Publications (50)169.13 Total impact
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Article: Targeting heat shock proteins in prostate cancer.
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ABSTRACT: Heat shock proteins (HSPs) and chaperones are highly conserved stress-induced factors. They regulate not only protein folding and stability but are also actively involved in protein transport and transcriptional regulation. HSPs have cytoprotective roles and are essential for cancer cell survival. Noteworthy, HSPs are often upregulated in cancer. Therefore, HSPs emerged as drug targets for cancer therapy. Especially for prostate cancer (PCa) therapy, a battery of different compounds has been identified that act with different modes to inhibit PCa growth. The androgen receptor (AR) is a major player in PCa progression and is a well-known interacting factor of HSPs. Since the AR function is very dependent on HSP activity, many emerging compounds address the AR-associated HSPs as novel drug targets. Here, we provide an insight into the different classes of HSPs, their association with the human AR, the role of HSPs in human PCa development and review also the targeting of HSPs in human PCa. Further, the function and the underlying molecular mechanisms of specific compounds that are currently under investigation for the use against PCa growth will be comprehensively summarized.Current Medicinal Chemistry 03/2013; · 4.86 Impact Factor -
Article: The corepressor activity of Alien is controlled by CBP/p300.
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ABSTRACT: The regulation of gene repression by corepressors is a controlled process. Both SELDI-MS proteomic analysis and a yeast two-hybrid screen identified independently that the corepressor Alien interacts with the CBP coactivator. This interaction was further confirmed by co-immunoprecipitation and GST pull-down experiments suggesting that Alien interacts in vivo and in vitro with the histone acetyltransferases (HAT) coactivators CBP and its paralog p300. Acetylation detection experiments indicate that Alien is acetylated in vivo. Further, Alien interacts with the central region of CBP/p300 containing the HAT domain and becomes acetylated in vitro. Employing an inhibitor of the CBP/p300 HAT activity the Alien-mediated silencing was enhanced. Thus, these findings suggest a cross-talk between corepressors and coactivators and indicate a fine tuning of corepressor function by posttranslational modification through corepressor acetylation. © 2013 The Authors Journal compilation © 2013 FEBS.FEBS Journal 02/2013; · 3.79 Impact Factor -
Article: Computational and functional analysis of the androgen receptor antagonist atraric acid and its derivatives.
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ABSTRACT: Androgen receptor (AR) antagonists are important compounds for the treatment of prostate cancer (PCa). The atraric acid (AA), a natural compound, binds to the AR and acts as a specific AR antagonist. Interestingly, AA represents a novel chemical platform that could serve as a potential basis for new AR antagonists. Therefore, one objective of this study was to analyze the chemical/structural requirements for AR antagonism and to obtain predictions of where and how AA binds to the AR. Further, this study describes the chemical synthesis of 12 AA derivatives and their analysis using a combination of computational and functional assays. Functional analysis of AA derivatives indicated that none activated the AR. Both the para-hydroxyl group and the benzene ortho- and the meta-methyl groups of AA appeared to be essential to antagonize androgen-activated AR activity. Furthermore, extension of the hydrophobic side chain of AA led to slightly stronger AR antagonism. In silico data suggested that modifications to the basic AA structure change the hydrogen-bonding network with the AR ligand binding domain (LBD), so that the para-hydroxyl group of AA forms a hydrogen bond with the LBD, confirming the functional importance of this group for AR antagonism. Further, in silico modeling also suggested that the ortho- and meta- methyl groups of AA interact with hydrophobic residues of the ligand pocket of AR, which might explain their functional importance for antagonism. Thus, these studies identify the chemical groups within AA that play key roles in allowing the AA-based chemical platform to act as an AR antagonist.Anti-cancer agents in medicinal chemistry 11/2012; -
Article: Epigenetic involvement of Alien/ESET complex in thyroid hormone-mediated repression of E2F1 gene expression and cell proliferation.
