1,720,971 research outputs found
Extracellular matrix-degrading enzymes and control of fibroblast growth factor-2 (FGF-2) signaling in pediatric glioma cell lines
Full text linkThe main purpose of my research project was to investigate the role of two extracellular matrix-degrading enzymes, heparanase (HPSE) and membrane-type 1 matrix metalloproteinase (MT1-MMP), in pediatric gliomas. I spent the first two years of my PhD program in Dott. Maurizio Onisto’s laboratory (University of Padua). Then I continued my work at New York University School of Medicine, under the supervision of Prof. Paolo Mignatti, whose experimental work focuses on the molecular mechanisms of proteolysis-independent signaling by MT1-MMP and its physiological inhibitor, tissue inhibitor of metalloproteinase-2 (TIMP-2).
Gliomas, the most common primary brain tumors, comprise a heterogeneous group of neoplasms that originate from glial cells. Despite recent advances in the management of these tumors, children affected by gliomas, particularly the more aggressive forms, have a poor prognosis. Gliomas can diffusely penetrate throughout the brain, even though they remain localized in this organ. One of the most important events during glioma cell invasion is extracellular matrix (ECM) degradation, a complex mechanism that involves both glycosidic and proteolytic enzymes. HPSE is an endo-β-D-glucuronidase secreted in the ECM, where it cleaves the heparan sulfate side chains of both soluble and membrane-bound proteoglycans. MT1-MMP, a cell membrane-bound proteinase with an extracellular catalytic domain and a short cytoplasmic tail, has been implicated in the proteolytic degradation of extracellular and transmembrane proteins. High levels of HPSE and MT1-MMP are present in a variety of aggressive malignancies, a finding that highlights their important role in cancer invasion and metastasis.
In this study we characterized pediatric glioma cell lines derived from different types of gliomas: two glioblastoma multiforme, one anaplastic astrocytoma, one diffuse astrocytoma and one pilocytic astrocytoma. In addition, we used a human breast adenocarcinoma cell line to examine the role of MT1-MMP, because these cells do not express this proteinase and thus represent an ideal model for the regulation of its expression.
The data reported here show that MT1-MMP controls activation of intracellular signaling by fibroblast growth factor-2 (FGF-2) and FGF-2 binding to the breast adenocarcinoma cells. We found no clear correlation between HPSE, MT1-MMP or FGF-2 expression and the aggressiveness of the pediatric astrocytoma cells. Gene silencing of HPSE in a pediatric glioblastoma cell line does not affect vascular endothelial growth factor (VEGF) expression or cell proliferation, but upregulates matrix metalloproteinase-2 (MMP-2) and MT1-MMP expression. Moreover, ERK1/2 activation by FGF-2 does not correlate with MT1-MMP expression and is modified by an MMP inhibitor in these pediatric glioma cells. Finally, TIMP-2 controls ERK1/2 activation in all glioma cells.
Taken together, the results show that MT1-MMP does not have the same effects in breast carcinoma and pediatric glioma cells, indicating a different and more complex control mechanism of intracellular signaling. This initial characterization of these unique pediatric astrocytoma cell lines provides new insights into the knowledge of this poorly studied group of tumors.L’obiettivo principale del mio progetto di ricerca è stato analizzare il ruolo di due enzimi che degradano la matrice extracellulare, l’“heparanase” (HPSE) e la “membrane-type 1 matrix metalloproteinase” (MT1-MMP), nei gliomi pediatrici. Ho trascorso i primi due anni di Dottorato nel laboratorio del Dott. Maurizio Onisto (Università di Padova). Ho poi continuato il mio lavoro presso la New York University School of Medicine, sotto la supervisione del Prof. Paolo Mignatti, il cui lavoro sperimentale è focalizzato sull’approfondimento dei meccanismi molecolari alla base dell’attivazione del segnale intracellulare da parte di MT1-MMP e del suo inibitore fisiologico, il “tissue inhibitor of metalloproteinases-2” (TIMP-2).
I gliomi, i più comuni tumori cerebrali primari, comprendono un gruppo eterogeneo di neoplasie che originano dalle cellule gliali. Nonostante i recenti progressi raggiunti nel trattamento e nel controllo di tali tumori, la prognosi dei bambini affetti da glioma, ed in particolare dalle sue forme più aggressive, rimane tuttora infausta. Pur essendo confinati nell’organo nel quale originano, i gliomi possono invadere tutte le aree del cervello. Uno degli eventi più importanti che caratterizzano l’invasività dei gliomi è costituito dalla degradazione della matrice extracellulare, un complesso meccanismo che coinvolge enzimi sia glicosidici sia proteolitici. HPSE è una endo-β-D-glucuronidasi secreta nella matrice extracellulare, nella quale taglia le catene di eparan solfato dei proteoglicani solubili e legati alla membrana. MT1-MMP, una proteasi legata alla membrana e composta da un dominio catalitico extracellulare e da una piccola coda citoplasmatica, è coinvolta nella degradazione proteolitica di proteine extracellulari e di membrana. Elevati livelli di HPSE e MT1-MMP sono stati riscontrati in numerosi tipi di tumore e tale evidenza sottolinea il ruolo chiave che essi svolgono nell’invasività tumorale e nella formazione di metastasi.
In questo studio sono state caratterizzate cinque linee cellulari di glioma pediatrico derivanti da diversi tipi di glioma: due glioblastomi multiformi, un astrocitoma anaplastico, un astrocitoma diffuso ed un astrocitoma pilocitico. Con lo scopo iniziale di esaminare il ruolo di MT1-MMP nell’attivazione del segnale indotto dall’FGF-2, è stata inoltre utilizzata una linea cellulare di carcinoma mammario, la quale non esprime MT1-MMP e perciò rappresenta un modello ideale per studiare la regolazione della sua espressione.
