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  • Health Reference Center Academic (Gale)  (43)
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  • 1
    Language: English
    In: The Journal of clinical investigation, April 2011, Vol.121(4), pp.1344-8
    Description: Pilocytic astrocytoma (PA) is the most common type of primary brain tumor in children and the second most frequent cancer in childhood. Children with incompletely resected PA represent a clinically challenging patient cohort for whom conventional adjuvant therapies are only moderately effective. This has produced high clinical demand for testing of new molecularly targeted treatments. However, the development of new therapeutics for PA has been hampered by the lack of an adequate in vivo tumor model. Recent studies have identified activation of MAPK signaling, mainly by oncogenic BRAF activation, as a hallmark genetic event in the pathogenesis of human PA. Using in vivo retroviral somatic gene transfer into mouse neural progenitor cells, we have shown here that ectopic expression of the activated BRAF kinase domain is sufficient to induce PA in mice. Further in vitro analyses demonstrated that overexpression of activated BRAF led to increased proliferation of primary mouse astrocytes that could be inhibited by treatment with the kinase inhibitor sorafenib. Our in vivo model for PA shows that the activated BRAF kinase domain is sufficient to induce PA and highlights its role as a potential therapeutic target.
    Keywords: Astrocytoma -- Etiology ; Brain Neoplasms -- Etiology ; Proto-Oncogene Proteins B-Raf -- Genetics
    ISSN: 00219738
    E-ISSN: 1558-8238
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  • 2
    In: International Journal of Cancer, 01 February 2014, Vol.134(3), pp.703-716
    Description: Based on extensive pre‐clinical studies, the oncolytic parvovirus H‐1 (H‐1PV) is currently applied to patients with recurrent glioblastoma in a phase I/IIa clinical trial (ParvOryx01, NCT01301430). Cure rates of about 40% in pediatric high‐risk medulloblastoma (MB) patients also indicate the need of new therapeutic approaches. In order to prepare a future application of oncolytic parvovirotherapy to MB, the present study preclinically evaluates the cytotoxic efficacy of H‐1PV on MB cells and characterizes cellular target genes involved in this effect. Six MB cell lines were analyzed by whole genome oligonucleotide microarrays after treatment and the results were matched to known molecular and cytogenetic risk factors. In contrast to non‐transformed infant astrocytes and neurons, in five out of six MB cell lines lytic H‐1PV infection and efficient viral replication could be demonstrated. The cytotoxic effects induced by H‐1PV were observed at LD50s below 0.05 p. f. u. per cell indicating high susceptibility. Gene expression patterns in the responsive MB cell lines allowed the identification of candidate target genes mediating the cytotoxic effects of H‐1PV. H‐1PV induced down‐regulation of key regulators of early neurogenesis shown to confer poor prognosis in MB such as ZIC1, FOXG1B, MYC, and NFIA. In MB cell lines with genomic amplification of MYC, expression of MYC was the single gene most significantly repressed after H‐1PV infection. H‐1PV virotherapy may be a promising treatment approach for MB since it targets genes of functional relevance and induces cell death at very low titers of input virus. What's new? Medulloblastoma, the most frequent pediatric brain cancer, causes death in about 60 percent of high‐risk patients, and so there is a major need for novel, highly effective therapies. One therapy of interest is parvovirus H‐1 (H‐1PV), which was found in this study to produce marked cytotoxic effects in six medulloblastoma cell lines. Gene expression profiling revealed that H‐1PV infection causes down‐regulation of key regulatory genes involved in early neurogenesis, with significant repression of . The master regulators affected may represent putative direct or indirect H‐1PV target genes.