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ABSTRACT: The ligand-bound thyroid hormone receptor (TR) is known to repress via a negative TRE (nTRE) the expression of E2F1, a key transcription factor that controls the G1/S phase transition. Alien has been identified as a novel interacting factor of E2F1 and acts as a corepressor of E2F1. The detailed molecular mechanism by which Alien inhibits E2F1 gene expression remains unclear. Here, we report that the histone H3 lysine 9 (H3K9) methyltransferase (HMT) ESET is an integral component of the corepressor Alien complex and the Alien/ESET complex is recruited to both sites, the E2F1 and the nTRE site of the E2F1 gene while the recruitment to the negative thyroid hormone response element (nTRE) is induced by the ligand-bound TRβ1 within the E2F1 gene promoter. We show that, overexpression of ESET promotes, whereas knockdown of ESET releases, the inhibition of TRβ1-regulated gene transcription upon T3 stimulation; and H3K9 methylation is required for TRβ1-repressed transcription. Furthermore, depletion of ESET impairs thyroid hormone-repressed proliferation as well as the G1/S transition of the cell cycle. Taken together, our data indicate that ESET is involved in TRβ1-mediated transcription repression and provide a molecular basis of thyroid hormone-induced repression of proliferation.Biochemical and Biophysical Research Communications 11/2011; 415(4):650-5. · 2.48 Impact Factor -
Article: Ligand-dependent corepressor acts as a novel androgen receptor corepressor, inhibits prostate cancer growth, and is functionally inactivated by the Src protein kinase.
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ABSTRACT: The activated androgen receptor (AR) promotes prostate cancer (PCa) growth. AR antagonists repress the AR by recruitment of corepressors. Not much is known about the inactivation of AR by corepressors in the presence of agonists (androgens). Here we show that the corepressor LCoR acts as an androgen-dependent corepressor that represses human PCa growth in vivo. In line with this, progressive decrease of ligand-dependent corepressor expression was observed in the PCa TRAMP mouse model with increasing age. LCoR interacts with AR and is recruited to chromatin in an androgen-induced manner. Unexpectedly, the LXXLL motif of LCoR is dispensable for interaction with the AR. Rather, the data indicate that LCoR interacts with the AR DNA binding domain on DNA. Interestingly, the interaction of LCoR with AR is inhibited by signaling pathways that are associated with androgen-independent PCa. Here we also show that the Src kinase inactivates the corepressive function of LCoR. Interfering with endogenous Src function by a dominant negative Src mutant, the growth inhibitory activity of LCoR is enhanced in vivo in a xenograft mouse model system. Thus, our studies indicate a role of LCoR as an AR corepressor and a tumor suppressor. Further, the decreased expression or inactivation of LCoR is as an important step toward PCa carcinogenesis in vivo.Journal of Biological Chemistry 08/2011; 286(43):37108-17. · 4.77 Impact Factor -
Article: LCoR acts as a novel androgen receptor corepressor, inhibits prostate cancer growth and is functionally inactivated by the Src kinase
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ABSTRACT: The activated androgen receptor (AR) promotes prostate cancer (PCa) growth. AR- antagonists repress the AR by recruitment of corepressors. Not much is known about the inactivation of AR by corepressors in the presence of agonists (androgens). Here we show that the corepressor LCoR acts as an androgen-dependent corepressor that represses human PCa growth in vivo. In line with this, progressive decrease of LCoR expression was observed in the PCa TRAMP mouse model with increasing age. LCoR interacts with AR and is recruited to chromatin in an androgen-induced manner. Unexpectedly, the LXXLL motif of LCoR is dispensable for interaction with the AR, rather the data indicate that LCoR interacts with the AR-DBD on DNA. Interestingly, the interaction of LCoR with AR is inhibited by signaling pathways that are associated with androgen-independent PCa. Here we also show that the Src kinase inactivates the corepressive function of LCoR. Interfering with endogenous Src function by a dominant negative Src mutant, the growth inhibitory activity of LCoR is enhanced in vivo in xenograft mouse model system. Thus, our studies indicate the role of LCoR as an AR corepressor and a tumor suppressor. Further, the decreased expression or inactivation of LCoR is as an important step towards PCa carcinogenesis in vivo.Journal of Biological Chemistry 08/2011; · 4.77 Impact Factor -
Article: Androgen receptor-mediated gene repression.
