1,721,009 research outputs found
Identifying novel therapeutic strategies for brain metastatic and mucosal melanoma
Get PDFMelanoma encompasses a number of malignancies all originating from cells of melanocytic origin. Generally speaking, melanoma has a promising prognosis with a five-year survival rate of 91.3%, however two subtypes in particular – melanoma brain metastasis (MBM) and mucosal melanoma (MM) – have a high mortality and limited therapeutic options. Cancerous cells frequently have altered metabolic pathways in order to sustain their rapid growth. Cutaneous melanoma has previously been shown to be both arginine dependent and arginine auxotrophic due to silencing of the enzyme argininosuccinate synthase 1 (ASS1), which catalyses de novo arginine synthesis. As a result, arginine deprivation has demonstrated efficacy in the treatment of melanoma, however to date MBM have been excluded from trials. I hypothesised that MBM will be particularly sensitive to arginine deprivation due to it’s observed increased dependency on arginine metabolism and oxidative phosphorylation compared
to primary cutaneous melanoma. Results show ASS1 is repressed in both MBM and extracranial melanoma metastasis (EMM), but that this is reversible in some cell lines upon arginine
starvation with ADI-PEG20. Regardless of ASS1 upregulation, MBM and EMM were found to
be sensitive to ADI-PEG20 via mitochondrial fragmentation followed by apoptotic cell death.
The induction of autophagy and epigenetic remodeling of glutamate related pathways constitute two potential resistance mechanisms which were identified. MM is a rare and understudied cancer with very little known about it’s pathogenesis. Investigation of the mutational profile and immunology of disease was hypothesised to identify potentially novel therapeutic targets. Results show oncogeneic pathways similar to those activated in cutaneous melanoma are mutated in MM, however novel pathways unique to MM
were also identified. All significantly mutated pathways were associated with MAPK signalling,
PI3K/AKT signalling, and the Warburg effect, suggesting these to be potentially important
therapeutic targets. Tumours were heavily infiltrated with immune cells in a site specific manner, with gastric and urogenetial tumours displaying infiltration of an anti-tumour immune population, and nasal tumours displaying mixed pro- and anti-tumour infiltration alongside epithelial-to-mesenchymal transition (EMT). Taken together, this study identifies suitable therapies and therapeutic targets for hard-to-treat MBM and MM.Open Acces
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
Metabolic profiling of ASS1 negative and ASS1 positive glioblastoma subtypes to identify novel targets for therapy
Get PDFGlioblastoma multiforme (GBM) are the most common and most malignant brain tumours. Despite treatment advances, average survival remains unacceptably low with 15-months, hence novel therapies are desperately needed. Cellular metabolism plays a central role in cancers. Sensitivity towards arginine-deprivation via pegylated arginine deaminase (ADI-PEG20) therapy has been identified in GBM, arresting proliferation in methylated arginino-succinate-synthetase-1 (ASS1M) and not unmethylated ASS1 (ASS1U) GBM cells. Advances of biochemical techniques and analysis have facilitated therapeutic target identification as well as biomarker discovery.
Complimentary gas-chromatography coupled with mass spectrometry and 1-hydrogen nuclear-magnetic-resonance spectroscopy of in vitro GBM cells identified distinct metabolic profiles in ASS1 subtypes. Intracellular and extracellular analysis of GBM cells exposed to ADI-PEG20 treatment elucidated metabolic perturbations in the arginine, creatine, glycolytic, uridine, citric acid, thymine and glutamine pathways, induced by arginine deprivation.
Transcriptional analysis of perturbed pathways elucidated differentially altered enzymatic expression in ASS1 GBM subtypes upon ADI-PEG20 treatment. Significantly modulated enzymes included transcriptional down-regulation of thymidylate synthase (TYMS) in ASS1M GBM cells, whereas ASS1U remained unaltered. Significantly altered enzymatic mRNA expression also identified modulation of glutamic pyruvate transaminase 2 (GPT2) in ASS1M cells, as well as thymidine kinase 2 (TK2) and alanine-glyoxylate aminotransferase 2 (AGXT2) in ASS1U GBM.
Targeting the de novo thymine and creatine metabolic pathway, demonstrated that phytic acid (IP6) arrests proliferation in GBM cells, whereas creatine supplementation boosted proliferation. IP6 arrested proliferation in a time- and dose-dependent manner, irrespective of ASS1 status. Combining IP6 and ADI-PEG20, showed arrested proliferation was enhanced, compared to either treatment alone in ASS1M GBM cells.Open Acces
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
Development of systems to conditionally silence genes in the immune system of the mouse
No full textEThOS - Electronic Theses Online ServiceGBUnited Kingdo
Engineering pseudovirions for large-scale targeted gene transfer and recombinant adeno-associated virus production
Get PDFGene transfer is a technology central to the development of gene therapy and expression of proteins and biological products necessary for designing and producing drug compounds or creating new research methodologies. Consequently, the field has experienced a large bottleneck in economic and time costs when viral vectors are involved. Over the past decade, recombinant mammalian viral vectors have been exploited for these purposes; however, the limitations in their native biology and production methods warrant new vector systems to be investigated and developed. In this thesis, we reinvestigate the humble bacteriophage, a prokaryotic virus, as a potential tool to circumvent the cost limitation of eukaryotic viruses. By combining their genome with that of Adeno-associated virus (AAV), a well-characterised mammalian virus, and developing a novel method of expressing these hybird vectors, we were able to overcome many limitations that these viruses have as separate entities. The proposed vector, termed Phagemid Adeno-associated Virion (PAAV), is as efficacious as traditional vectors, while economically costing a fraction of what is demanded by current practice in the field.
