Search

Androgen receptor (AR) signaling remains the key therapeutic target in the management of hormone-naïve-advanced prostate cancer (PCa) and castration-resistant PCa (CRPC). Recently, landmark molecular features have been reported for CRPC, including the expression of constitutively active AR variants that lack the ligand-binding domain. Besides their role in CRPC, AR variants lead to the expression of genes involved in tumor progression. However, little is known about the specificity of their mode of action compared with that of wild-type AR (AR-WT). We performed AR transcriptome analyses in an androgen-dependent PCa cell line as well as cross-analyses with publicly available RNA-seq datasets and established that transcriptional repression capacity that was marked for AR-WT was pathologically lost by AR variants. Functional enrichment analyses allowed us to associate AR-WT repressive function to a panel of genes involved in cell adhesion and epithelial-to-mesenchymal transition. So, we postulate that a less documented AR-WT normal function in prostate epithelial cells could be the repression of a panel of genes linked to cell plasticity and that this repressive function could be pathologically abrogated by AR variants in PCa., (© 2021 The Authors. Molecular Oncology published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)

The General Data Protection Regulation (GDPR) became binding law in the European Union Member States in 2018, as a step toward harmonizing personal data protection legislation in the European Union. The Regulation governs almost all types of personal data processing, hence, also, those pertaining to biomedical research. The purpose of this article is to highlight the main practical issues related to data and biological sample sharing that biomedical researchers face regularly, and to specify how these are addressed in the context of GDPR, after consulting with ethics/legal experts. We identify areas in which clarifications of the GDPR are needed, particularly those related to consent requirements by study participants. Amendments should target the following: (1) restricting exceptions based on national laws and increasing harmonization, (2) confirming the concept of broad consent, and (3) defining a roadmap for secondary use of data. These changes will be achieved by acknowledged learned societies in the field taking the lead in preparing a document giving guidance for the optimal interpretation of the GDPR, which will be finalized following a period of commenting by a broad multistakeholder audience. In parallel, promoting engagement and education of the public in the relevant issues (such as different consent types or residual risk for re-identification), on both local/national and international levels, is considered critical for advancement. We hope that this article will open this broad discussion involving all major stakeholders, toward optimizing the GDPR and allowing a harmonized transnational research approach.

Founded in 1919, the Society of Biology of Strasbourg (SBS) is a learned society whose purpose is the dissemination and promotion of scientific knowledge in biology. Subsidiary of the Society of Biology, the SBS celebrated its Centenary on Wednesday, the 16th of October 2019 on the Strasbourg University campus and at the Strasbourg City Hall. This day allowed retracing the various milestones of the SBS, through its main strengths, its difficulties and its permanent goal to meet scientific and societal challenges. The common thread of this day was the transmission of knowledge related to the past, the present, but also the future. At the start of the 21st century, the SBS must continue to reinvent itself to pursue its objective of transmitting scientific knowledge in biology and beyond. Scientific talks performed by senior scientists and former SBS thesis prizes awardees, a round table, and informal discussions reflected the history and the dynamism of the SBS association. All SBS Centennial participants have set the first milestone for the SBS Bicentennial., (© Société de Biologie, 2020.)

ZMIZ1 is a coactivator of several transcription factors, including p53, the androgen receptor, and NOTCH1. Here, we report 19 subjects with intellectual disability and developmental delay carrying variants in ZMIZ1. The associated features include growth failure, feeding difficulties, microcephaly, facial dysmorphism, and various other congenital malformations. Of these 19, 14 unrelated subjects carried de novo heterozygous single-nucleotide variants (SNVs) or single-base insertions/deletions, 3 siblings harbored a heterozygous single-base insertion, and 2 subjects had a balanced translocation disrupting ZMIZ1 or involving a regulatory region of ZMIZ1. In total, we identified 13 point mutations that affect key protein regions, including a SUMO acceptor site, a central disordered alanine-rich motif, a proline-rich domain, and a transactivation domain. All identified variants were absent from all available exome and genome databases. In vitro, ZMIZ1 showed impaired coactivation of the androgen receptor. In vivo, overexpression of ZMIZ1 mutant alleles in developing mouse brains using in utero electroporation resulted in abnormal pyramidal neuron morphology, polarization, and positioning, underscoring the importance of ZMIZ1 in neural development and supporting mutations in ZMIZ1 as the cause of a rare neurodevelopmental syndrome., (Copyright © 2018 American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.)

