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Guido Verhoeven - One of the best experts on this subject based on the ideXlab platform.
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Androgens stimulate fatty acid synthase in the human prostate cancer cell line LNCaP
Cancer Research, 1997Co-Authors: Johannes V. Swinnen, Murielle Esquenet, Karine Goossens, Walter Heyns, Guido VerhoevenAbstract:In addition to modulation of cell proliferation and stimulation of prostate-specific antigen secretion, one of the most striking effects of Androgens on the human prostate cancer cell line LNCaP is the accumulation of neutral lipids. These lipids are synthesized de novo, suggesting that LNCaP cells express all enzymes required for endogenous lipogenesis and that the expression and/or activity of some of these enzymes is affected by Androgens. One of the key enzymes involved in lipogenesis is fatty acid synthase (FAS), a potential prognostic enzyme and therapeutic target that is found to be frequently overexpressed in a variety of cancers including prostate cancer. Here, using Northern blot analysis, the gene encoding FAS is shown to be abundantly expressed in LNCaP cells and in two other prostate cancer cell lines tested (PC-3 and DU-145). In LNCaP cells, Androgen treatment (10(-8) M R1881) causes a 3-4-fold increase in FAS mRNA levels. Concomitantly with the increase in FAS gene expression, Androgens induce a 10-12-fold stimulation of FAS activity. Effects are dose- and time-dependent and follow courses similar to those of the Androgen induction of lipid accumulation. In support of the involvement of the Androgen receptor, steroid specificity of regulation of FAS activity is in agreement with the aberrant ligand specificity of the mutated Androgen receptor in LNCaP cells. Stimulation of FAS activity is inhibited by the antiAndrogen Casodex (bicalutamide) and is absent in the Androgen receptor-negative cell lines PC-3 and DU-145. Taken together, these data demonstrate that Androgens, mediated by the Androgen receptor, stimulate the expression and activity of FAS and suggest that stimulation of FAS activity represents at least part of the mechanism by which Androgens induce the accumulation of neutral lipids in LNCaP cells.
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Androgens markedly stimulate the accumulation of neutral lipids in the human prostatic adenocarcinoma cell line lncap
Endocrinology, 1996Co-Authors: Johannes V. Swinnen, Murielle Esquenet, Walter Heyns, P P Van Veldhoven, Guido VerhoevenAbstract:Microscopic evaluation of LNCaP cells stained with the lipophilic dye Oil red O revealed that Androgens induce a marked stimulation of lipid droplet accumulation. As determined by quantitative analysis of the Oil red O extracted from the stained cells, stimulatory effects of the synthetic Androgen R1881 became apparent at concentrations as low as 10(-11) M. Maximal induction (15-fold) was reached at 10(-8) M. Increases were observed 2 days after hormone addition and were maximal 1 day later. Accumulation of lipid droplets was also induced by mibolerone (another synthetic Androgen) and by the natural Androgens testosterone and dihydrotestosterone. In agreement with the aberrant ligand specificity of the mutated Androgen receptor in LNCaP cells, stimulation of lipid accumulation was also apparent after treatment with progesterone and estradiol. Cortisol and the synthetic glucocorticoid dexamethasone were ineffective. The Androgen antagonist Casodex (bicalutamide) abolished the stimulatory effect of R1881, f...