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ABSTRACT: Androgens have an essential role in inducing the genetic program for masculinization during development. Androgens mediate their effect through the androgen receptor (AR), a ligand-controlled transcription factor and regulator of rapid signaling. Inactivated AR results in complete feminization. Androgens are also essential in later life for reproduction, behavior, muscle development, breast, and prostate growth. In general, androgens inhibit breast and promote prostate growth. In the latter context the AR is a major drug target. On the one hand, many insights have been obtained how the AR mediates gene activation on a molecular level. Gene activation is mediated by a battery of factors including coactivators, chromatin remodeling complex proteins and transcription factors which either directly or indirectly interact with the AR at DNA binding sites. On the other hand, there are important AR target genes that are repressed by androgen-bound AR. However, the underlying molecular mechanisms are poorly understood although genes repressed by AR are key factors involved in cell proliferation and invasion. Here, we summarize molecular mechanisms of AR-mediated gene repression, thereby differentiating between direct and indirect DNA/chromatin recruitment and between genomic and non-genomic effects.Molecular and Cellular Endocrinology 07/2011; 352(1-2):46-56. · 4.19 Impact Factor -
Article: Sodium butyrate induces cellular senescence in neuroblastoma and prostate cancer cells
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ABSTRACT: Cellular senescence leads to an irreversible block of cellular division capacity both in cell culture and in vivo. The induction of an irreversible cell cycle arrest is very useful for treatment of cancer. Histone deacetylases (HDACs) are considered as therapeutic targets to treat cancer patients. HDAC inhibitors repress cancer growth and are used in various clinical trials. Here, we analyzed whether sodium butyrate (NaBu), an inhibitor of class I and II HDACs, induces cellular senescence in neuroblastoma and prostate cancer (PCa) including an androgen-dependent as well as an androgen-independent human PCa cell line. We found that the HDAC inhibitors NaBu and valproic acid (VPA) induce cellular senescence in tumor cells. Interestingly, also an inhibitor of SIRT1, a class HDAC III, induces cellular senescence. Both neuroblastoma and human prostate cancer cell lines express senescence markers, such as the Senescence Associated-β-galactosidase (SA-β-Gal) and Senescence Associated Heterochromatin Foci (SAHF). Furthermore, NaBu down-regulates the proto-oncogenes c-Myc, Cyclin D1 and E2F1 mRNA levels. The mRNA level of the cell cycle inhibitor p16 remains unchanged whereas that of the tumor suppressor p21 is strongly up-regulated. Interestingly, NaBu treatment robustly increases reactive oxygen species (ROS) levels. These results indicate an epigenetic regulation and an association of HDAC inhibition and ROS production with cellular senescence. The data underline that tumor cells can be driven towards cellular senescence by HDAC inhibitors, which may further arise as a potent possibility for tumor suppression.Hormone molecular biology and clinical investigation 07/2011; 7(1):265–272. -
Article: A designed cell-permeable aptamer-based corepressor peptide is highly specific for the androgen receptor and inhibits prostate cancer cell growth in a vector-free mode.
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ABSTRACT: The repression of the androgen receptor (AR) activity is a major objective to inhibit prostate cancer growth. One underlying mechanism for efficient hormone therapy is based on corepressors that inactivate the AR. In line with this, castration-resistant prostate cancer is associated with malfunction or reduced corepressor action. To overcome this, the overexpression of endogenous corepressors, however, affects many other transcription factors. Therefore, an AR-specific corepressor could be of advantage. Using a yeast peptide aptamer two-hybrid screen with the full-length human AR, we identified a short amino acid-stretch that binds specifically to the human AR in yeast and in mammalian cells and not to the closely related progesterone or glucocorticoid receptors. Furthermore, fused to a silencing domain, this aptamer-based corepressor (AB-CoR) exhibits corepressor activity by inhibiting both the AR-mediated transactivation and expression of the AR target gene PSA. Furthermore, stable expression of the AB-CoR inhibits growth of human LNCaP prostate cancer cells. Moreover, we generated a cell-permeable AB-CoR by fusing a protein transduction domain to establish a vector-free transport system. Treatment of LNCaP cells with the bacterially expressed and affinity-purified cell-permeable AB-CoR peptide resulted in a significant inhibition of both AR-mediated transactivation and prostate cancer cell proliferation. Thus, generation of a novel AR-specific aptamer-based corepressor may present a vector-free inhibition of AR-dependent prostate cancer growth as a novel approach.Endocrinology 06/2011; 152(6):2174-83. · 4.46 Impact Factor -
Article: BCR-ABL- and Ras-independent activation of Raf as a novel mechanism of Imatinib resistance in CML.