I dati riportati mostrano che, nelle cellule di carcinoma mammario, MT1-MMP regola l’attivazione del segnale intracellulare da parte del “fibroblast growth factor-2” (FGF-2) e controlla il legame di questo fattore di crescita alla superficie delle cellule.
Nelle cellule di astrocitoma pediatrico non è stata identificata alcuna chiara correlazione tra espressione di HPSE, MT1-MMP o FGF-2 ed aggressività tumorale. I risultati inoltre dimostrano che il silenziamento genico di HPSE in una linea cellulare di glioblastoma pediatrico non influenza l’espressione del “vascular endothelial growth factor” (VEGF) o la proliferazione cellulare, ma determina la sovraespressione della “matrix metalloproteinase-2” (MMP-2) e di MT1-MMP. Inoltre, nelle cellule di glioma, l’attivazione di ERK1/2 da parte di FGF-2 non correla con l’espressione di MT1-MMP e risulta modificata dal trattamento con un inibitore di MMP. Infine, in tutte le cellule di glioma, anche TIMP-2 regola l’attivazione del segnale intracellulare.
In conclusione, i risultati ottenuti mostrano che MT1-MMP non ha gli effetti nelle cellule di carcinoma mammario e di glioma pediatrico, indicando l’esistenza di un differente e più complesso meccanismo di controllo del segnale intracellulare. La caratterizzazione delle linee cellulari di astrocitoma pediatrico presentata in questa tesi offre una più completa conoscenza di questo gruppo di tumori ancora poco studiati
A Genome-Wide CRISPR-Cas9 Loss-of-Function Screening to Identify Host Restriction Factors Modulating Oncolytic Virotherapy
No full textOncolytic virotherapy represents an efficient immunotherapeutic approach for cancer treatment. Oncolytic viruses (OVs) promote antitumor responses through tumor-selective cell lysis and immune system activation. However, some tumor cell lines and primary tumors display resistance to therapy. Here we describe a protocol to identify novel host factors responsible for tumor resistance to oncolysis using an unbiased genome-wide CRISPR-Cas9 loss-of-function screening. Cas9-expressing tumor cells are transduced with a library of pooled single-guide RNA (sgRNA)-expressing lentiviruses that target all human genes to obtain a cell population where each cell is knocked out for a single gene. Upon OV infection, resistant cells survive, while sensitive cells die. The relative abundance of each genome-integrated sgRNA is measured by next-generation sequencing (NGS) in resistant and control cells. This protocol is amenable to uncover host factors involved in the resistance to different OVs in multiple tumor models
The story of SPATA2 (Spermatogenesis-associated Protein 2): from Sertoli cells to pancreatic beta-cells.
Full text linkIn an attempt to isolate new spermatogenesis-associated genes, pd1 was initially identified and cloned as a novel human cDNA sequence from testis cDNA library. The novel gene was submitted to GenBank under accession n degrees U28164 in 1996. PD1 expression was demonstrated at the Sertoli cell level with a production which appeared to be under the influence of neighbouring spermatogenic cells. The rat orthologue of human pd1 was further cloned and, according to the Gene Nomenclature Committee, was renamed spata2 (spermatogenesis-associated protein 2) gene on the basis of its FSH-dependent up-regulation and developmental expression. The analysis of the human and rat cDNA sequences disclosed an open reading frame for a protein of 520 and 511 amino acids respectively, with an overall identity of 85%. Subsequently, a zebrafish orthologue of the human spata2 gene was identified. The consensus open reading frame (1650 bp) encodes a polypeptide of 550 amino acids, which shares 37% identity with the human spata2. By means of whole-mount in situ hybridisation it has been shown that spata2 transcripts are maternally derived and become strongly localised in the central nervous system at early developmental stages. At the same time, RT-PCR analysis demonstrated that several adult zebrafish tissues expressed high level of spata2 mRNA providing evidence that this gene may have a broader function than previously described. More recently, novel findings have highlighted a potential role of spata2 during pancreatic development and beta-cell proliferation. In this review we will discuss spata2 gene expression and regulation as well as focus on novel evidence, which suggests a role for this protein in pancreatic beta-cell function
Antidepressant hyperforin up-regulates VEGF in CNS tumour cells.
No full textVascular endothelial growth factor (VEGF) is a key player in neo-angiogenesis; it sustains the progression of solid neoplasias, brain tumours included. It has recently been demonstrated that the use of antidepressants correlates with increasing VEGF levels in the central nervous system (CNS). In order to elucidate whether the most used natural antidepressant [St. John's wort (SJW) extract] modulates VEGF expression, possible relationship between≤μM hyperforin (Hyp, the bioactive component in SJW) and VEGF in CNS tumours has been now examined in medulloblastoma and glioblastoma cells. Real-time PCR and ELISA revealed that under Hyp VEGF expression increased more than three fold in DAOY medulloblastoma cells; while, U87 glioblastoma cells - constitutively expressing high VEGF levels - showed no significant differences. Moreover, Hyp induced endothelial pro-angiogenic behaviour in a multi-parametric Matrigel colonisation assay, and down-modulation of pro-MMP-2 and pro-MMP-9 activities as measured by gelatin zymography. Should these results be confirmed in vivo for this and other types of CNS tumour, the antidepressant use of SJW extracts must be carefully re-considered, in particular for brain tumour patients
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
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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