Prostate cancer is a public health concern as it currently represents the most frequent malignancy in men in Europe. Progression of this hormone-dependent cancer is driven by androgens. Thus, the most common treatment for patients with advanced prostate cancer consists in an androgen ablation by castration therapy. However, the majority of patients relapses and develops a castration-resistant prostate cancer. This failure of androgen deprivation is related to the emergence of mutant and splice variants of the androgen receptor. Indeed, androgen receptor variants are ligand-independent, constitutively active and thus able to induce resistance to castration. This review focuses on AR variants signaling pathways and their role in resistance to castration and prostate cancer progression., (© 2017 médecine/sciences – Inserm.)

Constitutively active androgen receptor (AR) variants have been involved in the expression of mesenchymal markers such as N-cadherin in prostate cancer (PCa). However, the underlying molecular mechanisms remain elusive. It remains unclear, whether N-cadherin gene (CDH2) is a direct transcriptional target of AR variants or whether the observed upregulation is due to indirect effects through additional regulatory factors. Moreover, the specific contribution of full-length AR and AR variants in N-cadherin regulation in PCa has never been explored deeply. To investigate this, we artificially mimicked the co-expression of AR variants together with a full-length AR and performed miRNA-seq, RNA-seq and ChIP assays. Our results were in favor of a direct AR variants action on CDH2. Our data also revealed a distinctive mode of action between full-length AR and AR variants to regulate N-cadherin expression. Both wild type AR and AR variants could interact with a regulatory element in intron 1 of CDH2. However, a higher histone H4 acetylation in this genomic region was only observed with AR variants. This suggests that full-length AR may play an occluding function to impede CDH2 upregulation. Our data further highlighted a negative effect of AR variants on the expression of the endogenous full-length AR in LNCaP. These differences in the mode of action of AR variants and full-length AR for the control of one key gene for prostate cancer progression could be worth considering for targeting AR variants in PCa., Competing Interests: CONFLICTS OF INTEREST The authors report no conflicts of interest.

Despite the advent of several new treatment options over the past years, advanced/metastatic prostate carcinoma (PCa) still remains incurable, which justifies the search for novel targets and therapeutic molecules. Nucleophosmin (NPM1) is a shuttling nucleoprotein involved in tumor growth and its targeting could be a potential approach for cancer therapy. We previously demonstrated that the multivalent pseudopeptide N6L binds to NPM1 potently affecting in vitro and in vivo tumor cell growth of various tumor types as well as angiogenesis. Furthermore, NPM1 binds to androgen receptor (AR) and modulate its activity. In this study, we first investigated the implication of the NPM1 and its Thr199 and Thr234/237 phosphorylated forms in PCa. We showed that phosphorylated forms of NPM1 interact with androgen receptor (AR) in nucleoplasm. N6L treatment of prostate tumor cells led to inhibition of NPM1 phosphorylation in conjunction with inhibition of AR activity. We also found that total and phosphorylated NPM1 were overexpressed in castration-resistant PCa. Assessment of the potential therapeutic role of N6L in PCa indicated that N6L inhibited tumor growth both in vitro and in vivo when used either alone or in combination with the standard-of-care first- (hormonotherapy) and second-line (docetaxel) treatments for advanced PCa. Our findings reveal the role of Thr199 and Thr234/237 phosphorylated NPM1 in PCa progression and define N6L as a new drug candidate for PCa therapy.

