1,721,036 research outputs found
Targeting Hedgehog pathway in medulloblastoma: identification of SALL4A as a new activator and isoflavone c22 as multitarget inhibitor
Full text linkHedgehog (Hh) pathway is essential for embryonal development and tissues homeostasis; its alteration causes several human cancers, including medulloblastoma (MB), the most common brain malignancy in childhood. Because of its crucial role in tumorigenesis, the regulation of the Hh pathway and the identification of new Hh modulators emerged as a field of great interest in tumor biology.
My Ph. D. project was focused on two main goals:
Aim 1 | Identification of new molecular mechanisms involved in Hh signalling pathway regulation and MB tumorigenesis. To address this aim, we focused on the identification of new interactors of the known Hh negative regulator and tumor suppressor RENKCTD11. Through mass spectrometry analysis, we identified the transcription factor SALL4A. SALL4A plays a key role in maintaining pluripotency and self-renewal of embryonic stem cells, regulating different signalling pathway. SALL4A expression is inhibited in the post-natal period in many adult tissues, but it is reactivated in different tumors and is often related to worse prognosis and lower survival rate. Our data demonstrate that SALL4A is a substrate of RENKCTD11, that induces its poly-ubiquitylation and its consequent proteasome-mediated degradation. In order to investigate its biological role in Hh signalling, we demonstrated that SALL4A enhances GLI1 activity working in complex with HDAC1, a well known Hh activator. Of note, we observed that the proliferation ability of human MB cell lines increases in presence of SALL4A, whereas their migration rate is reduced after its genetic depletion; in vivo, SALL4A genetic depletion leads to a reduction of Hh-dependent tumor growth. Our findings identify SALL4A as a previously unknown regulator of Hh pathway able to promote, in complex with HDAC1, GLI1 activity and to contribute to Hh-dependent tumorigenesis. Hence, SALL4A stands as a new molecular target involved in the onset and progression of Hh-dependent tumors and represents an interesting focus in cancer research.
Aim 2 | Pharmacological targeting of Hedgehog pathway. Given the primary role of Hh signalling in tumorigenesis and in the maintenance of cancer stem cell niches, this pathway is now considered an attractive therapeutic target in cancer. In recent years, many efforts have focused on the development of drugs that can block the activating effect of SMO receptor. However, several studies underlined some limitations of the inhibitors identified so far, linked in particular to the poor selectivity, the onset of drug resistance events and the activation of GLI1 mediated by other oncogenic pathways. These evidences raise the need to identify new and more effective Hh inhibitors able to overcome drug resistance and to counteract tumor growth. To this end, my research activity was aimed at identifying, characterizing and optimizing new molecules able to block the oncogenic potential of Hh. In particular, by combining the most profitable pharmacophores for targeting SMO and GLI1 by synthetic isoflavones, we designed and synthesized the isoflavone 22, a small molecule that acts as a multitarget Hh inhibitor blocking both SMO and GLI1 activity at the same time. Compound 22 is able to inhibit Hh-dependent tumor growth in human and murine MB cells at sub-micromolar concentration, as a consequence of the reduction in GLI1 expression levels. Isoflavone 22 remarkably shows a strong anti-tumor effect also in vivo by suppressing cell proliferation and promoting apoptosis. Molecular modeling further corroborated the multitarget mechanism of action of compound 22, showing that the drug is able to fit the ligand binding site in both SMO and GLI1. Overall, these results reveal a valuable form of targeted therapy to increase the efficacy and to decrease the toxicity of individual anticancer agents; our findings discover the first multitarget Hh inhibitor that impinges Hh-dependent tumor growth and stands as new potential weapons against Hh-driven tumors
Swelling Rocks Investigation on Hydro Tunnels – A Comprehensive Characterization based on Laboratory Tests and Constitutive Models
No full textSwelling of rocks is a common phenomenon in the Andean Region, due to the presence of volcano-sedimentary units containing clays, typically from the smectite group as part of the rock matrix. Hence, a comprehensive rock mass characterization has to be made in order to evaluate the risk of underground works located in this kind of geological environment. For hydro tunnels in South America, a set of swelling pressure tests of different type (on intact rock discs, ground rock powder, cyclic loading and triaxial tests) were executed for swelling potential evaluation. The results show that obtained values are highly dependent on test procedures, suggesting that swelling pressure test has to be considered as an index, instead of a definitive value of pressure (especially when using ground rock powder). A result comparison and discussion is included in this paper and recommendations for engineering design are provided based on numerical modelling
The post-genomic era: workshop on chromatin immunoprecipitation-related techniques
No full text[No abstract available
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
HSP-CBF is an NF-Y-dependent coactivator of the heat shock promoters CCAAT boxes
Full text linkThe cellular response to toxic stimuli is elicited through the expression of heat shock proteins, a transcriptional process that relies upon conserved DNA elements in the promoters: the Heat Shock Elements, activated by the heat shock factors, and the CCAAT boxes. The identity of the CCAAT activator(s) is unclear because two distinct entities, NF-Y and HSP-CBF, have been implicated in the HSP70 system, The former is a conserved ubiquitous trimer containing histone-like subunits, the latter a 110-kDa protein with an acidic N-terminal, We analyzed two CCAAT-containing promoters, HSP70 and HSP40, with recombinant NF-Y and HSP-CBF using electrophoretic mobility shift assay, protein-protein interactions, transfections and chromatin immunoprecipitation assays (ChIP) assays. Both recognize a common DNA-binding protein in nuclear extracts, identified in vitro and in vivo as NF-Y, Both CCAAT boxes show high affinity for recombinant NF-Y but not for HSP-CBF, However, HSP-CBF does activate HSP70 and HSP40 transcription under basal and heat shocked conditions; for doing so, it requires an intact NF-Y trimer as judged by cotransfections with a diagnostic NF-YA dominant negative vector. HSP-CBF interacts in solution and on DNA with the NF-Y trimer through an evolutionary conserved region. In yeast two-hybrid assays HSP-CBF interacts with NF-YB, These data implicate HSP-CBF as a non-DNA binding coactivator of heat shock genes that act on a DNA-bound NF-Y
Variations on the Author
Full text link“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
Full text linkWe 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
Full text linkWe 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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