The PAAV, was constructed by inserting a recombinant AAV genome into a phagemid expression vector that carries no phage structural genes. The particles are packaged using a custom-designed mammalian-targeted helper virus, resulting in vectors that can be easily produced at a minimum of 2-fold higher yield than the current gold-standard phage vector. We demonstrated through transmission electron microscopy and transducing unit assays that PAAV vectors generated by our method is less than half the size of traditional full-length phage vectors, and through vesicular staining we are able to determine that the PAAV is internalised at almost 2-fold higher than the efficiencies observed in the gold-standard phage vector. We further assessed qualitative and quantitative gene expression efficacies by the PAAV bearing GFP or Luciferase transgenes in various tumour cells, which show a dramatic increase in gene expression by up to over 10-fold of the gold-standard. To demonstrate that the PAAV and its derived vectors can be used as an alternative to DNA transfection, a method central to mammalian virus production, we designed and validated two proof-of-concept methods that are able to produce rAAV using PAAV vectors.
Phages are harmless viruses with a safety profile founded by their historic use as antibiotic agents. The PAAV vector system utilizes the economic advantages of phage vectors and combines them with the efficacy of mammalian viral transgenes, offering an efficacious alternative vector that is able to transduce mammalian tumour cells. Furthermore, the PAAV system has the potential to replace conventional transfection, thereby addressing a significant bottleneck in translational research in the field. Taken together, the PAAV offers a novel and advantageous alternative platform to conventional viruses for use in therapeutic and industrial applications.Open Acces
The regulatory role of the NCoR/HDAC3 complex in Alzheimer's disease pathology
No full textIn the brain of Alzheimer’s disease (AD) patients, accumulation of amyloid-β and tau is accompanied by synaptic and neuronal loss and chronic inflammation. Amyloid-β is generated from the processing of the amyloid precursor protein (APP), through sequential cleavage by the β-APP-cleaving enzyme (BACE1) and the γ-secretase. The BACE1 promoter contains consensus binding sites for transcription factors, including the Peroxisome Proliferator-activated receptor-γ (PPAR- γ). PPAR- γ is a nuclear receptor, which upon ligand activation can regulate the transcription of target genes. Therefore, manipulation of PPAR-γ activity may present a potential avenue for targeting AD pathology. Nuclear receptor co-repressor 1 (NCoR) is a co-repressor of PPAR-γ, amongst other transcription factors, and exerts its repressive function by working with histone deacetylase 3 (HDAC3). We hypothesised that NCoR drives production of amyloid-β in AD through PPAR-γ modulation and our aim was to investigate the mechanisms whereby NCoR affects amyloid-β generation and degradation in the N2a neuroblastoma cell line. In addition, we assessed whether HDAC3 inhibition resulted in the opposite effects, and also affected synaptic and inflammatory markers in an ex vivo AD model. We have shown that NCoR is enriched in neurons and certain glial cells, that its expression is increased in the hippocampus of AD patients compared with healthy controls, and that NCoR increases with age. In addition, NCoR over-expression in N2a cells resulted in increased BACE1 expression, while it led to a reduction in the levels of APP and amyloid-β. Conversely, inhibition of HDAC3, using a specific inhibitor, resulted in elevations of APP and amyloid-β levels. Furthermore, HDAC3 inhibition in organotypic brain cultures of 5xFAD mice increased APP expression, lowered glial activation and rescued spine density, without altering amyloid-β levels. These data suggest that NCoR and HDAC3 play multi-faceted roles in the modulation of AD pathology, most prominently on the expression of APP, and that targeting the NCoR/HDAC3 complex could be a promising therapeutic strategy for AD.Open Acces
Augmented visualisation of tumour boundaries and functioning brain during neurosurgery
No full textIntroduction. Surgery for brain tumours represents a major and multidisciplinary challenge. An extensive body of literature suggests a non-linear correlation between the extent of resection and survival. However, resection is often limited by the difficulty of exactly identifying the degree of brain invasion and the presence of functionally active areas.
Hypothesis. The project examines the hypothesis of advancing the current technological setup in neurosurgery, specifically attempting to visually improve the identification of tumour margins and eloquent brain activation.
Aims. To investigate:
• to evaluate the role and optimization of IntraOperative UltraSound (IOUS) in brain
tumour resection;
• to assess how Hyperspectral Imaging (HSI) can enhance the visualization of tumour margins
and detect haemodynamic changes in real-time.
Methods. The present thesis expands on the candidate’s experience with IOUS, reporting a published analysis of the advantages. The results of performance and technical limitations are also discussed. Regarding the HSI application, the thesis details the results from a pilot study applying these technologies intra-operatively. Hyperspectral data (hypercube images) were processed using various computational techniques, and brain haemodynamics were analyzed through an adapted Beer-Lambert model. Results. The IOUS series included 391 cases, and the data showed a resection and survival advantage in glioblastomas. Cases operated using IOUS showed an improved resection and a possible survival advantage. Regarding MSI/HSI, 47 patients have been recruited. The following findings were recorded: all the algorithms for intra-patient classifications showed excellent performance on all metrics; the inter-patent classification methods showed a better performance with meningiomas but more heterogeneous results with gliomas; the perfusion maps showed statistically significant changes in brain perfusion, although
the clinical significance of these findings is unclear.
Conclusions. The results reported in the present project are promising for the further technological
development of both iOUS and HSI.Open Acces
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