The skeleton is the preferred site for prostate cancer (PC) metastasis leading to incurable castration-resistant disease. The increased expression of genes encoding steroidogenic enzymes found in bone metastatic tissue from patients suggests that up-regulated steroidogenesis might contribute to tumor growth at the metastatic site. Because of the overall sclerotic phenotype, we hypothesize that osteoblasts regulate the intratumoral steroidogenesis of castration resistant prostate cancer (CRPC) in bone. We here show that osteoblasts alter the steroidogenic transcription program in CRPC cells, closely mimicking the gene expression pattern described in CRPC. Osteoblast-stimulated LNCaP-19 cells displayed an increased expression of genes encoding for steroidogenic enzymes (CYP11A1, HSD3B1, and AKR1C3), estrogen signaling-related genes (CYP19A1, and ESR2), and genes for DHT-inactivating enzymes (UGT2B7, UGT2B15, and UGT2B17). The observed osteoblast-induced effect was exclusive to osteogenic CRPC cells (LNCaP-19) in contrast to osteolytic PC-3 and androgen-dependent LNCaP cells. The altered steroid enzymatic pattern was specific for the intratibial tumors and verified by immunohistochemistry in tissue specimens from LNCaP-19 xenograft tumors. Additionally, the overall steroidogenic effect was reflected by corresponding levels of progesterone and testosterone in serum from castrated mice with intratibial xenografts. A bi-directional interplay was demonstrated since both proliferation and Esr2 expression of osteoblasts were induced by CRPC cells in steroid-depleted conditions. Together, our results demonstrate that osteoblasts are important mediators of the intratumoral steroidogenesis of CRPC and for castration-resistant growth in bone. Targeting osteoblasts may therefore be important in the development of new therapeutic approaches., (Copyright © 2015 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.)

Most of the biological effects of androgen hormones are mediated through an intracellular transcription factor, the androgen receptor (AR). This protein presents a long disordered N-terminal domain (NTD), known to aggregates into amyloid fibers.1 This aggregation property is usually associated with the presence of a poly-glutamine tract (polyQ), known to be involved in several pathologies.2 The NTD has gain interest recently because potential anti-prostate-cancer molecules could target this domain.3 Here, we characterize a conserved region of the NTD (distal from polyQ); it promotes the formation of amyloid fibers under mild oxidative conditions. Unlike most fibrils, which are irreversibly aggregated, the free peptides can be restored from the fibril by the addition of a reducing agent., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Androgen receptor (AR) signaling pathway remains the foremost target of novel therapeutics for castration-resistant prostate cancer (CRPC). However, the expression of constitutively active AR variants lacking the carboxy-terminal region in CRPC may lead to therapy inefficacy. These AR variants are supposed to support PCa cell growth in an androgen-depleted environment, but their mode of action still remains unresolved. Moreover, recent studies indicate that constitutively active AR variants are expressed in primary prostate tumors and may contribute to tumor progression. The aim of this study was to investigate the impact of constitutively active AR variants on the expression of tumor progression markers. N-cadherin expression was analyzed in LNCaP cells overexpressing the wild type AR or a constitutively active AR variant by qRT-PCR, Western blot and immunofluorescence. We showed here for the first time that N-cadherin expression was increased in the presence of constitutively active AR variants. These results were confirmed in C4-2B cells overexpressing these AR variants. Although N-cadherin expression is often associated with a downregulation of E-cadherin, this phenomenon was not observed in our model. Nevertheless, in addition to the increased expression of N-cadherin, an upregulation of other mesenchymal markers expression such as VIMENTIN, SNAIL and ZEB1 was observed in the presence of constitutively active variants. In conclusion, our findings highlight novel consequences of constitutively active AR variants on the regulation of mesenchymal markers in prostate cancer.

