) method in Bioconductor, and Bias methods, followed by constructing an integrated regulatory network involving DEGs, miRNAs, and TFs using Cytoscape. Then, we analyzed network motifs of the integrated gene regulatory network using FANMOD. We selected regulatory modules corresponding to network motifs from the integrated regulatory network by Perl script. We preformed gene ontology (GO) and pathway enrichment analysis of DEGs in the regulatory modules using DAVID.

Results

We identified total 443 DEGs. We built an integrated regulatory network, found three motifs (motif 1, motif 2 and motif 3), and got two function modules (module 1 corresponded to motif 1, and module 2 corresponded to motif 2). Several GO terms (such as regulation of cell proliferation, positive regulation of macromolecule metabolic process, phosphorylation, and phosphorus metabolic process) and two pathways (pathway in cancer and Melanoma) were enriched. Furthermore, some significant DEGs (such as CAV1, LYN, FGFR3 and FGFR3) were related to CPRC development.

Conclusions

These genes might play important roles in the development and progression of CRPC.

The evaluation of involvement of angiotensin II, its receptors, and androgen receptor in endometrial cancer

Endometrial cancer (EC) is the most common gynecological malignancy. Alterations of angiogenic factors including angiotensin (AngII) or VEGF are observed in EC. Expression of angiotensin receptor 1 (AT1) is correlated with EC. Moreover, the expression of VEGF is up-regulated by AngII. Androgens are involved in the pathogenesis of EC. Genetic variations in androgen receptor (AR) gene may increase EC risk. This review proved strong correlation among EC, AngII, its receptors and AR, where AT influence on AR and, as a result, induce the expression of genes related to carcinogenesis.

Differences in the transcriptional response to fulvestrant and estrogen deprivation in ER-positive breast cancer

PURPOSE

Endocrine therapies include aromatase inhibitors and the selective estrogen receptor (ER) downregulator fulvestrant. This study aimed to determine whether the reported efficacy of fulvestrant over anastrozole, and high- over low-dose fulvestrant, reflect distinct transcriptional responses.

EXPERIMENTAL DESIGN

Global gene expression profiles from ERα-positive breast carcinomas before and during presurgical treatment with fulvestrant (n = 22) or anastrozole (n = 81), and corresponding in vitro models, were compared. Transcripts responding differently to fulvestrant and estrogen deprivation were identified and integrated using Gene Ontology, pathway and network analyses to evaluate their potential significance.

RESULTS

The overall transcriptional response to fulvestrant and estrogen deprivation was correlated (r = 0.61 in presurgical studies, r = 0.87 in vitro), involving downregulation of estrogen-regulated and proliferation-associated genes. The transcriptional response to fulvestrant was of greater magnitude than estrogen deprivation (slope = 0.62 in presurgical studies, slope = 0.63 in vitro). Comparative analyses identified 28 genes and 40 Gene Ontology categories affected differentially by fulvestrant. Seventeen fulvestrant-specific genes, including CAV1/2, SNAI2, and NRP1, associated with ERα, androgen receptor (AR), and TP53, in a network regulating cell cycle, death, survival, and tumor morphology. Eighteen genes responding differently to fulvestrant specifically predicted antiproliferative response to fulvestrant, but not anastrozole. Transcriptional effects of low-dose fulvestrant correlated with high-dose treatment, but were of lower magnitude (ratio = 0.29).

CONCLUSIONS

The transcriptional response to fulvestrant has much in common with estrogen deprivation, but is stronger with distinctions potentially attributable to arrest of estrogen-independent ERα activity and involvement of AR signaling. Genes responding differently to fulvestrant may have predictive utility. These data are consistent with the clinical efficacy of fulvestrant versus anastrozole and higher dosing regimens.