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ABSTRACT: Although the BCR-ABL tyrosine kinase inhibitor Imatinib has undoubtedly revolutionized the therapy of chronic myeloid leukaemia (CML), acquired drug resistance remains a common problem in CML therapy. Resistance often arises from second-line mutations in BCR-ABL or overexpression of the BCR-ABL protein but in ~20% of CML cases resistance mechanisms do not involve altered BCR-ABL function. Imatinib-resistant CML cell lines have been widely used for comparative proteome/genome-wide expression screens in order to decipher resistance mechanisms but a clearcut molecular mechanism or molecular player in BCR-ABL-independent resistance to Imatinib has not yet evolved from those studies. Here, we report the identification of a novel mechanism for Imatinib resistance in CML cells with unaltered BCR-ABL function. Pharmacological analysis evidenced a constitutive, Imatinib-insensitive activation of the Erk-MAPK pathway in resistant cells. A systematic analysis of pathway constituents illustrated that Ras-GTP accumulation remained fully sensitive to Imatinib but c-Raf activity from serum-fed cultures was largely resistant to the drug's action. Sequencing excluded mutations in either B-Raf or c-Raf as the origin of resistance, indicating that a functional alteration in the regulation of c-Raf activity was responsible for this effect. Collectively, these findings highlight a novel mechanism of acquired Imatinib resistance based on the BCR-ABL and Ras-independent constitutive activation of the Erk-MAPK pathway through activated c-Raf, which could prove helpful for a better functional classification of the causes of Imatinib resistance in CML.International Journal of Oncology 06/2011; 39(3):585-91. · 2.40 Impact Factor -
Article: Antiandrogenic activity of anthranilic acid ester derivatives as novel lead structures to inhibit prostate cancer cell proliferation.
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ABSTRACT: A plant extract from the fruits of saw palmetto, which is currently used to treat the androgen-dependent benign prostatic hyperplasia and PCa, served as source for new structure variants. We investigated the antiandrogenic potential of an ethanolic total extract and one of its main aromatic components anthranilic acid. An androgen receptor-antagonistic (antiandrogenic) effect of the extract was evident, and although anthranilic acid itself revealed no remarkable effect, its methyl ester, methyl anthranilate, exhibited antiandrogenic potential. Based on this chemical structure, we synthesized and investigated the antiandrogenic activity of four AnA ester derivatives, which were either novel or only little described in literature. These AnA esters inhibit the androgen-dependent transactivation of both the wild-type (wt) androgen receptor and the androgen receptor point mutant T877A, which often occurs in refractory PCa. Moreover, they inhibit the androgen receptor-induced expression of the endogenous prostate-specific antigen. Importantly, AnA esters repress the growth of human PCa cells. Deletion analyses of androgen receptor propose that the antiandrogenic effect of anthranilic acid esters is mediated by the ligand-binding domain, most likely through direct binding, without affecting androgen receptor protein levels. Taken together, the data suggest antiandrogenic potential of anthranilic acid ester derivatives, which can serve as lead structures for novel antiandrogens.Chemical Biology & Drug Design 03/2011; 77(6):450-9. · 2.28 Impact Factor -
Article: Analysis of ligand-specific co-repressor binding to the androgen receptor.
