The Mll gene is a member of the mammalian trithorax group, involved with the antagonistic Polycomb group in epigenetic regulation of homeotic genes. MLL contains a highly conserved SET domain also found in various chromatin proteins. In this study, we report that mice in which this domain was deleted by homologous recombination in ES cells (⌬SET) exhibit skeletal defects and altered transcription of particular Hox genes during development. Chromatin immunoprecipitation and bisulfite sequencing analysis on developing embryo tissues demonstrate that this change in gene expression is associated with a dramatic reduction in histone H3 Lysine 4 monomethylation and DNA methylation defects at the same Hox loci. These results establish in vivo that the major function of Mll is to act at the chromatin level to sustain the expression of selected target Hox genes during embryonic development. These observations provide previously undescribed evidence for the in vivo relationship and SET domain dependence between histone methylation and DNA methylation on MLL target genes during embryonic development.histone methyltransferase ͉ MLL-SET domain ͉ homeotic transformations T he control of cell identity during development is specified, in large part, by the unique expression patterns of multiple homeobox-containing (Hox) genes in specific segments of the embryo (1). The trithorax and polycomb groups (trx-G and PcG) were identified for their role in faithfully maintaining the transcriptional states of these key developmental regulators, providing an epigenetic mechanism of cellular memory (2-4).The gene expression maintenance function of the trxG and PcG proteins is highly conserved. Mixed lineage leukemia (Mll), a human homolog of Drosophila trithorax and a member of the trxG family, was identified first for its involvement in chromosomal translocations associated with lymphoid and myeloid acute leukemia in infants and adults (5, 6). Mll encodes a 3,969-aa nuclear protein with multiple domains, including three AT-hook motifs, a DNA methyltransferase homology domain (DNMT) in the aminoterminal half of the protein, a central zinc finger (PHD) region, and a highly conserved 130-aa carboxyl-terminal SET domain. The MLL protein was shown to be proteolytically processed into two portions (MLL N and MLL C ) with antagonistic transcriptional effector properties, that reassociate and stabilize each other (7-9). The MLL protein is critical for proper regulation of the Hox genes during embryonic development (10). In Mll null mutant mice (MllϪ͞Ϫ), Hox gene expression is correctly initiated but is not sustained as the function of Mll becomes necessary (11), leading to embryonic lethality.It is strongly believed that maintenance of the transcriptional status of target genes by PcG and trxG proteins is achieved through chromatin modifications (12). The structure similarity between some trxG͞PcG and suppressors or enhancers of position effect variegation (PEV) further substantiates this point. One of the most remarkable shared domains within th...
BackgroundThe INK4/ARF locus encodes three tumor suppressor genes (p15Ink4b, Arf and p16Ink4a) and is frequently inactivated in a large number of human cancers. Mechanisms regulating INK4/ARF expression are not fully characterized.Principal FindingsHere we show that in young proliferating embryonic fibroblasts (MEFs) the Polycomb Repressive Complex 2 (PRC2) member EZH2 together with PRC1 members BMI1 and M33 are strongly expressed and localized at the INK4/ARF regulatory domain (RD) identified as a DNA replication origin. When cells enter senescence the binding to RD of both PRC1 and PRC2 complexes is lost leading to a decreased level of histone H3K27 trimethylation (H3K27me3). This loss is accompanied with an increased expression of the histone demethylase Jmjd3 and with the recruitment of the MLL1 protein, and correlates with the expression of the Ink4a/Arf genes. Moreover, we show that the Polycomb protein BMI1 interacts with CDC6, an essential regulator of DNA replication in eukaryotic cells. Finally, we demonstrate that Polycomb proteins and associated epigenetic marks are crucial for the control of the replication timing of the INK4a/ARF locus during senescence.ConclusionsWe identified the replication licencing factor CDC6 as a new partner of the Polycomb group member BMI1. Our results suggest that in young cells Polycomb proteins are recruited to the INK4/ARF locus through CDC6 and the resulting silent locus is replicated during late S-phase. Upon senescence, Jmjd3 is overexpressed and the MLL1 protein is recruited to the locus provoking the dissociation of Polycomb from the INK4/ARF locus, its transcriptional activation and its replication during early S-phase. Together, these results provide a unified model that integrates replication, transcription and epigenetics at the INK4/ARF locus.
Resistance to castration is a crucial issue in the treatment of metastatic prostate cancer. Kinase inhibitors (KIs) have been tested as potential alternatives, but none of them are approved yet. KIs are subject of extensive metabolism at both the hepatic and the tumor level. Here, we studied the role of PXR (Pregnane X Receptor), a master regulator of metabolism, in the resistance to KIs in a prostate cancer setting. We confirmed that PXR is expressed in prostate tumors and is more frequently detected in advanced forms of the disease. We showed that stable expression of PXR in 22Rv1 prostate cancer cells conferred a resistance to dasatinib and a higher sensitivity to erlotinib, dabrafenib, and afatinib. Higher sensitivity to afatinib was due to a ~ 2-fold increase in its intracellular accumulation and involved the SLC16A1 transporter as its pharmacological inhibition by BAY-8002 suppressed sensitization of 22Rv1 cells to afatinib and was accompanied with reduced intracellular concentration of the drug. We found that PXR could bind to the SLC16A1 promoter and induced its transcription in the presence of PXR agonists. Together, our results suggest that PXR could be a biomarker of response to kinase inhibitors in castration-resistant prostate cancers.