We have investigated the expression of prostate-specific membrane antigen (PSMA) and prostate-specific antigen (PSA) transcripts in androgen-dependent (LNCaP) and androgen-independent (22Rv1) prostate cancer cell lines. We also enquired whether Q640X CTE-truncated androgen receptor (AR) has an impact on transcription of mRNA for PSMA and PSA in transfected androgen-sensitive prostate cancer LNCaP cells. Wild type LNCaP, 22Rv1 prostate cancer cells, prostate stromal cells (PrSC) and LNCaP cells transfected with p-Q640X AR, p-WT AR or p-C3 empty plasmids were studied. The expression of PSMA and PSA were detected by real-time PCR after transfection for 4 and 7 days. Expression of mRNAs for PSA was sixfold greater than PSMA in wild type LNCaP cells. In contrast, the wild type androgen refractory 22Rv1 cell line reacted almost exactly the opposite way reverse to LNCaP cells, since the transcription of mRNA for PSMA almost twofold greater than PSA. Non-transfected human PrSC responded similarly to PSMA mRNA and PSA mRNA was not detected in these cells. Q640X AR transfected LNCaP cells downregulated the expression of PSMA and PSA genes after 7 days. Our results demonstrate that Q640X mutated AR may have an important regulatory role in mediating the PSMA and PSA genes expression during the progression of prostate cancer from androgen-dependence to androgen-independence. Understanding their functional properties and mechanisms by which ARs involved in regulation of PSMA and PSA expression will allow the identification of new target therapies for the treatment of hormone-resistant prostate cancer., (© 2013 International Federation for Cell Biology.)

Almost all prostate cancers respond to androgen deprivation treatment but many recur. We postulated that risk of hormone escape--frequency and delay--are influenced by hormone therapy modalities. More, hormone therapies induce crucial biological changes involving androgen receptors; some might be targets for escape prevention. We investigated the relationship between the androgen deprivation treatment and the risk of recurrence using nude mice bearing the high grade, hormone-dependent human prostate cancer xenograft PAC120. Tumor-bearing mice were treated by Luteinizing-Hormone Releasing Hormone (LHRH) antagonist alone, continuous or intermittent regimen, or combined with androgen receptor (AR) antagonists (bicalutamide or flutamide). Tumor growth was monitored. Biological changes were studied as for genomic alterations, AR mutations and protein expression in a large series of recurrent tumors according to hormone therapy modalities. Therapies targeting Her-2 or AKT were tested in combination with castration. All statistical tests were two-sided. Tumor growth was inhibited by continuous administration of the LH-RH antagonist degarelix (castration), but 40% of tumors recurred. Intermittent castration or complete blockade induced by degarelix and antiandrogens combination, inhibited tumor growth but increased the risk of recurrence (RR) as compared to continuous castration (RR(intermittent): 14.5, RR(complete blockade): 6.5 and 1.35). All recurrent tumors displayed new quantitative genetic alterations and AR mutations, whatever the treatment modalities. AR amplification was found after complete blockade. Increased expression of Her-2/neu with frequent ERK/AKT activation was detected in all variants. Combination of castration with a Her-2/neu inhibitor decreased recurrence risk (0.17) and combination with an mTOR inhibitor prevented it. Anti-hormone treatments influence risk of recurrence although tumor growth inhibition was initially similar. Recurrent tumors displayed genetic instability, AR mutations, and alterations of phosphorylation pathways. We postulated that Her-2/AKT pathways allowed salvage of tumor cells under castration and we demonstrated that their inhibition prevented tumor recurrence in our model.

Although advanced prostate cancer patients respond very well to front-line androgen deprivation, failure to hormonal therapy most often occurs after a median time of 18-24 months. The care of castration-resistant prostate cancer (CRPC) has significantly evolved over the past decade, with the onset of first-line therapy with docetaxel. Although numerous therapy schedules have been investigated alongside docetaxel, in either first-line or salvage therapy, results were dismal. However, CRPC chemotherapy is currently evolving, with, on the one hand, new agents targeting androgen metabolism and, on the other hand, significant progress in chemotherapy drugs, particularly for second-line therapy. The aim of the present review is to describe the current treatments for CRPC chemotherapy alongside their challengers that might shortly become new standards. In this article, we discuss the most recent data from clinical trials to provide the reader with a comprehensive, state-of-the-art overview of CRPC chemotherapy and hormonal therapy., (Copyright © 2011 S. Karger AG, Basel.)