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ABSTRACT: The recruitment of co-repressors to the androgen receptor is an important mechanism for reducing androgen-mediated gene activation. Importantly, co-repressors play a major role in the treatment of hormone-dependent growing tissue, such as prostate cancer and breast cancer. In line with this, co-repressor dysfunction seems to be a major player for development of castration-resistant prostate cancer or therapy-resistant breast cancer. The molecular basis of hormone therapy by particular antihormones (antagonists) for the androgen receptor (AR) is mediated by enhanced recruitment and activity of co-repressors that cause repression of AR target genes that regulate proliferation and alteration of cancer cells. Therefore co-repressor recruitment is a crucial molecular mechanism of gene repression as well as inhibition of cancer growth. Here we describe different strategies to investigate co-repressor recruitment to the AR. First, we developed a modified mammalian two-hybrid system to investigate the recruitment of co-repressors to the AR within mammalian cells. This assay is very useful for the identification of the molecular mechanism of new AR antagonists and for molecular analysis of castration-resistant prostate cancer expressing the AR. Second, we describe a technique to analyze the interaction of AR isolated from human prostate cancer cells with a newly generated AR-specific co-repressor peptide, which is bacterially expressed and affinity purified by glutathione-S-transferase affinity precipitation assays in vitro. In summary, these methods can greatly facilitate the study of AR-co-repressor interactions.Methods in molecular biology (Clifton, N.J.) 01/2011; 776:199-223. -
Article: Detection of ligand-selective interactions of the human androgen receptor by SELDI-MS-TOF.
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ABSTRACT: The human androgen receptor (AR) is expressed in nearly all prostate cancers (PCa) and is known to participate in tumor progression through the expression of genes involved in the proliferation and differentiation of PCa. It is suggested that different types of ligands induce a distinct AR conformation that would lead to a specific set of interacting partners for the AR, such as coactivators (CoA) and corepressors (CoR), heat shock proteins (HSP), remodeling factors, kinases, phosphatases, and transcription factors resulting in various degrees of AR activity and stability. The natural ligand of the AR, dihydrotestosterone (DHT), induces a transcriptionally active conformation of the AR while the steroidal antiandrogen cyproterone acetate (CPA) and the nonsteroidal compounds hydroxyflutamide (OHF), bicalutamide (Cas), and atraric acid (AA) prevent acquisition of a transcriptionally active conformation. The AR has, in addition to transactivation, other functional properties. However, the current known interaction partners of AR cannot explain the multitude of AR-mediated functions. Thus, many of the ligand-specific AR-interacting proteins still remain unidentified. Here we provide an assay system to assess AR interactions in LNCaP PCa cells. LNCaP cells were treated with the AR-agonist R1881 or AR-antagonists Cas or AA to induce ligand-specific cofactor (CoF) binding to the AR in vivo. Here we describe a method for the identification of ligand-selective interaction partners of AR combining immunological methods with surface-enhanced laser desorption/ionization (SELDI)--time of flight (TOF)--mass spectrometry (MS). Exemplified here is the interaction of a novel AR-CoF, the cell-cycle regulating protein cell division cycle-associated protein 2 (CDCA2) with AR in the presence of antagonist which is verified by a protein-protein interaction assay in vivo. This scheme can provide further insights into the molecular mechanisms of AR ligand selectivity.Methods in molecular biology (Clifton, N.J.) 01/2011; 776:225-51. -
Article: The ING tumor suppressors in cellular senescence and chromatin.
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ABSTRACT: ABSTRACT: The Inhibitor of Growth (ING) proteins represent a type II tumor suppressor family comprising five conserved genes, ING1 to ING5. While ING1, ING2 and ING3 proteins are stable components of the mSIN3a-HDAC complexes, the association of ING1, ING4 and ING5 with HAT protein complexes was also reported. Among these the ING1 and ING2 have been analyzed more deeply. Similar to other tumor suppressor factors the ING proteins are also involved in many cellular pathways linked to cancer and cell proliferation such as cell cycle regulation, cellular senescence, DNA repair, apoptosis, inhibition of angiogenesis and modulation of chromatin.A common structural feature of ING factors is the conserved plant homeodomain (PHD), which can bind directly to the histone mark trimethylated lysine of histone H3 (H3K4me3). PHD mutants lose the ability to undergo cellular senescence linking chromatin mark recognition with cellular senescence. ING1 and ING2 are localized in the cell nucleus and associated with chromatin modifying enzymes, linking tumor suppression directly to chromatin regulation. In line with this, the expression of ING1 in tumors is aberrant or identified point mutations are mostly localized in the PHD finger and affect histone binding. Interestingly, ING1 protein levels increase in replicative senescent cells, latter representing an efficient pathway to inhibit cancer proliferation. In association with this, suppression of p33ING1 expression prolongs replicative life span and is also sufficient to bypass oncogene-induced senescence. Recent analyses of ING1- and ING2-deficient mice confirm a tumor suppressive role of ING1 and ING2 and also indicate an essential role of ING2 in meiosis.Here we summarize the activity of ING1 and ING2 as tumor suppressors, chromatin factors and in development.Cell & bioscience. 01/2011; 1(1):25. -
Article: 20-Aminosteroids as a novel class of selective and complete androgen receptor antagonists and inhibitors of prostate cancer cell growth.