BackgroundCOU-AA-301 trial has proved that abiraterone acetate (AA), a selective inhibitor of androgen biosynthesis, improved overall survival (OS) of patients with metastatic castration resistant prostate cancer (mCRPC) after a first line of docetaxel. Based on this result, a Temporary Authorization for Use (TAU) was performed between December 2010 and July 2011 to provide patients with mCRPC the opportunity to receive AA before its commercialization. The aim of this study was to evaluate safety and efficacy of AA treatment in this TAU.MethodsBetween December 2010 and July 2011, we conducted an ambispective, multicentric cohort study and investigated data from 20 centres participating to the AA TAU for patients presenting mCRPC and already treated by a first line of chemotherapy (CT). Statistical analyses of the data were performed using the Stata software v13 to identify predictive and prognostic factors.ResultsAmong the 408 patients, 306 were eligible with a follow-up at 3 years. Median OS was 37.1 months from beginning of CT and 14.6 months from AA introduction. 211 patients (69%) received ≥ 3 months of AA and 95 patients (31%) were treated less than 3 months. In the multivariate analyses, duration of AA was significantly correlated with PSA decrease at 3 months. Additionally, shorter time under AA treatment, presence of multiple sites of metastasis and previous hormonal treatment duration were three independent factors associated with poorer OS. At the time of analysis ten patients were still under treatment for more than 3 years.ConclusionsBiochemical response monitored by PSA changes at 3 months is a strong predictive factor for AA treatment duration. Some high responders’ patients could beneficiate from AA for more than 3 years.
Multiple sclerosis (MS) is an inflammatory demyelinating disease often characterized by remission and relapse periods occurring at irregular intervals after an initial attack (clinically isolated syndrome) and followed by a gradual progression of disability. Clinical symptoms, magnetic resonance imaging and abnormalities in cerebrospinal fluid (CSF) immunoglobulin profile allow diagnosis with a good sensitivity. However, current biomarkers lack specificity or have poor individual prognostic value. To identify novel candidate biomarkers of MS, we analysed 1) the CSF proteome from symptomatic controls and patients with clinically isolated syndrome or remitting-relapsing multiple sclerosis (n=40), and 2) changes in oligodendrocyte secretome upon proinflammatory or pro-apoptotic treatment. Proteins exhibiting differences in abundance in both studies were combined with previously described MS biomarkers to build a list of 87 proteins that were quantified by parallel reaction monitoring (PRM) in CSF samples from a new cohort comprising symptomatic controls and MS patients at different disease stages (n=60). The eleven proteins that passed this qualification step were subjected to a new PRM assay from a larger cohort (n=158) comprising patients with MS at different disease stages or with other inflammatory or non-inflammatory neurological disorders. Collectively, these studies identified a biomarker signature of MS that might improve MS diagnosis and prognosis. These include the oligodendrocyte precursor cell proteoglycan Syndecan-1, which was more efficient than previously described biomarkers to discriminate MS from other inflammatory and non-inflammatory neurological disorders.