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Androgen regulation of the messenger rna encoding diazepam binding inhibitor acyl coa binding protein in the human prostatic adenocarcinoma cell line lncap
Molecular and Cellular Endocrinology, 1994Co-Authors: Johannes V. Swinnen, Murielle Esquenet, Walter Heyns, Wilfried Rombauts, Guido VerhoevenAbstract:Abstract To study the mechanisms by which Androgens intervene in the regulation of growth and differentiation of human prostatic epithelial cells, cDNA clones encoding putative prostate-secreted proteins were characterized and tested as potential markers for Androgen action. One of the isolated cDNAs expressed diazepam-binding inhibitor/acyl-CoA-binding protein (DBI/ACBP), suggesting that this polypeptide, that has been implicated in a large number of biochemical processes, is expressed and secreted by prostate cells. As demonstrated by Northern blot analysis, the mRNA encoding DBI/ACBP was expressed in prostate tissue and in the three human prostatic adenocarcinoma cell lines tested: LNCaP, PC-3 and DU-145. In Androgen-sensitive LNCaP cells, the synthetic Androgen R1881 stimulated the DBI/ACBP steady state mRNA levels with half maximal effects at a concentration of 0.2 nM. Increases were a maximal 12 h after addition of the synthetic hormone. DBI/ACBP mRNA levels could also be stimulated by the synthetic Androgen mibolerone and by the natural Androgens testosterone and dihydrotestosterone. In agreement with the altered steroid specificity of the Androgen receptor in LNCaP cells, estradiol and progesterone also exerted a stimulatory effect. Cortisol and the synthetic glucocorticoid dexamethasone were without effect. Androgen stimulation of DBI/ACBP mRNA levels was abolished in the presence of the protein synthesis inhibitor cycloheximide, implying a role for labile or Androgen-induced proteins in this Androgen stimulation. This is in contrast to the Androgen stimulation of the mRNA encoding prostate-specific antigen (PSA), suggesting that different mechanisms are involved in the Androgen regulation of these two genes. Although further experiments are required to confirm that DBI/ACBP is secreted by prostatic epithelial cells, these data demonstrate that the mRNA encoding DBI/ACBP is expressed in prostate cells and is affected by Androgens in Androgen-responsive LNCaP cells.
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Androgens and the testis.
Verhandelingen - Koninklijke Academie voor Geneeskunde van België, 1992Co-Authors: Guido VerhoevenAbstract:: The present survey focuses on some unique features of the testis as an Androgen target tissue. Within the testis Androgens act in a paracrine rather than in an endocrine fashion. All the available evidence suggests that the concentration of Androgens that surrounds testicular target cells is much higher than that observed in peripheral target tissues, but the exact concentration remains unknown. The concentration of Androgens required to maintain spermatogenesis considerably exceeds that observed in the peripheral circulation although it is probably lower than that which exists within the testis. The effects of Androgens on spermatogenesis are indirect and are mediated by somatic cells. Sertoli cells are the most likely mediators of the effects of Androgens on germ cell development. These cells contain Androgen receptors which are upregulated by FSH and by Androgens and they respond to Androgens in vitro. They are not the only Androgen-responsive cells in the testis, however, and some effects of Androgens on Sertoli cells (epithelial cells) are indirect and are actually mediated by paracrine factors produced by underlying peritubular cells (mesenchymal cells). Androgen-regulated mesenchymal-epithelial interactions may not be limited to the testis but may be a more general feature of Androgen action in several target tissues and our data suggest that the mediators involved may be very similar or identical. A final interesting aspect of Androgen action in the testis is that the compartment which responds to Androgens (the tubular compartment) may locally modulate the activity of the compartment which is responsible for Androgen production (the interstitial compartment). A complex network of paracrine mediators is responsible for these interactions.
Johannes V. Swinnen - One of the best experts on this subject based on the ideXlab platform.