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ABSTRACT: Here, the synthesis and the evaluation of novel 20-aminosteroids on androgen receptor (AR) activity is reported. Compounds 11 and 18 of the series inhibit both the wild type and the T877A mutant AR-mediated transactivation indicating AR antagonistic function. Interestingly, minor structural changes such as stereoisomers of the amino lactame moiety exhibit preferences for antagonism among wild type and mutant AR. Other tested nuclear receptors are only weakly or not affected. In line with this, the prostate cancer cell growth of androgen-dependent but not of cancer cells lacking expression of the AR is inhibited. Further, the expression of the prostate specific antigen used as a diagnostic marker is also repressed. Finally steroid 18 enhances cellular senescence that might explain in part the growth inhibition mediated by this derivative. Steroids 11 and 18 are the first steroids that act as complete AR antagonists and exhibit AR specificity.Bioorganic & medicinal chemistry 10/2010; 18(19):6960-9. · 2.82 Impact Factor -
Article: The natural compounds atraric acid and N-butylbenzene-sulfonamide as antagonists of the human androgen receptor and inhibitors of prostate cancer cell growth.
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ABSTRACT: Extracts from the plant Pygeum africanum are widely used in the therapy of benign prostate hyperplasia (BPH) and in combinational therapy for prostate cancer, the second leading cause of cancer death and the mostly diagnosed form of cancer in men. The androgen receptor (AR) plays a crucial role in the development of the prostate as well as in prostate diseases. Even though the extracts from P. africanum are considered as beneficial for prostate diseases in clinical trials, and some active compounds for treatment of BPH could be identified, compounds responsible for AR inhibition and the molecular mechanism for inhibition of prostatitis need to be identified. Recently, atraric acid and N-butylbenzene-sulfonamide were isolated from a selective dichlormethane extract of P. africanum as two novel AR antagonistic compounds. The molecular mechanisms of AR inhibition were analyzed and are summarized here. Both compounds are the first known natural, complete and specific AR antagonist.Molecular and Cellular Endocrinology 10/2010; 332(1-2):1-8. · 4.19 Impact Factor -
Article: NBBS isolated from Pygeum africanum bark exhibits androgen antagonistic activity, inhibits AR nuclear translocation and prostate cancer cell growth.
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ABSTRACT: Extracts from Pygeum africanum are used in the treatment of prostatitis, benign prostatic hyperplasia (BPH) and prostate cancer (PCa). The ligand-activated human androgen receptor (AR) is known to control the growth of the prostate gland. Inhibition of human AR is therefore a major goal in treatment of patients. Here, we characterize the compound N-butylbenzene-sulfonamide (NBBS) isolated from P. africanum as a specific AR antagonist. This antihormonal activity inhibits AR- and progesterone receptor- (PR) mediated transactivation, but not the related human glucocorticoid receptor (GR) or the estrogen receptors (ERα or ERβ). Importantly, NBBS inhibits both endogenous PSA expression and growth of human PCa cells. Mechanistically, NBBS binds to AR and inhibits its translocation to the cell nucleus. Furthermore, using a battery of chemically synthesized derivatives of NBBS we revealed important structural aspects for androgen antagonism and have identified more potent AR antagonistic compounds. Our data suggest that NBBS is one of the active compounds of P. africanum bark and may serve as a naturally occurring, novel therapeutic agent for treatment of prostatic diseases. Thus, NBBS and its derivatives may serve as novel chemical platform for treatment prostatitis, BPH and PCa.Investigational New Drugs 09/2009; 28(6):729-43. · 3.36 Impact Factor -
Article: Bag-1M inhibits the transactivation of the glucocorticoid receptor via recruitment of corepressors.
