1,720,956 research outputs found
Tumor-specific activity of cellular regulatory elements is down-regulated upon insertion into the herpes simplex virus genome
No full textTranscriptional targeting of viral genes is a promising strategy to achieve tumor-specific replication of oncolytic viruses. Due to its natural tropism, herpes simplex virus type 1 (HSV-1) may be an ideal tool for oncolytic therapy of brain tumors such as malignant glioblastoma. To study whether glioma-specific gene expression can be accomplished within the HSV-1 genome, four cellular regulatory elements were exemplarily studied. Whereas the human telomerase reverse transcriptase (hTERT) and survivin promoters and the nestin and vascular endothelial growth factor A (VEGF-A) enhancers displayed pronounced glioma specificity after plasmid transfection, only the nestin enhancer conferred a certain selectivity for glioma cells and notable activity when transferred into the viral genome. The nestin enhancer was also found to be highly useful for tumor cell-specific expression of a therapeutically relevant gene (interleukin-2) when tested in combination with the hTERT or simian virus 40 (SV40) early promoter in the HSV-1 genome. Because activity of the chosen promoter in a tumor is a prerequisite for the successful application of an oncolytic virus, we examined whether the activity of a promoter can be deduced from the amounts of cellular mRNA or protein expressed under its control. We found little correlation between promoter activity and mRNA levels of the corresponding gene, whereas protein expression was more closely related to promoter activity. We conclude that the cellular elements are differently regulated in the viral and cellular genomes. Mechanistic insight into the differential regulation is required to improve and refine the design of transcriptionally targeted HSV vectors. Journal of NeuroVirology (2008) 14, 522-535
A redshifted codon-optimized firefly luciferase is a sensitive reporter for bioluminescence imaging
No full textBioluminescence imaging has evolved as a powerful tool for monitoring biological processes in vivo. As transmission efficiency of light through tissue increases greatly for wavelengths above 600 nm we examined whether a redshifted codon-optimized firefly luciferase (lambda(max) = 615 nm) could be successfully employed as a sensitive reporter in mammalian cells. To this end, unmodified codon-optimized luciferase ( lmax = 557 nm) as well as the red-emitting S284T mutant luciferase were expressed simultaneously in human glioma cells in vitro as well as in quadriceps muscles of mice in vivo. We show here that activity of the redshifted enzyme in human glioma cell culture approached approximately one-fourth of that seen with the unmodified enzyme. In contrast, light emission by the red-emitting luciferase in vivo was generally more efficient than that produced by its unmodified counterpart, most likely due to reduced absorption of red light by tissue. The mean ratio of light emission produced by the redshifted luciferase to that of the unmodified enzyme in vivo was similar to 3. Application of this new redshifted luciferase together with other optical reporters may be of considerable importance to biological research as it allows for imaging of deeper tissues as well as simultaneous monitoring of two molecular events in vitro and in vivo if appropriate filter sets are employed
mRNA expression levels of hypoxia-induced and stem cell-associated genes in human glioblastoma
No full textThe roles of hypoxia-induced and stem cell-associated genes in the development of malignancy and tumour progression are well known. However, there are a limited number of studies analysing the impact of mRNA expression levels of hypoxia-induced and stem cell-associated genes in the tissues of brain tumours and glioblastoma patients. In this study, tumour tissues from patients with glioblastoma multiforme and tumour adjacent tissues were analysed. We investigated mRNA expression levels of hypoxia-inducible factor-la (HIF-1 alpha), hypoxia-inducible factor-2 alpha (HIF-2 alpha), carbonic anhydrase 9 (CA9), vascular endothelial growth factor (VEGF), glucose transporter-1 (GLUT-1) and osteopontin (OPN), and stem cell-associated genes survivin, epidermal growth factor receptor (EGFR), human telomerase reverse transcriptase (hTERT), Nanog and octamer binding transcription factor 4 (OCT4) using quantitative real-time polymerase chain reaction (qRT-PCR). Our data revealed higher mRNA expression levels of hypoxia-induced and stem cell-associated genes in tumour tissue than levels in the tumour adjacent tissues in patients with glioblastoma multiforme. A strong positive correlation between the mRNA expression levels of HIF-2 alpha, CA9, VEGF, GLUT-1 and OPN suggests a specific hypoxia-associated profile of mRNA expression in glioblastoma multiforme. Additionally, the results indicate the role of stem-cell-related genes in tumour hypoxia. Kaplan-Maier analysis revealed that high mRNA expression levels of hypoxia-induced markers showed a trend towards shorter overall survival in glioblastoma patients (P=0.061). Our data suggest that mRNA expression levels of hypoxia-induced genes are important tumour markers in patients with glioblastoma multiforme.Wilhelm Sander Stiftung [2013.090.1
Osteopontin and splice variant expression level in human malignant glioma: Radiobiologic effects and prognosis after radiotherapy
No full textBackground and purpose: We investigated the role of the hypoxia-associated secreted glycoprotein osteopontin (OPN) in the response of malignant glioma to radiotherapy by characterizing OPN and its splice variants in vitro and in patient material. Material and methods: The effect of siRNA knockdown of OPN splice variants on cellular and radiobiologic behavior was analyzed in U251MG cells using OpnS siRNA (inhibition of all OPN splice variants) and OpnAC siRNA (knockdown only of OPNa and OPNc). OPN and splice variant mRNA levels were quantified in archival material of 41 glioblastoma tumor samples. Plasma OPN was prospectively measured in 33 malignant glioma patients. Results: Inhibition of OPNa and OPNc (OpnAC) reduced clonogenic survival in U251MG cells but did not affect proliferation, migration or apoptosis. Knockdown of all OPN splice variants (OpnS) resulted in an even stronger inhibition of clonogenic survival, while cell proliferation and migration were reduced and rate of apoptosis was increased. Additional irradiation had additive effects with both siRNAs. Plasma OPN increased continuously in malignant glioma patients and was associated with poor survival. Conclusions: OPNb is partially able to compensate the effects of OPNa and OPNc knockdown in U251MG cells. High OPN plasma levels at the end of radiotherapy are associated with poor survival. (C) 2013 Elsevier Ireland Ltd. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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