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Androgens stimulate fatty acid synthase in the human prostate cancer cell line LNCaP
Cancer Research, 1997Co-Authors: Johannes V. Swinnen, Murielle Esquenet, Karine Goossens, Walter Heyns, Guido VerhoevenAbstract:In addition to modulation of cell proliferation and stimulation of prostate-specific antigen secretion, one of the most striking effects of Androgens on the human prostate cancer cell line LNCaP is the accumulation of neutral lipids. These lipids are synthesized de novo, suggesting that LNCaP cells express all enzymes required for endogenous lipogenesis and that the expression and/or activity of some of these enzymes is affected by Androgens. One of the key enzymes involved in lipogenesis is fatty acid synthase (FAS), a potential prognostic enzyme and therapeutic target that is found to be frequently overexpressed in a variety of cancers including prostate cancer. Here, using Northern blot analysis, the gene encoding FAS is shown to be abundantly expressed in LNCaP cells and in two other prostate cancer cell lines tested (PC-3 and DU-145). In LNCaP cells, Androgen treatment (10(-8) M R1881) causes a 3-4-fold increase in FAS mRNA levels. Concomitantly with the increase in FAS gene expression, Androgens induce a 10-12-fold stimulation of FAS activity. Effects are dose- and time-dependent and follow courses similar to those of the Androgen induction of lipid accumulation. In support of the involvement of the Androgen receptor, steroid specificity of regulation of FAS activity is in agreement with the aberrant ligand specificity of the mutated Androgen receptor in LNCaP cells. Stimulation of FAS activity is inhibited by the antiAndrogen Casodex (bicalutamide) and is absent in the Androgen receptor-negative cell lines PC-3 and DU-145. Taken together, these data demonstrate that Androgens, mediated by the Androgen receptor, stimulate the expression and activity of FAS and suggest that stimulation of FAS activity represents at least part of the mechanism by which Androgens induce the accumulation of neutral lipids in LNCaP cells.
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Androgens markedly stimulate the accumulation of neutral lipids in the human prostatic adenocarcinoma cell line lncap
Endocrinology, 1996Co-Authors: Johannes V. Swinnen, Murielle Esquenet, Walter Heyns, P P Van Veldhoven, Guido VerhoevenAbstract:Microscopic evaluation of LNCaP cells stained with the lipophilic dye Oil red O revealed that Androgens induce a marked stimulation of lipid droplet accumulation. As determined by quantitative analysis of the Oil red O extracted from the stained cells, stimulatory effects of the synthetic Androgen R1881 became apparent at concentrations as low as 10(-11) M. Maximal induction (15-fold) was reached at 10(-8) M. Increases were observed 2 days after hormone addition and were maximal 1 day later. Accumulation of lipid droplets was also induced by mibolerone (another synthetic Androgen) and by the natural Androgens testosterone and dihydrotestosterone. In agreement with the aberrant ligand specificity of the mutated Androgen receptor in LNCaP cells, stimulation of lipid accumulation was also apparent after treatment with progesterone and estradiol. Cortisol and the synthetic glucocorticoid dexamethasone were ineffective. The Androgen antagonist Casodex (bicalutamide) abolished the stimulatory effect of R1881, f...
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Androgen regulation of the messenger rna encoding diazepam binding inhibitor acyl coa binding protein in the human prostatic adenocarcinoma cell line lncap
Molecular and Cellular Endocrinology, 1994Co-Authors: Johannes V. Swinnen, Murielle Esquenet, Walter Heyns, Wilfried Rombauts, Guido VerhoevenAbstract:Abstract To study the mechanisms by which Androgens intervene in the regulation of growth and differentiation of human prostatic epithelial cells, cDNA clones encoding putative prostate-secreted proteins were characterized and tested as potential markers for Androgen action. One of the isolated cDNAs expressed diazepam-binding inhibitor/acyl-CoA-binding protein (DBI/ACBP), suggesting that this polypeptide, that has been implicated in a large number of biochemical processes, is expressed and secreted by prostate cells. As demonstrated by Northern blot analysis, the mRNA encoding DBI/ACBP was expressed in prostate tissue and in the three human prostatic adenocarcinoma cell lines tested: LNCaP, PC-3 and DU-145. In Androgen-sensitive LNCaP cells, the synthetic Androgen R1881 stimulated the DBI/ACBP steady state mRNA levels with half maximal effects at a concentration of 0.2 nM. Increases were a maximal 12 h after addition of the synthetic hormone. DBI/ACBP mRNA levels could also be stimulated by the synthetic Androgen mibolerone and by the natural Androgens testosterone and dihydrotestosterone. In agreement with the altered steroid specificity of the Androgen receptor in LNCaP cells, estradiol and progesterone also exerted a stimulatory effect. Cortisol and the synthetic glucocorticoid dexamethasone were without effect. Androgen stimulation of DBI/ACBP mRNA levels was abolished in the presence of the protein synthesis inhibitor cycloheximide, implying a role for labile or Androgen-induced proteins in this Androgen stimulation. This is in contrast to the Androgen stimulation of the mRNA encoding prostate-specific antigen (PSA), suggesting that different mechanisms are involved in the Androgen regulation of these two genes. Although further experiments are required to confirm that DBI/ACBP is secreted by prostatic epithelial cells, these data demonstrate that the mRNA encoding DBI/ACBP is expressed in prostate cells and is affected by Androgens in Androgen-responsive LNCaP cells.