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ABSTRACT: The Bcl-2 associated athanogene 1M (Bag-1M) is known to repress the transactivation of the glucocorticoid receptor (GR). We report here that Bag-1M inhibits the action of GR via recruitment of corepressors, including nuclear receptor corepressor (NcoR) and silencing mediator for retinoic acid and thyroid hormone receptor (SMRT), and histone deacetylase (HDAC)3 to the genomic response element of a glucocorticoid-regulated human metallothionein IIa (hMTIIa) gene. A mutant GR lacking the interaction with BAG-1M fails to recruit the corepressors NcoR and SMRT. RNAi-mediated knock down of corepressors and the use of HDAC inhibitor relieved Bag-1M-induced repression on the transactivation of the GR. In addition, Bag-1M is not involved in the degradation of the receptor. These findings indicate a novel mechanism by which Bag-1M acts as a corepressor and downregulates the activity of the GR.FEBS letters 09/2009; 583(15):2451-6. · 3.54 Impact Factor -
Article: Regulation of the anaphase-promoting complex by the COP9 signalosome.
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ABSTRACT: The COP9 complex (signalosome) is a known regulator of the proteasome/ubiquitin pathway. Furthermore it regulates the activity of the cullin-RING ligase (CRL) families of ubiquitin E3-complexes. Besides the CRL family, the anaphase-promoting complex (APC/C) is a major regulator of the cell cycle. To investigate a possible connection between both complexes we assessed interacting partners of COP9 using an in vivo protein-protein interaction assay. Hereby, we were able to show for the first time that CSN2, a subunit of the COP9 signalosome, interacts physically with APC/C. Furthermore, we detected a functional influence of the COP9 complex regarding the stability of several targets of the APC/C. Consistent with these data we showed a genetic instability of cells overexpressing CSN2.Cell cycle (Georgetown, Tex.) 08/2009; 8(13):2041-9. · 5.36 Impact Factor -
Article: The natural compound atraric acid is an antagonist of the human androgen receptor inhibiting cellular invasiveness and prostate cancer cell growth.
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ABSTRACT: Extracts from Pygeum africanum are used in the treatment of prostatitis, benign prostatic hyperplasia and prostate cancer (Pca), major health problems of men in Western countries. The ligand-activated human androgen receptor (AR) supports the growth of the prostate gland. Inhibition of human AR by androgen ablation therapy and by applying synthetic anti-androgens is therefore the primary goal in treatment of patients. Here, we show that atraric acid (AA) isolated from bark material of Pygeum africanum has anti-androgenic activity, inhibiting the transactivation mediated by the ligand-activated human AR. This androgen antagonistic activity is receptor specific and does not inhibit the closely related glucocorticoid or progesterone receptors. Mechanistically, AA inhibits nuclear transport of AR. Importantly, AA is able to efficiently repress the growth of both the androgen-dependent LNCaP and also the androgen-independent C4-2 Pca cells but not that of PC3 or CV1 cells lacking AR. In line with this, AA inhibits the expression of the endogenous prostate specific antigen gene in both LNCaP und C4-2 cells. Analyses of cell invasion revealed that AA inhibits the invasiveness of LNCaP cells through extracellular matrix. Thus, this study provides a molecular insight for AA as a natural anti-androgenic compound and may serve as a basis for AA derivatives as a new chemical lead structure for novel therapeutic compounds as AR antagonists, that can be used for prophylaxis or treatment of prostatic diseases.Journal of Cellular and Molecular Medicine 08/2009; 13(8B):2210-23. · 4.13 Impact Factor
Top co-authors
Top Journals
Institutions
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2005–2013
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Friedrich-Schiller-Universität Jena
Jena, Thuringia, Germany
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2011
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Tianjin Medical University
Harbin, Heilongjiang Sheng, China -
University of Wisconsin, Madison
- Department of Dermatology
Madison, MS, USA
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2008
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Leuven University College
Leuven, VLG, Belgium
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2007
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Universitätsklinikum Jena
Jena, Thuringia, Germany
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2006
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Philipps-Universität Marburg
- Institut für Pharmazeutische Chemie
Marburg an der Lahn, Hesse, Germany
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2002–2005
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Justus-Liebig-Universität Gießen
- Institut für Genetik
Gießen, Hesse, Germany
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