Advanced prostate cancer (PCa) has emerged as a public health concern due to population aging. Although androgen deprivation has proven efficacy in this condition, most advanced PCa patients will have to face failure of androgen deprivation as a treatment. Mutations in the androgen receptor (AR) from tumor cells have been shown to induce androgen independency both in PCa cell lines and in the clinic. We have investigated the molecular events leading to androgen independency in the 22Rv1 cell line, a commonly used preclinical model of PCa. Besides AR mutants that have been described so far, including nonsense mutations, recent data have focused on AR pre-mRNA aberrant splicing as a new mechanism leading to constitutively active truncated AR variants. In this article, we describe two novel variants arising from aberrant splicing of AR pre-mRNA, characterized by long mRNA transcripts that encode truncated, constitutively active proteins. We also describe several new nonsense mutants that share ligand independency and transcriptional activity. Finally, we show that alongside these mutants, 22Rv1 cells also express a mutant AR lacking exon 3 tandem duplication, a major feature of this cell line. By describing unreported AR mutants in the 22Rv1 cell line, our data emphasize the complexity and heterogeneity of molecular events that occur in preclinical models, and supposedly in the clinic. Future work on the 22Rv1 cell line should take into account the concomitant expression of various AR mutants.

Lack of hormone dependency in prostate cancers is an irreversible event that occurs through generation of genomic instability induced by androgen deprivation. Indeed, the cytogenetic profile of hormone-dependent (HD) prostate cancer remains stable as long as it received a hormone supply, whereas the profile of hormone-independent (HID) variants acquired new and various alterations. This is demonstrated here using a HD xenografted model of a human prostate cancer, PAC120, transplanted for 11 years into male nude mice and 4 HID variants obtained by surgical castration. Cytogenetic analysis, done by karyotype, FISH, CGH and array-CGH, shows that PAC120 at early passage presents numerous chromosomal alterations. Very few additional alterations were found between the 5th and 47th passages, indicating the stability of the parental tumor. HID variants largely maintained the core of chromosomal alterations of PAC120 - losses at 6q, 7p, 12q, 15q and 17q sites. However, each HID variant displayed a number of new alterations, almost all being specific to each variant and very few shared by all. None of the HID had androgen receptor mutations. Our study indicates that hormone castration is responsible for genomic instability generating new cytogenetic abnormalities susceptible to alter the properties of cancer cell associated with tumor progression, such as increased cell survival and ability to metastasize.

The androgen receptor (AR) signaling pathway plays an important role during the development of the normal prostate gland, but also during the progression of prostate cancer on androgen ablation therapy. Mutations in the AR gene emerge to keep active the AR signaling pathway and to support prostate cancer cells growth and survival despite the low levels of circulating androgens. Indeed, mutations affecting the ligand binding domain (LBD) of the AR have been shown to generate so-called "promiscuous" receptors that present widened ligand specificity and allow the stimulation of these receptors by a larger spectrum of endogenous hormones. Another class of mutations, arising in the amino-terminal domain (NTD) of the receptor, modulate AR interactions with coregulators involved in cell proliferation regulation. Besides characteristics of these well-known types of mutations, the properties of other classes of AR mutants recently described in prostate cancer are currently under investigation. Most interestingly, in addition to their potential role in the mechanisms which allow prostate cancer cells to escape androgen ablation therapy, data suggest that certain AR mutations are present early in the natural history of the disease and may play a role in many aspects of prostate cancer progression. Surprisingly, singular truncated AR devoid of their carboxy-terminal end (CTE) region seem to exert specific paracrine effects and to induce a clonal cooperation with neighboring prostate cancer cells, which may facilitate both the invasion and metastasis processes. In this article, we review the functional properties of different classes of AR mutants and their potential impact on the natural history of prostate cancer. Hum Mutat 0, 1-14, 2008. (c) 2008 Wiley-Liss, Inc., ((c) 2008 Wiley-Liss, Inc.)