Les génomes sont continuellement endommagés par des stress environnementaux, et, dans des cellules se divisant, par des erreurs de la réplication de l'ADN. Selon le niveau et le type de dégâts, les cellules peuvent tenter de réparer le génome, ou mourir. Dans des cellules se divisant, l'un des risques majeurs est l'apparition de mutations, qui sont produites par des échecs ou des erreurs de la réparation. Si une mutation confère un avantage de survie/prolifération, ou induit une instabilité génomique, alors les risques de développer des cancers sont très élevés. Les organismes complexes ont développé au moins deux mécanismes cellulaires pour inhiber la prolifération de cellules présentant des risques de transformation : l'apoptose ou mort cellulaire programmée et la sénes-cence cellulaire. La sénescence cellulaire arrête de façon irréversible la croissance cellulaire et est une barrière majeure que les cellules doivent surmonter pour progresser vers un état tumoral. Cependant, tandis que l'apoptose élimine des cellules potentiellement cancéreuses, la sénescence réplicative bloque irréversiblement leur prolifération. Les cellules sénescentes peuvent êtres identifiées par plusieurs caractéristiques : (1) elles expriment spécifiquement la β-galactosidase endogène à pH 6 [1, 2] ; (2) elles sont bloquées en phase G1 du cycle ; (3) leur nucléole est fragmenté [3,4]. Des découvertes récentes ont permis de nouvelles avancées sur les causes de sénescence cellulaire, la complexité du phénotype de sénescence et les consé-quences potentielles de la sénescence cellulaire pour l'organisme. La sénescence réplicative in vitroLa sénescence cellulaire a été décrite, il y a plus de 40 ans, comme un processus qui empêche des fibroblastes humains normaux de se diviser indéfiniment en culture. La décennie passée nous a appris que ce processus, connu maintenant sous le nom de sénescence répli-cative, est induit par le raccourcissement des télomères. Cependant, il a été montré récemment que des stimulus n'ayant peu ou pas d'impact sur les télomères induisent aussi des cellules normales à arrêter leur croissance avec un phénotype de sénescence. Ces stimulus incluent des dommages de l'ADN, le remodelage de la chromatine et des signaux mitogènes forts. Ainsi, la sénescence réplicative est un exemple d'un processus physiologique plus général, que nous appellerons ici « sénescence cellulaire ». La sénescence cellulaire entraîne de profonds changements de l'expression des gènes, dont seuls quelquesuns sont impliqués dans l'arrêt de la prolifération. Ainsi, quelques cellules (fibroblastes et lymphocytes T humains) deviennent aussi résistantes à la mort apoptotique. De plus, toutes les cellules montrent des changements de fonction quand elles deviennent sénescen-tes et restent métaboliquement actives. Les acteurs moléculaires de la sénescenceAu plan moléculaire, on sait qu'un locus particulier dans le génome des mammifères, le locus Ink4a/ARF, lorsqu'il > La division cellulaire est essentielle pour la survie des organismes multicellulaires qui...
264 Background: COU-AA-301 trial has proved that abiraterone acetate (AA), a selective inhibitor of androgen biosynthesis, improved overall survival (OS) of patients with metastatic castration resistant prostate cancer (mCRPC) after a first line of docetaxel. Based on this result, a temporary use authorisation (TUA) was performed between December 2010 and July 2011 to provide patients with mCRPC the opportunity to receive AA before its commercialization. The aim of this study was to evaluate safety and efficacy of AA treatment in this TUA. Methods: Between December 2010 and July 2011, we conducted an ambispective, multicentric cohort study and investigated data from 20 centres participating to the AA TUA for patients presenting mCRPC and already treated by a first line of chemotherapy (CT). Statistical analyses of the data were performed using the Stata software v13 to identify predictive and prognostic factors. Results: Among the 408 patients, 306 were eligible with a follow-up at 3 years. Median OS was 37.1 months from beginning of CT and 14.6 months from AA introduction. 211 patients (69%) received ≥ 3 months of AA and 95 patients (31%) were treated less than 3 months. In the multivariate analyses, duration of AA was significantly correlated with PSA decrease at 3 months. Additionally, shorter time under AA treatment, presence of multiple sites of metastasis and previous hormonal treatment duration were three independent factors associated with poorer OS. At the time of analysis ten patients were still under treatment for more than 3 years. Conclusions: Biochemical response monitored by PSA changes at 3 months is a strong predictive factor for AA treatment duration. Some high responders’ patients could beneficiate from AA for more than 3 years.
Background and aimsMultiple sclerosis (MS) is associated with osteoporosis, possibly due to neurological disability and decreased calcium intake. The objective of this study was to evaluate the efficacy of a personalized nutritional advice program by a dietitian compared to the delivery of a standard advice form to optimize dietary calcium intake in outpatients with MS.MethodsWe performed a randomized, controlled, parallel trial comparing the efficacy of a personalized dietary advice (PDA) program to standard advice form (SAF) to increase daily calcium intake in MS patients. The study population was composed by patients with relapsing-remitting MS aged 18–69 years old. PDA program consisted in dietary advice delivered by a dietitian at baseline, 1 month, and 3 months. Calcium and nutrient intake in patients from both groups was evaluated at baseline and 6 months using a dietary survey.ResultsOf the 194 patients screened for inclusion, 182 patients were included (79% female, median age of 42 years, and median EDSS of 2.0), and randomized to SAF (n = 92) or PDA (n = 90). At 6 months, median calcium intake increased by 241 mg/day in the PDA group and decreased by 120 mg/day in the SAF group (p < 0.0001). However, the median calcium intake was 947 mg/day in the SAF group and 778 mg/day in the PDA group at baseline (p = 0.0077), potentially favoring the effect of dietary advice. Complementary analyses focusing on patients with insufficient calcium intakes at baseline revealed comparable values in both groups (p = 0.69). Of those, patients included in the PDA group obtained significantly higher calcium intakes at 6 months than patients from the SAF group (p = 0.0086) independently of EDSS, PASAT, HADS and EQ-5D scores.ConclusionThis work shows the efficacy of dietary management based on personalized advice program over 3 months to durably increase calcium consumption in MS patients with insufficient calcium intake.Clinical trial registrationclinicaltrials.gov, identifier NCT02664623.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.