Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It is widely suspected that androgen-independent prostate cancer growth depends on androgen receptor signaling via ill-defined mechanisms. Prostate-specific antigen (PSA) expression is often used to measure androgen receptor activity in cells and prostate cancer progression in patients. In the present study, we have compared androgen receptor activity using PSA and human male germ cell-associated kinase (hMAK), as read-outs in androgen-dependent LNCaP and androgen-independent C4-2B cells. As expected, very little PSA and hMAK expression were detected in LNCaP cells in the absence of androgens, whereas substantial expression of PSA was observed only in C4-2B cells under the same conditions. The addition of dihydrotestosterone to the culture medium increased the expression of both genes in both cell types. Comprehensive chromatin immunoprecipitation analysis of the entire PSA locus and an androgen-response element in hMAK unexpectedly revealed that androgen receptor was not occupying any site in the absence of dihydrotestosterone in either cell type. In line with the expression data, and in the absence of dihydrotestosterone, histone acetylation and RNA polymerase II occupancy was substantial at the PSA locus in C4-2B but not in LNCaP cells. In the presence of dihydrotestosterone, androgen receptor was found to occupy mainly the enhancer region of PSA in both cell types, accompanied with increases in histone acetylation and RNA polymerase II occupancy. Although the androgen receptor was not directly involved in the androgen-independent expression of PSA in C4-2B cells, small interfering RNA knock-down of androgen receptor significantly reduced PSA expression in both the presence and absence of dihydrotestosterone. In contrast, hMAK expression was decreased only in the presence of dihydrotestosterone after androgen receptor knock-down. We conclude that androgen-independent expression of PSA in C4-2B cells does not rely on the direct occupancy of the androgen receptor at the PSA locus, but is nevertheless affected indirectly via unknown androgen receptor-dependent mechanism(s) that influence the expression from some but not all androgen receptor target genes.
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PMID:Androgen receptor-dependent PSA expression in androgen-independent prostate cancer cells does not involve androgen receptor occupancy of the PSA locus. 1614 Sep 73

The current understanding of the response of androgen receptor to pharmacologic inhibitors in prostate cancer is derived primarily from serum prostate-specific antigen (PSA) levels. In this study, we test whether a novel androgen receptor-specific molecular imaging system is able to detect the action of the antiandrogen flutamide on androgen receptor function in xenograft models of prostate cancer. Adenoviruses bearing an optical imaging cassette containing an androgen receptor-responsive two-step transcriptional amplification system were injected into androgen-dependent and hormone-refractory tumors of animals undergoing systemic time-controlled release of the antiandrogen flutamide. Imaging of tumors with a cooled charge-coupled device camera revealed that the response of AdTSTA to flutamide is more sensitive and robust than serum PSA measurements. Flutamide inhibits the androgen signaling pathway in androgen-dependent but not refractory tumors. Analysis of androgen receptor and RNA polymerase II binding to the endogenous PSA gene by chromatin immunoprecipitation revealed that flutamide treatment and androgen withdrawal have different molecular mechanisms. The application of imaging technology to study animal models of cancer provides mechanistic insight into antiandrogen targeting of androgen receptor during disease progression.
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PMID:Imaging androgen receptor function during flutamide treatment in the LAPC9 xenograft model. 1627 87