Abstract Several neurodegenerative diseases, including Kennedy's disease (KD), are associated with misfolding and aggregation of polyglutamine (polyQ)-expansion proteins. KD is caused by a polyQ-expansion in the androgen receptor (AR), a key player in male sexual differentiation. Interestingly, KD patients often show signs of mild-to-moderate androgen insensitivity syndrome (AIS) resulting from AR dysfunction. Here, we used the yeast Saccharomyces cerevisiae to investigate the molecular mechanism behind AIS in KD. Upon expression in yeast, polyQ-expanded N-terminal fragments of AR lacking the hormone binding domain caused a polyQ length-dependent growth defect. Interestingly, while AR fragments with 67 Q formed large, SDS-resistant inclusions, the most pronounced toxicity was observed upon expression of 102 Q fragments which accumulated exclusively as soluble oligomers in the 100-600 kDa range. Analysis using a hormone-dependent luciferase reporter revealed that full-length polyQ-expanded AR is fully functional in transactivation, but becomes inactivated in the presence of the corresponding polyQ-expanded N-terminal fragment. Furthermore, the greatest impairment of AR activity was observed upon interaction of full-length AR with soluble AR fragments. Taken together, our results suggest that soluble polyQ-containing fragments bind to full-length AR and inactivate it, thus providing insight into the mechanism behind AIS in KD and possibly other polyglutamine diseases, such as Huntington's disease.

Mutations in the human androgen receptor (AR) gene that lead to C-terminus truncated AR variants are frequently detected in prostate cancer (PC). These AR variants lack both the ligand-binding domain (LBD) and the AF-2 region. The aim of this study was to delineate the alternative mechanisms that lead to the activation of such AR variants as they are unresponsive to hormone stimulation, and to outline consequences of the loss of the LBD/AF-2 region on their functional properties. By using an MMTV-luciferase reporter construct and LY294002, UO126, or ZD1839, inhibitor of PI3K, MEK1/2, and EGFR signaling pathway respectively, we demonstrated that phosphorylation was required for full transcriptional activities of one these AR variants, the Q640X mutant AR. Western-blot analyses confirmed that these inhibitors affect the phosphorylation status of this AR variant. Furthermore, studies of the intranuclear colocalization of the Q640X AR with cofactors, such as CBP, GRIP-1, and c-Jun, reveal that the transcriptional complex that forms around the mutant AR is different to that formed around the wild type AR. We demonstrated that CBP and c-Jun are highly recruited by the mutant AR, and this leads to an unexpected activation of AP-1, NFAT, and NFkappaB transcriptional activities. Similar enhanced activities of these transcription factors were not observed with the wild type AR. The importance of the LBD/AF-2 for the regulation of AR transcriptional activities, the impact of the presence of such AR variants on PC cells proliferation and survival, and on progression to androgen independence are discussed.

The emergence of mutations in the androgen receptor (AR) gene is a recurrent event during progression of prostate cancer (PCa) on androgen ablation therapy. In this study, we show that nonsense mutations that lead to carboxyl-terminal end truncated ARs are found at high frequency in metastatic PCas. Transcriptional activities of the Q640X mutant AR in the androgen-sensitive LNCaP cell line differ to those of the wild-type AR. Indeed, this mutant AR exhibits strong and ligand-independent transcriptional activities from an artificial promoter construct containing two repeats of androgen-responsive elements, but is inactive on the human PSA gene promoter. Nevertheless, the expression of the Q640X mutant AR in LNCaP cells is accompanied by an increase in the level of PSA protein, and by an increase in the expression of the endogenous AR gene. This enhanced expression of the endogenous AR gene is not limited to the sole transfected cells, but is observed in non-transfected neighboring cells. Additionally, in co-cultures of transfected and non-transfected LNCaP cells, the Q640X mutant AR leads to an unpredicted nuclear localization of the endogenous AR protein in the two cellular populations and this, in the absence of androgen. These data indicate that cells expressing the Q640X mutant AR acquire the property to emit a signal that activates the AR in neighboring cells by a paracrine mechanism and in a ligand-independent manner. Our data strongly support the notion of cooperation among tumor cells in PCa and could be of relevance for the understanding of progression on androgen ablation therapy., ((c) 2007 Wiley-Liss, Inc.)