    Keywords: Medulloblastoma ; Oncolytic Virus ; Parvovirus H‐1pv ; Cellular Targets ; Myc ; Master Regulators Of Neurogenesis
    ISSN: 0020-7136
    E-ISSN: 1097-0215
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  • 3
    Language: English
    In: International Journal of Cancer, 01 May 2013, Vol.132(9), pp.2200-2208
    Description: Inhibition of histone deacetylase (HDAC) activity as stand‐alone or combination therapy represents a promising therapeutic approach in oncology. The pan‐ or class I HDAC inhibitors (HDACi) currently approved or in clinical studies for oncology give rise to dose‐limiting toxicities, presumably because of the inhibition of several HDACs. This could potentially be overcome by selective blockade of single HDAC family members. Here we report that HDAC11, the most recently identified zinc‐dependent HDAC, is overexpressed in several carcinomas as compared to corresponding healthy tissues. HDAC11 depletion is sufficient to cause cell death and to inhibit metabolic activity in HCT‐116 colon, PC‐3 prostate, MCF‐7 breast and SK‐OV‐3 ovarian cancer cell lines. The antitumoral effect induced can be mimicked by enforced expression of a catalytically impaired HDAC11 variant, suggesting that inhibition of the enzymatic activity of HDAC11 by small molecules could trigger the desired phenotypic changes. HDAC11 depletion in normal cells causes no changes in metabolic activity and viability, strongly suggesting that tumor‐selective effects can be achieved. Altogether, our data show that HDAC11 plays a critical role in cancer cell survival and may represent a novel drug target in oncology. What's new? Histone deacetylase (HDAC) enzymes influence the regulation of numerous cellular processes, and their inhibition by small molecules has been shown to provide benefits against multiple cancer types. Here, HDAC11, a recently identified member of the HDAC family, was found to play an important role in the control of proliferation and survival pathways in several carcinoma cell lines. The high incidence of the tumors represented suggests that HDAC11 could be a valuable drug target in oncology.
    Keywords: Chromatin Modulation ; Targeted Therapy ; Histone Deacetylase ; Colon Cancer ; Prostate Cancer
    ISSN: 0020-7136
    E-ISSN: 1097-0215
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  • 4
    In: Nature, 2014, Vol.510(7506), p.537
    Description: Epigenetic alterations, that is, disruption of DNA methylation and chromatin architecture, are now acknowledged as a universal feature of tumorigenesis. Medulloblastoma, a clinically challenging, malignant childhood brain tumour, is no exception. Despite much progress from recent genomics studies, with recurrent changes identified in each of the four distinct tumour subgroups (WNT-pathway-activated, SHH-pathway-activated, and the less-well-characterized Group 3 and Group 4), many cases still lack an obvious genetic driver. Here we present whole-genome bisulphite-sequencing data from thirty-four human and five murine tumours plus eight human and three murine normal controls, augmented with matched whole-genome, RNA and chromatin immunoprecipitation sequencing data. This comprehensive data set allowed us to decipher several features underlying the interplay between the genome, epigenome and transcriptome, and its effects on medulloblastoma pathophysiology. Most notable were highly prevalent regions of hypomethylation correlating with increased gene expression, extending tens of kilobases downstream of transcription start sites. Focal regions of low methylation linked to transcription-factor-binding sites shed light on differential transcriptional networks between subgroups, whereas increased methylation due to re-normalization of repressed chromatin in DNA methylation valleys was positively correlated with gene expression. Large, partially methylated domains affecting up to one-third of the genome showed increased mutation rates and gene silencing in a subgroup-specific fashion. Epigenetic alterations also affected novel medulloblastoma candidate genes (for example, LIN28B), resulting in alternative promoter usage and/or differential messenger RNA/microRNA expression. Analysis of mouse medulloblastoma and precursor-cell methylation demonstrated a somatic origin for many alterations. Our data provide insights into the epigenetic regulation of transcription and genome organization in medulloblastoma pathogenesis, which are probably also of importance in a wider developmental and disease context.