In females, progesterone is associated with reproductive functions. In males, its role and the expression of its genomic receptor are not very well understood. In attempts to achieve a hormonal male contraceptive method, gestagens are used to downregulate gonadotropin and sperm production. It is therefore essential to understand the mechanism of action of progesterone at the molecular level in males, especially in primates. This investigation was undertaken: (a) to determine whether the genomic progesterone receptor is expressed in males; and (b) to locate it in various organs that are potential targets of gestagens. Human tissues were obtained at surgery for benign prostatic hyperplasia or prostate cancer and at autopsy. Non-human primate tissues were obtained at autopsy. This study was performed by analyzing the genomic progesterone receptor by immunohistochemistry, Western blot and RT-PCR. The nuclear progesterone receptor was expressed in pituitary and hypothalamus of both monkeys and men. In the testis progesterone receptor expression was found in a few peritubular and interstitial cells, but not in germ cells. In addition, expression was detected in the epididymis, prostate and male mammary gland. Reverse transcriptase (RT)-PCR experiments indicated that progesterone receptor A and B are expressed in all tissues analyzed. These data exclude direct genomic effects of gestagens at the spermatogenic level but indicate that a male contraceptive based on gestagens might have some effects on other tissues, such as the epididymis, prostate and mammary gland.
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PMID:Tissue expression of the nuclear progesterone receptor in male non-human primates and men. 1673 84

Androgen receptor (AR) is a ligand-induced transcriptional factor, which plays an important role in the normal development of prostate as well as in the progression of prostate cancer. Numerous coactivators, which associate with AR and function to remodel chromatin and recruit RNA polymerase II to enhance the transcriptional potential of AR, have been identified. Among these coactivators, few are protein kinases. In this study, we describe the characterization of a novel protein kinase, male germ cell-associated kinase (MAK), which serves as a coactivator of AR. We present evidence, which indicates that (a) MAK physically associates with AR (MAK and AR are found to be coprecipitated from cell extracts, colocalized in nucleus, and corecruited to prostate-specific antigen promoter in LNCaP as well as in transfected cells); (b) MAK is able to enhance AR transactivation potential in an androgen- and kinase-dependent manner in several prostate cancer cells and synergize with ACTR/steroid receptor coactivator-3 coactivator; (c) small hairpin RNA (shRNA) knocks down MAK expression resulting in the reduction of AR transactivation ability; (d) MAK-shRNA or kinase-dead mutant, when introduced into LNCaP cells, reduces the growth of the cells; and (e) microarray analysis of LNCaP cells carrying kinase-dead MAK mutant showed a significant impediment of AR signaling, indicating that endogenous MAK plays a general role in AR function in prostate cancer cells and likely to be a general coactivator of AR in prostate tissues. The highly restricted expression of this kinase makes it a potentially useful target for intervention of androgen independence.
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PMID:Male germ cell-associated kinase, a male-specific kinase regulated by androgen, is a coactivator of androgen receptor in prostate cancer cells. 1695 Nov 54

The androgen receptor (AR) plays a key role as a transcriptional factor in prostate development and carcinogenesis. Identification of androgen-regulated genes is essential to elucidate the AR pathophysiology in prostate cancer. Here, we identified androgen target genes that are directly regulated by AR in LNCaP cells, by combining chromatin immunoprecipitation (ChIP) with tiling microarrays (ChIP-chip). ChIP-enriched or control DNAs from the cells treated with R1881 were hybridized with the ENCODE array, in which a set of regions representing approximately 1% of the whole genome. We chose 10 bona fide AR-binding sites (ARBSs) (P<1e-5) and validated their significant AR recruitment ligand dependently. Eight upregulated genes by R1881 were identified in the vicinity of the ARBSs. Among the upregulated genes, we focused on UGT1A and CDH2 as AR target genes, because the ARBSs close to these genes (in UGT1A distal promoter and CDH2 intron 1) were most significantly associated with acetylated histone H3/H4, RNA polymerase II and p160 family co-activators. Luciferase reporter constructs including those two ARBSs exhibited ligand-dependent transcriptional regulator/enhancer activities. The present study would be powerful to extend our knowledge of the diversity of androgen genetic network and steroid action in prostate cancer cells.
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PMID:Identification of novel androgen response genes in prostate cancer cells by coupling chromatin immunoprecipitation and genomic microarray analysis. 1729 73