E Mulder - One of the best experts on this subject based on the ideXlab platform.
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effect of culture conditions on Androgen sensitivity of the human prostatic cancer cell line lncap
The Prostate, 1993Co-Authors: Erna G Langeler, Connie J C Van Uffelen, Gert J Van Steenbrugge, Marinus A Blankenstein, E MulderAbstract:Several effects of Androgens on LNCaP-FGC prostate tumor cells showed a biphasic pattern. Stimulation of growth and inhibition of secretion of prostatic acid phosphatase (PAP) was observed at low Androgen concentrations (below 1 nM of the synthetic Androgen R1881), and inhibition of growth and stimulation of PAP secretion was observed at higher concentrations. In contrast, prostate specific antigen (PSA) secretion did not show this biphasic response pattern. Comparable effects were found for two sublines of the LNCaPFGC cells: an early (passage 20, Androgen-dependent) and relatively late (passage 70, Androgen-sensitive) passage of the cells. Culturing of both sublines in the presence of a high concentration of Androgens (10 nM R1881) resulted initially in a decrease in growth rate, but the cells started to proliferate within 3 weeks. These cells became less sensitive to Androgens, lost their biphasic response pattern, and showed reduced Androgen receptor levels. Three weeks after removal of the excess of Androgens, the passage 70 cells regained a biphasic growth response to Androgens. Culture in medium without steroids but with EGF resulted in a decrease of both Androgen sensitivity and Androgen receptor level. In conclusion, rapid changes of the Androgen sensitivity and receptor level of the LNCaP cells occurred under the influence of culture conditions. These changes were partly reversible and, therefore, were most likely due to adaptation of the cells.
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the Androgen receptor in lncap cells contains a mutation in the ligand binding domain which affects steroid binding characteristics and response to antiAndrogens
The Journal of Steroid Biochemistry and Molecular Biology, 1992Co-Authors: Jos Veldscholte, Cor A Berrevoets, Carrie Risstalpers, George G J M Kuiper, A O Brinkmann, Jan Trapman, Guido Jenster, E MulderAbstract:Abstract The human prostate tumor cell line LNCaP containd an abnormal Androgen receptor system with broad steroid binding specificity. Progestagens, estradiol and several antiAndrogens compete with Androgens for binding to the Androgen receptor in the cells to a higher extent than in other Androgen sensitive systems. Optimal growth of LNCaP cells is observed after addition of the synthetic Androgen R1881 (0.1 nM). In addition, estrogens, progestagens and several antiAndrogens do not inhibit Androgen responsive growth, but have striking growth stimulatory effects and increase EGF receptor level and acid phosphatase secretion. We have found that the Androgen receptor in the LNCaP cells contains a single point mutation changing the sense of codon 868 (Thr to Ala) in the ligand binding domain. Expression vectors containing the normal or mutated Androgen receptor sequence were transfected into COS or HeLa cells. Androgens, progestagens, estrogens and several antiAndrogens bind the mutated Androgen receptor proteon and activate the expression of an Androgen-regulated reporter gene (GRE-tk-CAT), indicating that the mutation directly affects both binding specificity and the induction of gene expression. Interestingly, the antiAndrogen casodex showed antiAndrogenic properties in growth studies of LNCaP cells and did not induced reporter gene activity in Hela cells transfected with the mutant receptor. The mutated Androgen receptor of LNCaP cells is therefore a useful tool in the elucidation of different levels of action of steroids and antisteroids.