    Keywords: Gene Expression Regulation, Neoplastic ; Gene Silencing ; DNA Methylation -- Genetics ; Medulloblastoma -- Genetics ; Sequence Analysis, DNA -- Methods;
    ISSN: 0028-0836
    E-ISSN: 1476-4687
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  • 5
  • 6
    In: Nature, 2012, Vol.482(7384), p.226
    Description: Glioblastoma multiforme (GBM) is a lethal brain tumour in adults and children. However, DNA copy number and gene expression signatures indicate differences between adult and paediatric cases (1-4). To explore the genetic events underlying this distinction, we sequenced the exomes of 48 paediatric GBM samples. Somatic mutations in the H3.3-ATRX-DAXX chromatin remodelling pathway were identified in 44% of tumours (21/48). Recurrent mutations in H3F3A, which encodes the replication-independent histone 3 variant H3.3, were observed in 31% of tumours, and led to amino acid substitutions at two critical positions within the histone tail (K27M, G34R/G34V) involved in key regulatory post-translational modifications. Mutations in ATRX([alpha]-thalassaemia/mental retardation syndrome X-linked) (5) and DAXX (death-domain associated protein), encoding two subunits of a chromatin remodelling complex required for H3.3 incorporation at pericentric heterochromatin and telomeres (6,7), were identified in 31% of samples overall, and in 100% of tumours harbouring a G34R or G34V H3.3 mutation. Somatic TP53 mutations were identified in 54% of all cases, and in 86% of samples with H3F3A and/or ATRX mutations. Screening of a large cohort of gliomas of various grades and histologies (n = 784) showed H3F3A mutations to be specific to GBM and highly prevalent in children and young adults. Furthermore, the presence of H3F3A/ATRX-DAXX/TP53 mutations was strongly associated with alternative lengthening of telomeres and specific gene expression profiles. This is, to our knowledge, the first report to highlight recurrent mutations in a regulatory histone in humans, and our data suggest that defects of the chromatin architecture underlie paediatric and young adult GBM pathogenesis.
    Keywords: Gene Mutation -- Research ; Dna -- Research ; Dna -- Physiological Aspects ; Glioblastomas -- Genetic Aspects ; Glioblastomas -- Research ; Tumor Proteins -- Physiological Aspects ; Tumor Proteins -- Research;
    ISSN: 0028-0836
    E-ISSN: 14764687
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  • 7
    In: Biometrical Journal, January 2014, Vol.56(1), pp.86-106
    Description: Adaptive designs were originally developed for independent and uniformly distributed ‐values. There are trial settings where independence is not satisfied or where it may not be possible to check whether it is satisfied. In these cases, the test statistics and ‐values of each stage may be dependent. Since the probability of a type I error for a fixed adaptive design depends on the true dependence structure between the ‐values of the stages, control of the type I error rate might be endangered if the dependence structure is not taken into account adequately. In this paper, we address the problem of controlling the type I error rate in two‐stage adaptive designs if any dependence structure between the test statistics of the stages is admitted (worst case scenario). For this purpose, we pursue a copula approach to adaptive designs. For two‐stage adaptive designs without futility stop, we derive the probability of a type I error in the worst case, that is for the most adverse dependence structure between the ‐values of the stages. Explicit analytical considerations are performed for the class of inverse normal designs. A comparison with the significance level for independent and uniformly distributed ‐values is performed. For inverse normal designs without futility stop and equally weighted stages, it turns out that correcting for the worst case is too conservative as compared to a simple Bonferroni design.
    Keywords: Adaptive Designs ; Copulas ; Dependent Test Statistics ; Inflation Of Type I Error Rate ; Inverse Normal Method
    ISSN: 0323-3847
    E-ISSN: 1521-4036
    Source: John Wiley & Sons, Inc.