PTRF/cavin-1 neutralizes non-caveolar caveolin-1 microdomains in prostate cancer

Caveolin-1 has a complex role in prostate cancer and has been suggested to be a potential biomarker and therapeutic target. As mature caveolin-1 resides in caveolae, invaginated lipid raft domains at the plasma membrane, caveolae have been suggested as a tumor-promoting signaling platform in prostate cancer. However, caveola formation requires both caveolin-1 and cavin-1 (also known as PTRF; polymerase I and transcript release factor). Here, we examined the expression of cavin-1 in prostate epithelia and stroma using tissue microarray including normal, non-malignant and malignant prostate tissues. We found that caveolin-1 was induced without the presence of cavin-1 in advanced prostate carcinoma, an expression pattern mirrored in the PC-3 cell line. In contrast, normal prostate epithelia expressed neither caveolin-1 nor cavin-1, while prostate stroma highly expressed both caveolin-1 and cavin-1. Utilizing PC-3 cells as a suitable model for caveolin-1-positive advanced prostate cancer, we found that cavin-1 expression in PC-3 cells inhibits anchorage-independent growth, and reduces in vivo tumor growth and metastasis in an orthotopic prostate cancer xenograft mouse model. The expression of α-smooth muscle actin in stroma along with interleukin-6 (IL-6) in cancer cells was also decreased in tumors of mice bearing PC-3-cavin-1 tumor cells. To determine whether cavin-1 acts by neutralizing caveolin-1, we expressed cavin-1 in caveolin-1-negative prostate cancer LNCaP and 22Rv1 cells. Caveolin-1 but not cavin-1 expression increased anchorage-independent growth in LNCaP and 22Rv1 cells. Cavin-1 co-expression reversed caveolin-1 effects in caveolin-1-positive LNCaP cells. Taken together, these results suggest that caveolin-1 in advanced prostate cancer is present outside of caveolae, because of the lack of cavin-1 expression. Cavin-1 expression attenuates the effects of non-caveolar caveolin-1 microdomains partly via reduced IL-6 microenvironmental function. With circulating caveolin-1 as a potential biomarker for advanced prostate cancer, identification of the molecular pathways affected by cavin-1 could provide novel therapeutic targets.

Expression profiles and functional associations of endogenous androgen receptor and caveolin-1 in prostate cancer cell lines

BACKGROUND

In prostate cancer (PCa) patients, the protein target for androgen deprivation and blockade therapies is androgen receptor (AR). AR interacts with many proteins that function to either co-activate or co-repress its activity. Caveolin-1 (Cav-1) is not found in normal prostatic epithelium, but is found in PCa, and may be an AR co-regulator protein.

METHODS

We investigated cell line-specific signatures and associations of endogenous AR and Cav-1 in six PCa cell lines of known androgen sensitivity: LNCaP (androgen sensitive); 22Rv1 (androgen responsive); PC3, DU145, and ALVA41 (androgen non-reliant); and RWPE1 (non-malignant). Protein and mRNA expression profiles were compared and electron microscopy used to identify cells with caveolar structures. For cell lines expressing both AR and Cav-1, knockdown techniques using small interfering RNA against AR or Cav-1 were used to test whether diminished expression of one affected the other. Co-sedimentation of AR and Cav-1 was used to test their association. A reporter assay for AR genomic activity was utilized following Cav-1 knockdown.

RESULTS

AR-expressing LNCaP and 22Rv1 cells had low endogenous Cav-1 mRNA and protein. Cell lines that expressed little or no AR (DU145, PC3, ALVA41, and RWPE1) expressed high endogenous levels of Cav-1. AR knockdown in LNCaP cells had little effect on Cav-1, but Cav-1 knockdown inhibited AR expression and genomic activity.

CONCLUSIONS

These data show endogenous AR and Cav-1 mRNA and protein expression is inversely related in PCa cells, with Cav-1 acting on the androgen/AR signaling axis possibly as an AR co-activator, demonstrated by diminished AR genomic activity following Cav-1 knockdown.

Effect of an angiotensin II type 1 receptor blocker on caveolin-1 expression in prostate cancer cells

INTRODUCTION

Caveolin-1, the major structural protein of caveolae, interacts directly with the AT1 receptor. The biological functions of caveolin-1 in cancer are compound, multifaceted, and depend on cell type, tumour grade and cancer stage. The AT1-R-caveolin complex in caveolae may coordinate angiotensin II (Ang II) induced signalling. The aim of this study was to determine the effect of the angiotensin II receptor type 1 blocker candesartan on caveolin expression in human metastatic prostate adenocarcinoma cells PC-3.

MATERIAL AND METHODS

WST-1 and BrdU assays were used as indicators of cell viability and proliferation after angiotensin II and/or candesartan stimulation. Real-time RT-PCR and western blot were used to study the effect of Ang II and/or candesartan on the expression of Cav-1 and AT1-R in PC-3 cells.