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a mutation in the ligand binding domain of the Androgen receptor of human lncap cells affects steroid binding characteristics and response to anti Androgens
Biochemical and Biophysical Research Communications, 1990Co-Authors: Jos Veldscholte, Cor A Berrevoets, Carrie Risstalpers, George G J M Kuiper, A O Brinkmann, Jan Trapman, Guido Jenster, Eric Claassen, H C J Van Rooij, E MulderAbstract:LNCaP prostate tumor cells contain an abnormal Androgen receptor system. Progestagens, estradiol and anti-Androgens can compete with Androgens for binding to the Androgen receptor and can stimulate both cell growth and excretion of prostate specific acid phosphatase. We have discovered in the LNCaP Androgen receptor a single point mutation changing the sense of codon 868 (Thr to Ala) in the ligand binding domain. Expression vectors containing the normal or mutated Androgen receptor sequence were transfected into COS or Hela cells. Androgens, progestagens, estrogens and anti-Androgens bind the mutated Androgen receptor protein and activate the expression of an Androgen-regulated reporter gene construct (GRE-tk-CAT). The mutation therefore influences both binding and the induction of gene expression by different steroids and antisteroids
Donald J. Tindall - One of the best experts on this subject based on the ideXlab platform.
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Androgen Action in Prostate Cancer - Androgen action in prostate cancer.
Hormones and Cancer, 2010Co-Authors: Sujit Basu, Donald J. TindallAbstract:Prostate cancer represents a major health problem in men worldwide. Androgens are required for the growth and maintenance of the prostate. Androgens act by binding to the Androgen receptor (AR), a nuclear receptor transcription factor present in the prostate tissues. Most prostate tumors also retain their Androgen dependence; therefore, Androgen ablation is usually the preferred initial therapeutic approach for the treatment of advanced prostate cancer patients. This review summarizes the current information regarding the role of Androgens in prostate cancer.
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The role of Androgens and the Androgen receptor in prostate cancer.
Cancer Letters, 2002Co-Authors: Jose D. Debes, Donald J. TindallAbstract:Prostate cancer (PCa) is the leading diagnosed malignancy in men in western countries. The relationship between Androgens and the Androgen receptor (AR) has been studied extensively in PCa. Plasma levels of Androgens show variations between different populations, and in many cases this correlates with PCa susceptibility. Indeed, exposure of the fetus to higher Androgen concentrations appears to be a risk factor for PCa. The AR is present in the majority of PCa, and its activation by Androgens leads to different proliferative, apoptotic and angiogenic events. These events are in turn mediated by dysregulation of cyclin-dependent kinases, apoptotic factors and even mutations in the AR. Although Androgen ablation has been the mainstay non-surgical treatment for this disease, most tumors will eventually become refractory to treatment. Different cellular mechanisms appear to be involved in the Androgen-independent progression of PCa, including cytokine and growth factor-mediated activation of the AR as well as neuroendocrine differentiation. Thus, an understanding of the cellular mechanisms involved in Androgen action may lead to better therapeutic targets for PCa.
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Disruption of Androgen receptor function inhibits proliferation of Androgen-refractory prostate cancer cells.
Cancer Research, 2002Co-Authors: Ofelia L. Zegarra-moro, Lucy J. Schmidt, Haojie Huang, Donald J. TindallAbstract:Prostate cancer cells depend on Androgens and the Androgen receptor (AR) for survival. However, after Androgen ablation therapy, tumors relapse to an Androgen-refractory state. To determine whether the Androgen receptor is critical for proliferation of Androgen-refractory prostate cancer cells, we disrupted the activity of the Androgen receptor with an antibody and an AR mRNA hammerhead ribozyme in the following cell lines: LNCaP (Androgen-sensitive), LNCaP-Rf and LNCaP-C4 (Androgen-refractory), and DU-145 (Androgen-insensitive). Microinjection of either antibody or ribozyme inhibited proliferation of Androgen-refractory cells. These findings demonstrate that the AR is critical for proliferation of Androgen-refractory cells, even in the absence of Androgens.