The androgen receptor (AR) is a ligand-activated transcription factor that displays genomic actions characterized by binding to androgen-response elements in the promoter of target genes as well as nongenomic actions that do not require nuclear translocation and DNA binding. In this study, we report exclusive cytoplasmic actions of a splicing variant of the AR detected in a metastatic prostate cancer. This AR variant, named AR23, results from an aberrant splicing of intron 2, wherein the last 69 nucleotides of the intronic sequence are retained, leading to the insertion of 23 amino acids between the two zinc fingers in the DNA-binding domain. We show that the nuclear entry of AR23 upon dihydrotestosterone (DHT) stimulation is impaired. Alternatively, DHT-activated AR23 forms cytoplasmic and perinuclear aggregates that partially colocalize with the endoplasmic reticulum and are devoid of genomic actions. However, in LNCaP cells, this cytoplasmic DHT-activated AR23 remains partially active as evidenced by the activation of transcription from androgen-responsive promoters, the stimulation of NF-kappaB transcriptional activity and by the decrease of AP-1 transcriptional activity. Our data reveal novel cytoplasmic actions for this splicing AR variant, suggesting a contribution in prostate cancer progression.

Androgen receptor (AR) mutations that modify both the ligand binding and the transactivation capacities of the AR represent one of the mechanisms involved in the transition of prostate cancer (PCa) from androgen-dependent to androgen-independent growth. We use a yeast-based functional assay to detect and analyze mutant ARs in PCa. We report the detection of 2 different mutant ARs within the same metastatic tumour sample harvested in a patient with advanced PCa who had escaped androgen deprivation. Concomitantly to the widely described T877A mutant AR, we identified an additional double mutant AR harboring the nonsense mutation Q640Stop just downstream the DNA binding domain together with the T877A point mutation. This type of mutation, which leads to a c-terminal truncated AR, has not been described yet in PCa. Using luciferase reporter assays we demonstrated that this truncated AR exhibited constitutive transactivation properties. In conclusion, our data suggest that mutation-induced constitutive activation of the AR could be a mechanism used by PCa cells to escape androgen deprivation., (Copyright 2004 Wiley-Liss, Inc.)

Objective: Mutations in the ligand-binding domain of the human androgen receptor (AR) figure among the ways used by prostate adenocarcinoma (PCa) cells to escape androgen dependence. These mutations may broaden the specificity and/or affinity of the AR to other hormones, resulting in inappropriate receptor activation and thus affecting the PCa response to physiological stimuli and hormonal therapies., Design: In order to clarify the impact of these mutations on disease progression and treatment, we have developed a yeast-based functional assay that allows the detection of mutant ARs and the analysis of their transactivation capacities in response to different ligands., Methods: AR cDNA was directly cloned into an expression vector in a yeast strain that carries a reporter gene (ADE2) linked to an androgen-dependent promoter. The expression of the ADE2 gene and consequently the yeast cell growth in a selective medium depleted in adenine depends on the specificity of the AR for the ligand added to the medium., Results: By analysing the transactivation capacities of different AR molecules in response to a broad range of steroid and non-steroid ligands, we have demonstrated that this assay can discriminate among wild-type AR, T877A, C685Y and L701H mutant ARs and that at least 1% of mutant ARs could be detected when mutant and wild-type ARs were mixed at the cDNA level., Conclusions: The data presented here show that this simple AR assay is convenient for the routine detection of mutant ARs in PCa and is also suitable to evaluate the antagonist activities of anti-androgen molecules.

Aim: p53 is the most frequently altered gene in human cancer. It was expected to be the principle marker for chemo/radiosensitivity, resistance, tumor recurrence and ultimate survival, but is no longer considered a universal prognostic factor. Different alterations in the p53 gene have led to conflicting results depending on cell/tissue specificities and on radiation and drug specificities., Methods: We evaluated the properties of isogenic and isophenotypic cell lines from the K1 papillary thyroid carcinoma in which p53 function was disrupted either by mutation (expression of dominant-negative p53, 143(ala)) or by inactivation (expression of human papilloma virus protein HPV16 E6). Their proliferation, their propensity to trigger apoptosis and their survival were analyzed after treatment with cisplatin (CDDP)., Results: Only K1 lines with wild-type p53 had significantly accumulated apoptotic bodies 72 h after treatment. Despite their incapacity to trigger apoptosis in response to CDDP treatment, the survival of K1 cell lines in which p53 expression was altered was not significantly different from the survival of K1 cell lines expressing wild-type p53. In addition, the order of magnitude of resistance of K1 cells in which p53 was mutated was similar to that in which p53 was totally inactivated, although the pathways involved may be different., Conclusions: These results show that the means by which p53 expression is disrupted and the consequence on downstream pathways regulated by p53 deserve to be considered in order to elucidate some apparently conflicting responses of this gene.