Apigenin, a dietary plant-flavonoid has shown anti-proliferative and anticancer properties, however the molecular basis of this effect remains to be elucidated. We studied the molecular events of apigenin action in human prostate cancer cells. Treatment of LNCaP and PC-3 cells with apigenin causes G0-G1 phase arrest, decrease in total Rb protein and its phosphorylation at Ser780 and Ser807/811 in dose- and time-dependent fashion. Apigenin treatment caused increased phosphorylation of ERK1/2 and JNK1/2 and this sustained activation resulted in decreased ELK-1 phosphorylation and c-FOS expression thereby inhibiting cell survival. Use of kinase inhibitors induced ERK1/2 phosphorylation, albeit at different levels, and did not contribute to cell cycle arrest in comparison to apigenin treatment. Despite activation of MAPK pathway, apigenin caused a significant decrease in cyclin D1 expression that occurred simultaneously with the loss of Rb phosphorylation and inhibition of cell cycle progression. The reduced expression of cyclin D1 protein correlated with decrease in expression and phosphorylation of p38 and PI3K-Akt, which are regulators of cyclin D1 protein. Interestingly, apigenin caused a marked reduction in cyclin D1, D2 and E and their regulatory partners CDK 2, 4 and 6, operative in G0-G1 phase of the cell cycle. This was accompanied by a loss of RNA polymerase II phosphorylation, suggesting the effectiveness of apigenin in inhibiting transcription of these proteins. This study provides an insight into the molecular mechanism of apigenin in modulating various tyrosine kinases and perturbs cell cycle progression, suggesting its future development and use as anticancer agent in humans.
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PMID:Apigenin-induced cell cycle arrest is mediated by modulation of MAPK, PI3K-Akt, and loss of cyclin D1 associated retinoblastoma dephosphorylation in human prostate cancer cells. 1745 54

Transcriptional control by androgens via androgen receptor (AR) is strongly involved in prostate cancer development, but the critical target genes have remained elusive. We have characterized E twenty-six-like transcription factor 4 (ELK4) (also known as serum response factor accessory protein 1) as a novel AR target in human prostate cancer cells. In-silico screening identified three putative AR response elements (AREs) within -10 kb from the transcription start site of ELK4. Both ARE1 at -167/-153 and ARE2 at -481/-467 bound AR in vitro and mediated androgen induction as isolated elements in transcription assays in non-prostate cells. However, merely the ARE2 that cooperates with a proximal forkhead box A1-binding site was critical for the AR-dependent activation of ELK4 promoter in prostate cancer cells. Preferential loading of holo-AR onto the ARE2 and concomitant recruitment of RNA polymerase II onto the ELK4 promoter was confirmed in prostate cancer cells by chromatin immunoprecipitation. Database searches indicated that the expression of ELK4 is markedly increased in prostate cancers relative to normal prostates. Moreover, prostate cancer tissue immunostainings showed that nuclear ELK4 levels are significantly increased in androgen-refractory prostate cancers compared to untreated tumours. Reduction of the amount of ELK4 in LNCaP cells by RNAi retarded cell growth. In conclusion, ELK4 is a direct AR target in prostate cancer cells. Androgens may thus contribute to the growth of prostate cancer via influencing ELK4 levels.
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PMID:Identification of ETS-like transcription factor 4 as a novel androgen receptor target in prostate cancer cells. 1846 65