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Androgen Receptor Signaling in Androgen-Refractory Prostate Cancer
Journal of the National Cancer Institute, 2001Co-Authors: Michael E. Grossmann, Haojie Huang, Donald J. TindallAbstract:Prostate cancer is the second most prevalent cancer in males in the United States. Standard therapy relies on removing, or blocking the actions of, Androgens. In most cases, this therapy results in a regression of the cancer because the prostate and most primary prostate tumors depend on Androgens for growth and the avoidance of apoptosis. However, a portion of the cancers eventually relapse, at which point they are termed “Androgen refractory” and can no longer be cured by conventional therapy of any type. The precise molecular events that lead from Androgen-sensitive prostate cancer to Androgen-refractory prostate cancer are, therefore, of great interest. This reviewseeks to identify specific molecular events that may be linked directly to the progression to Androgen-refractory cancer. Some of the mechanisms appear to involve the Androgen receptor (AR) directly and include mutations in, or amplification of, the AR gene in a manner that allows the AR to respond to low doses of Androgens, other steroids, or antiAndrogens. In a less direct manner, coactivators may increase the sensitivity of the AR to Androgens and even other nonAndrogenic substances through a number of mechanisms. Additional indirect mechanisms that do not result from mutation of the AR may involve activation of the AR by peptide growth factors or cytokines or may involve bypassing the AR entirely via other cellular pathways. Identification of the role of these mechanisms in the progression to Androgenrefractory prostate cancer is critical for developing therapies capable of curing this disease. [J Natl Cancer Inst 2001;93: 1687–97]
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CLATHRIN GENE EXPRESSION IS Androgen REGULATED IN THE PROSTATE
Endocrinology, 1998Co-Authors: James L. Prescott, Donald J. TindallAbstract:Androgens are required for the development and function of the prostate. In a normal human prostate, Androgens control the synthesis of proteins such as prostate-specific antigen and human glandular kallikrein. The prostate secretes these proteins as well as a number of other compounds to form the prostatic fluid. Using differential display PCR to detect novel Androgen-regulated genes, clathrin heavy chain expression was identified as potentially being up-regulated by Androgens in the prostate cancer cell line LNCaP. We report here that the clathrin heavy chain and light chain genes are regulated by Androgens. Clathrin heavy chain messenger RNA was up-regulated by Androgens in a concentration- and time-specific manner in the LNCaP cell line. Translation of clathrin heavy chain messenger RNA was stimulated by Androgens. Steady state levels of clathrin light chains a and b were up-regulated in the presence of Androgen in LNCaP cells. Clathrin gene expression was examined in normal rat prostates, and similar...
Colleen C Nelson - One of the best experts on this subject based on the ideXlab platform.
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Androgen levels increase by intratumoral de novo steroidogenesis during progression of castration resistant prostate cancer
Cancer Research, 2008Co-Authors: Jennifer A Locke, Emma S Guns, Amy A Lubik, Hans Adomat, Stephen C Hendy, Catherine A Wood, Susan Ettinger, Martin E Gleave, Colleen C NelsonAbstract:Although systemic Androgen deprivation prolongs life in advanced prostate cancer, remissions are temporary because patients almost uniformly progress to a state of a castration-resistant prostate cancer (CRPC) as indicated by recurring PSA. This complex process of progression does not seem to be stochastic as the timing and phenotype are highly predictable, including the observation that most Androgen-regulated genes are reactivated despite castrate levels of serum Androgens. Recent evidence indicates that intraprostatic levels of Androgens remain moderately high following systemic Androgen deprivation therapy, whereas the Androgen receptor (AR) remains functional, and silencing the AR expression following castration suppresses tumor growth and blocks the expression of genes known to be regulated by Androgens. From these observations, we hypothesized that CRPC progression is not independent of Androgen-driven activity and that Androgens may be synthesized de novo in CRPC tumors leading to AR activation. Using the LNCaP xenograft model, we showed that tumor Androgens increase during CRPC progression in correlation to PSA up-regulation. We show here that all enzymes necessary for Androgen synthesis are expressed in prostate cancer tumors and some seem to be up-regulated during CRPC progression. Using an ex vivo radiotracing assays coupled to high-performance liquid chromatography-radiometric/mass spectrometry detection, we show that tumor explants isolated from CRPC progression are capable of de novo conversion of [ 14 C]acetic acid to dihydrotestosterone and uptake of [ 3 H]progesterone allows detection of the production of six other steroids upstream of dihydrotestosterone. This evidence suggests that de novo Androgen synthesis may be a driving mechanism leading to CRPC progression following castration. [Cancer Res 2008;68(15):6407–15]