RESULTS

We found that the expression of caveolin-1 mRNA in the PC-3 cells treated with CV was significantly decreased in comparison with the control (2.9 ±0.17, 4.7 ±0.6, p < 0.05), whereas a higher caveolin-1 mRNA expression was observed in those after Ang II treatment (6.0 ±0.43, 4.7 ±0.6, p < 0.05). Protein analysis indicate that the expression of caveolin-1 protein in the PC-3 cells treated with candesartan was significantly decreased when compared with the control (0.69 ±0.05, 1.6 ±0.12, p < 0.05), whereas higher caveolin-1 protein expression was observed after Ang II treatment (2.5 ±0.20, 1.6 ±0.12, p < 0.05).

CONCLUSIONS

These results provide new information on the action of candesartan and may improve the knowledge about AT1 receptor inhibitors, which can be potentially useful in prostate cancer therapy.

Small-molecule hormones: molecular mechanisms of action

Small-molecule hormones play crucial roles in the development and in the maintenance of an adult mammalian organism. On the molecular level, they regulate a plethora of biological pathways. Part of their actions depends on their transcription-regulating properties, exerted by highly specific nuclear receptors which are hormone-dependent transcription factors. Nuclear hormone receptors interact with coactivators, corepressors, basal transcription factors, and other transcription factors in order to modulate the activity of target genes in a manner that is dependent on tissue, age and developmental and pathophysiological states. The biological effect of this mechanism becomes apparent not earlier than 30-60 minutes after hormonal stimulus. In addition, small-molecule hormones modify the function of the cell by a number of nongenomic mechanisms, involving interaction with proteins localized in the plasma membrane, in the cytoplasm, as well as with proteins localized in other cellular membranes and in nonnuclear cellular compartments. The identity of such proteins is still under investigation; however, it seems that extranuclear fractions of nuclear hormone receptors commonly serve this function. A direct interaction of small-molecule hormones with membrane phospholipids and with mRNA is also postulated. In these mechanisms, the reaction to hormonal stimulus appears within seconds or minutes.

The androgen receptor in health and disease

Androgens play pivotal roles in the regulation of male development and physiological processes, particularly in the male reproductive system. Most biological effects of androgens are mediated by the action of nuclear androgen receptor (AR). AR acts as a master regulator of downstream androgen-dependent signaling pathway networks. This ligand-dependent transcriptional factor modulates gene expression through the recruitment of various coregulator complexes, the induction of chromatin reorganization, and epigenetic histone modifications at target genomic loci. Dysregulation of androgen/AR signaling perturbs normal reproductive development and accounts for a wide range of pathological conditions such as androgen-insensitive syndrome, prostate cancer, and spinal bulbar muscular atrophy. In this review we summarize recent advances in understanding of the epigenetic mechanisms of AR action as well as newly recognized aspects of AR-mediated androgen signaling in both men and women. In addition, we offer a perspective on the use of animal genetic model systems aimed at eventually developing novel therapeutic AR ligands.

The selective inhibitory effect of a synthetic tanshinone derivative on prostate cancer cells

BACKGROUND

Androgen receptor (AR) is the main therapeutic target for the treatment of prostate cancer (PCa). Anti-androgens to reduce or prevent androgens binding to AR are widely used to suppress AR-mediated PCa growth; however, the androgen depletion therapy (ADT) is only effective for a short period of time. Here we tested PTS33, a new sodium derivative of cryptotanshinone, which can effectively inhibit the DHT-induced AR transactivation and PCa cell growth, and then explored the effects of PTS33 on inhibiting the expressions of AR target genes and proteins.

METHODS

PCa cells, LNCaP, CWR22Rv1, C4-2, PC-3, and DU145, were treated with PTS33 and luciferase assay was used to evaluate the ability of each to regulate AR transactivation. RT-PCR was used to evaluate the mRNA levels of AR target genes such as PSA, TMPRSS2, and TMEPA1. Western blot was used to determine AR, PSA, estrogen receptor alpha (ERα), glucocorticoid receptor (GR), and progesterone receptor (PR) protein expression. Cell growth and IC50 were determined by MTT assay after 48 hr treatment.

RESULTS

Our data showed that PTS33 selectively inhibits AR activities, but PTS33 does not repress the activities of other nuclear receptors, including ERα, GR, and PR. At a low concentration, 2 µM of PTS33 effectively suppresses the growth of AR-positive PCa cells, and has little effect on AR-negative PCa cells. Furthermore, our data indicated that PTS33 could modulate AR transactivation and suppress the AR target genes (PSA, TMPRSS2, and TMEPA1) expression in both androgen responsive PCa LNCaP cells and castration-resistant C4-2 cells. In addition, PTS33 can also inhibit estrogen/Δ5-androstenediol induced AR activities. The mechanistic studies indicate that PTS33 can inhibit AR function by suppression of AR protein expression, the AR N-C interaction, and AR-coregulator interaction.