Transcriptional activity of the androgen receptor (AR) is crucial for growth and survival of prostate cancer even upon development of resistance to androgen ablation and antiandrogen therapies. Therefore, novel therapies that can suppress AR transcriptional activity when conventional hormone therapies fail are needed. Here, we show that histone deacetylase (HDAC) inhibitors, including SAHA (vorinostat) and LBH589, which are currently being tested in clinic, could be such a therapy. HDAC inhibitors block the AR-mediated transcriptional activation of many genes, including the TMPRSS2 gene involved in fusion with ETS family members in a majority of prostate cancers. Genetic knockdown of either HDAC1 or HDAC3 can also suppress expression of AR-regulated genes, recapitulating the effect of HDAC inhibitor treatment. Whereas HDAC inhibitor treatment can lower androgen receptor protein levels in prostate cancer cells, we show that independent of AR protein levels, HDAC inhibitors block AR activity through inhibiting the assembly of coactivator/RNA polymerase II complex after AR binds to the enhancers of target genes. Failed complex assembly is associated with a phase shift in the cyclical wave of AR recruitment that typically occurs in response to ligand treatment. HDAC inhibitors retain the ability to block AR activity in castration-resistant prostate cancer models and, therefore, merit clinical investigation in this setting. The HDAC-regulated AR target genes defined here can serve as biomarkers to ensure sufficient levels of HDAC inhibition.
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PMID:Histone deacetylases are required for androgen receptor function in hormone-sensitive and castrate-resistant prostate cancer. 1917 86

EGFR or ERBB2 contributes to prostate cancer (PCa) progression by activating the androgen receptor (AR) in hormone-poor conditions. Here, we investigated the mechanisms by which androgens regulate EGFR and ERBB2 expression in PCa cells. In steroid-depleted medium (SDM), EGFR protein was less abundant in androgen-sensitive LNCaP than in androgen ablation-resistant 22Rv1 cells, whereas transcript levels were similar. Dihydrotestosterone (DHT) treatment increased both EGFR mRNA and protein levels and stimulated RNA polymerase II recruitment to the EGFR gene promoter, whereas it decreased ERBB2 transcript and protein levels in LNCaP cells. DHT altered neither EGFR or ERBB2 levels nor the abundance of prostate-specific antigen (PSA), TMEPA1, or TMPRSS2 mRNAs in 22Rv1 cells, which express the full-length and a shorter AR isoform deleted from the COOH-terminal domain (ARDeltaCTD). The contribution of both AR isoforms to the expression of these genes was assessed by small interfering RNAs targeting only the full-length or both AR isoforms. Silencing of both isoforms strongly reduced PSA, TMEPA1, and TMPRSS2 transcript levels. Inhibition of both AR isoforms did not affect EGFR and ERBB2 transcript levels but decreased EGFR and increased ERBB2 protein levels. Proliferation of 22Rv1 cells in SDM was inhibited in the absence of AR and ARDeltaCTD. A further decrease was obtained with PKI166, an EGFR/ERBB2 kinase inhibitor. Overall, we showed that ARDeltaCTD is responsible for constitutive EGFR expression and ERBB2 repression in 22Rv1 cells and that ARDeltaCTD and tyrosine kinase receptors are necessary for sustained 22Rv1 cell growth.
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PMID:Androgen receptor controls EGFR and ERBB2 gene expression at different levels in prostate cancer cell lines. 1931 61

Although the routine use of serum PSA testing has undoubtedly increased prostate cancer detection, one of its main drawbacks has been its lack of specificity, which results in a high negative biopsy rate. Consequently, a large population of men with chronically elevated serum PSA and one or more negative biopsies has emerged. More accurate tests are needed that can help identify which patients are at high risk of developing prostate cancer, and for whom repeat prostate biopsies are mandatory. To improve the specificity of prostate cancer diagnosis, prostate-cancer-specific markers, such as prostate cancer gene 3 (PCA3), are needed. The strong association between PCA3 mRNA overexpression and malignant transformation of prostate epithelium indicates its potential as a diagnostic biomarker. Quantification of PCA3 mRNA levels in urine was found to help predict the outcome of prostate biopsies. The intensive and time-consuming reverse-transcriptase polymerase chain reaction PCA3 urine test has been translated successfully into the fast and easy transcription-mediated amplification (TMA)-based PCA3 test. This test is the first RNA-based molecular diagnostic assay in body fluids for prostate cancer that is available to urologists. This Review describes the translation of the molecular marker PCA3 from the research laboratory to clinical practice.
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PMID:The use of PCA3 in the diagnosis of prostate cancer. 1942 73


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