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Androgen levels increase by intratumoral de novo steroidogenesis during progression of castration resistant prostate cancer
Cancer Research, 2008Co-Authors: Jennifer A Locke, Emma S Guns, Amy A Lubik, Hans Adomat, Stephen C Hendy, Catherine A Wood, Susan Ettinger, Martin E Gleave, Colleen C NelsonAbstract:Although systemic Androgen deprivation prolongs life in advanced prostate cancer, remissions are temporary because patients almost uniformly progress to a state of a castration-resistant prostate cancer (CRPC) as indicated by recurring PSA. This complex process of progression does not seem to be stochastic as the timing and phenotype are highly predictable, including the observation that most Androgen-regulated genes are reactivated despite castrate levels of serum Androgens. Recent evidence indicates that intraprostatic levels of Androgens remain moderately high following systemic Androgen deprivation therapy, whereas the Androgen receptor (AR) remains functional, and silencing the AR expression following castration suppresses tumor growth and blocks the expression of genes known to be regulated by Androgens. From these observations, we hypothesized that CRPC progression is not independent of Androgen-driven activity and that Androgens may be synthesized de novo in CRPC tumors leading to AR activation. Using the LNCaP xenograft model, we showed that tumor Androgens increase during CRPC progression in correlation to PSA up-regulation. We show here that all enzymes necessary for Androgen synthesis are expressed in prostate cancer tumors and some seem to be up-regulated during CRPC progression. Using an ex vivo radiotracing assays coupled to high-performance liquid chromatography-radiometric/mass spectrometry detection, we show that tumor explants isolated from CRPC progression are capable of de novo conversion of [(14)C]acetic acid to dihydrotestosterone and uptake of [(3)H]progesterone allows detection of the production of six other steroids upstream of dihydrotestosterone. This evidence suggests that de novo Androgen synthesis may be a driving mechanism leading to CRPC progression following castration.
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differential regulation of clusterin and its isoforms by Androgens in prostate cells
Journal of Biological Chemistry, 2007Co-Authors: Dawn R Cochrane, Zhou Wang, Martin E Gleave, Motosugu Muramaki, Colleen C NelsonAbstract:Clusterin mRNA levels were shown to increase dramatically in rat ventral prostate following castration, and clusterin was therefore originally thought to be repressed by Androgens. It was later discovered that the increased clusterin levels are most likely due to castration-induced apoptosis of the prostatic epithelium rather than direct action of the Androgen receptor (AR). In the studies presented here, LNCaP cells in culture and rat prostate organ culture were treated with Androgens. Clusterin mRNA and protein are shown to increase with Androgen treatment in a time- and dose-dependent manner. This induction of clusterin requires AR and can be inhibited by casodex, an AR antagonist. We have found that the first intron of the clusterin gene contains putative Androgen response elements. The intronic region is shown to be bound by AR in chromatin immunoprecipitation assays and is transactivated by AR in reporter assays. Two isoforms of clusterin result from alternate transcriptional start sites. Both isoforms are cytoprotective; however, Isoform 1 has the capacity to produce a splice variant that is apoptotic. Real time PCR was used to determine the response of the two isoforms to Androgens. Intriguingly, these results illustrated that Isoform 2 was up-regulated, whereas Isoform 1 was down-regulated by Androgens. Isoform 2 was also increased as the LNCaP xenograft tumor progressed to Androgen-independence, whereas Isoform 1 was unaltered. This Androgen regulation of clusterin may underline the cytoprotective role of Androgens in normal prostate physiology as well as play an antiapoptotic role in prostate cancer progression.