CONCLUSIONS

PTS33 has shown a good efficacy to inhibit AR transactivation, block AR regulated gene expression, and reduce cell growth in AR positive PCa cells. The structure of PTS33 could be used as a base for development of novel AR signaling inhibitors to treat PCa.

Expression of PTRF in PC-3 Cells modulates cholesterol dynamics and the actin cytoskeleton impacting secretion pathways

Expression of caveolin-1 is up-regulated in prostate cancer metastasis and is associated with aggressive recurrence of the disease. Intriguingly, caveolin-1 is also secreted from prostate cancer cell lines and has been identified in secreted prostasomes. Caveolin-1 is the major structural component of the plasma membrane invaginations called caveolae. Co-expression of the coat protein Polymerase I and transcript release factor (PTRF) is required for caveolae formation. We recently found that expression of caveolin-1 in the aggressive prostate cancer cell line PC-3 is not accompanied by PTRF, leading to noncaveolar caveolin-1 lipid rafts. Moreover, ectopic expression of PTRF in PC-3 cells sequesters caveolin-1 into caveolae. Here we quantitatively analyzed the effect of PTRF expression on the PC-3 proteome using stable isotope labeling by amino acids in culture and subcellular proteomics. We show that PTRF reduced the secretion of a subset of proteins including secreted proteases, cytokines, and growth regulatory proteins, partly via a reduction in prostasome secretion. To determine the cellular mechanism accounting for the observed reduction in secreted proteins we analyzed total membrane and the detergent-resistant membrane fractions. Our data show that PTRF expression selectively impaired the recruitment of actin cytoskeletal proteins to the detergent-resistant membrane, which correlated with altered cholesterol distribution in PC-3 cells expressing PTRF. Consistent with this, modulating cellular cholesterol altered the actin cytoskeleton and protein secretion in PC-3 cells. Intriguingly, several proteins that function in ER to Golgi trafficking were reduced by PTRF expression. Taken together, these results suggest that the noncaveolar caveolin-1 found in prostate cancer cells generates a lipid raft microenvironment that accentuates secretion pathways, possibly at the step of ER sorting/exit. Importantly, these effects could be modulated by PTRF expression.

Understanding extranuclear (nongenomic) androgen signaling: what a frog oocyte can tell us about human biology

Steroids are key factors in a myriad of mammalian biological systems, including the brain, kidney, heart, bones, and gonads. While alternative potential steroid receptors have been described, the majority of biologically relevant steroid responses appear to be mediated by classical steroid receptors that are located in all parts of the cell, from the plasma membrane to the nucleus. Interestingly, these classical steroid receptors modulate different signals depending upon their location. For example, receptors in the plasma membrane interact with membrane signaling molecules, including G proteins and kinases. In contrast, receptors in the nucleus interact with nuclear signaling molecules, including transcriptional co-regulators. These extranuclear and intranuclear signals function together in an integrated fashion to regulate important biological functions. While most studies on extranuclear steroid signaling have focused on estrogens, recent work has demonstrated that nongenomic androgen signaling is equally important and that these two steroids modulate similar signaling pathways. In fact, by taking advantage of a simple model system whereby a physiologically relevant androgen-mediated process is regulated completely independent of transcription (Xenopus laevis oocyte maturation), many novel and conserved concepts in nongenomic steroid signaling have been uncovered and characterized.

Roles of cAMP and cAMP-dependent protein kinase in the progression of prostate cancer: cross-talk with the androgen receptor

Prostate carcinomas are among the most frequently diagnosed and death causing cancers affecting males in the developed world. It has become clear that the molecular mechanisms that drive the differentiation of normal prostate cells towards neoplasia involve multiple signal transduction cascades that often overlap and interact. A critical mediator of cellular proliferation and differentiation in various cells (and cancers) is the cAMP-dependent protein kinase, also known as protein kinase A (PKA), and its activating secondary messenger, cAMP. PKA and cAMP have been shown to play critical roles in prostate carcinogenesis and are the subject of this review. In particular we will focus on the cross-talk between PKA/cAMP signaling and that of the androgen receptor.