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  • 8
    Language: English
    In: PLoS ONE, June 28, 2016, Vol.11(6)
    Description: Background Everolimus, a mammalian target of rapamycin (mTOR) inhibitor, has demonstrated efficacy in treating subependymal giant cell astrocytomas (SEGAs) and other manifestations of tuberous sclerosis complex (TSC). However, long-term use of mTOR inhibitors might be necessary. This analysis explored long-term efficacy and safety of everolimus from the conclusion of the EXIST-1 study (NCT00789828). Methods and Findings EXIST-1 was an international, prospective, double-blind, placebo-controlled phase 3 trial examining everolimus in patients with new or growing TSC-related SEGA. After a double-blind core phase, all remaining patients could receive everolimus in a long-term, open-label extension. Everolimus was initiated at a dose (4.5 mg/m.sup.2 /day) titrated to a target blood trough of 5-15 ng/mL. SEGA response rate (primary end point) was defined as the proportion of patients achieving confirmed [greater than or equal to]50% reduction in the sum volume of target SEGA lesions from baseline in the absence of worsening nontarget SEGA lesions, new target SEGA lesions, and new or worsening hydrocephalus. Of 111 patients (median age, 9.5 years) who received [greater than or equal to]1 dose of everolimus (median duration, 47.1 months), 57.7% (95% confidence interval [CI], 47.9-67.0) achieved SEGA response. Of 41 patients with target renal angiomyolipomas at baseline, 30 (73.2%) achieved renal angiomyolipoma response. In 105 patients with [greater than or equal to]1 skin lesion at baseline, skin lesion response rate was 58.1%. Incidence of adverse events (AEs) was comparable with that of previous reports, and occurrence of emergent AEs generally decreased over time. The most common AEs ([greater than or equal to]30% incidence) suspected to be treatment-related were stomatitis (43.2%) and mouth ulceration (32.4%). Conclusions Everolimus use led to sustained reduction in tumor volume, and new responses were observed for SEGA and renal angiomyolipoma from the blinded core phase of the study. These findings support the hypothesis that everolimus can safely reverse multisystem manifestations of TSC in a significant proportion of patients. Trial Registration ClinicalTrials.gov NCT00789828
    Keywords: Everolimus – Research ; Everolimus – Health Aspects ; Tuberous Sclerosis – Research ; Tuberous Sclerosis – Drug Therapy ; Tuberous Sclerosis – Patient Outcomes ; Astrocytomas – Research ; Astrocytomas – Drug Therapy
    ISSN: 1932-6203
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  • 9
    In: Nature, 2001, Vol.411(6840), p.909
    Description: Life on Earth depends on photosynthesis, the conversion of light energy from the sun to chemical energy. In plants, green algae, and cyanobacteria, this process is driven by the cooperation of two large protein-cofactor complexes, photosystems I and II, which are located in the thylakoid photosynthetic membranes. The crystal structure of photosystem I from the thermophilic cyanobacterium Synechococcus elongatus described in this paper provides a picture at atomic detail of 12 protein subunits and 127 cofactors comprising 96 chlorophylls, two phylloquinones, three Fe4S4 clusters, 22 carotenoids, four lipids, a putative Ca(2+) ion and 201 water molecules. The structural information on the proteins and cofactors and their interactions provides a basis for understanding how the high efficiency of photosystem I in light capturing and electron transfer is achieved. (Author)
    Keywords: Algae ; Photosynthesis ; Crystal Structure ; Proteins ; Molecular Biology ; Chlorophylls ; Quinones ; Molecular Clusters ; Carotene ; Lipids ; Calcium ; Water ; Electron Transfer ; LIFE Sciences (General) (Ah) ; Article;
    ISSN: 0028-0836
    E-ISSN: 1476-4687
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  • 10
    In: Nature, 2014
    Description: Medulloblastoma is a highly malignant paediatric brain tumour currently treated with a combination of surgery, radiation and chemotherapy, posing a considerable burden of toxicity to the developing child. Genomics has illuminated the extensive intertumoral heterogeneity of medulloblastoma, identifying four distinct molecular subgroups. Group 3 and group 4 subgroup medulloblastomas account for most paediatric cases; yet, oncogenic drivers for these subtypes remain largely unidentified. Here we describe a series of prevalent, highly disparate genomic structural variants, restricted to groups 3 and 4, resulting in specific and mutually exclusive activation of the growth factor independent 1 family proto-oncogenes, GFI1 and GFI1B. Somatic structural variants juxtapose GFI1 or GFI1B coding sequences proximal to active enhancer elements, including super-enhancers, instigating oncogenic activity. Our results, supported by evidence from mouse models, identify GFI1 and GFI1B as prominent medulloblastoma oncogenes and implicate 'enhancer hijacking' as an efficient mechanism driving oncogene activation in a childhood cancer.
    Keywords: Medulloblastoma – Research ; Medulloblastoma – Health Aspects ; DNA Sequencing – Analysis ; Growth Factor Receptors – Analysis;
    ISSN: 0028-0836
    E-ISSN: 14764687
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