In the literature the sensitization of DNA to radiation-induced damage by caffeine has been attributed to an override of the G2/M block. This process was supposed to involve the tumor suppressor gene p53 as it was described that p53 negative cells were more sensitive to checkpoint inhibition by caffeine than the wildtype phenotype. We have recently shown that caffeine does not cause an override of the G2/M block induced by radiation in normal human fibroblasts. We demonstrate here that this also applies to a human transformed cell line, the thyroid carcinoma K1, when submitted to gamma- rays irradiation. Within 9 hr after irradiation over 70% of the cells accumulated in the G2/M phase. This block persisted at 16 hr. In caffeine containing cultures the percentage of cells attaining the G2/M phase was reduced by over 30% at 16 hr. This was reflected in an accumulation of the cells in G1 phase and an inhibition of the S phase traverse. Cell cycle analyses from further time points combined with cell proliferation measurements confirmed these data. These results were independent of p53 status as experiments performed with variant K1 cell lines having defective p53 functions, led to similar conclusions. In addition, caffeine restored a G1 delay after irradiation in the cell lines with abrogated p53 functions. The effects of caffeine undeniably cumulate with damages induced by irradiation but probably by inhibiting DNA repair mechanisms or by intervening with purine and pyrimidine metabolisms and not by causing a G2/M block override., (Copyright 2001 Wiley-Liss, Inc.)

p53 mutations are found in about 70% of human cancers. In order to evaluate the role of these mutations in response to chemotherapeutic agents, it is important to distinguish between p53 response to DNA-damaging agents in normal and in tumour cells. Here, using normal human fibroblasts (NHFs), we show that cisplatin and UV radiation induce G2/M arrest which is temporally linked to p53-protein induction. To study the contribution of p53 to this G2/M arrest, we inhibited p53 induction in NHFs using p53 anti-sense oligonucleotides. Following exposure of NHFs to UV radiation, the inhibition of p53-protein induction leads to a greater accumulation of cells in the G2/M phase, but also to a decreased fraction of cells in the G1 phase. We propose that p53 does not induce G2/M arrest directly, and that the extent of this arrest may depend on the fraction of cells that do not stop at the G1 phase following exposure to DNA-damaging agents. Furthermore, inhibition of p53-protein induction leads to increased sensitivity of NHFs to UV radiation. These results suggest that inhibition of p53 protein enhances sensitivity to DNA-damaging agents in normal human cells.

The aim of this work was to evaluate the effects of SR 25989, a member of the thienopyridine family devoid of antiplatelet activity but possessing anti-angiogenic properties, on the regulation of proteins involved in matrix remodeling during wound healing or tumor progression. Human endothelial cells grown in the presence of SR 25989 showed moderate increases in the production of activators (tissue plasminogen activator and urokinase) and one inhibitor (plasminogen activator inhibitor type 1) of fibrinolysis, together with a significant rise in intracellular thrombospondin-1. SR 25989 induced a similar increase in thrombospondin-1 in human foreskin fibroblasts. This over-expression of thrombospondin-1 was correlated to a decrease in cell density. A concomitant increase in the tumor suppressor gene protein p53 was observed in endothelial cells and in fibroblasts, in which the slowing down of proliferation could be related to an accumulation of cells in the S and G2/M phases of the cell cycle. Northern blot analysis revealed a temporary rise in thrombospondin-1 transcripts, followed by a decrease along with a moderate increase in p53 transcripts. Thus the anti-angiogenic properties of SR 25989 appear to result from an upregulation of thrombospondin-1 which is possibly mediated by p53. The thienopyridine SR 25989 could therefore be a good candidate for adjuvant anti-angiogenic therapy in cancer.