Orientador: Ana Elizabete Silva / Banca: Patrícia Matos Biselli Chicote / Banca: Marília de Freitas Calmon Saiki / Resumo: Introdução: A inflamação crônica desencadeada pela bactéria Helicobacter pylori (H. pylori), a qual é considerada o principal fator ambiental relacionado ao câncer gástrico, está associada ao desenvolvimento e progressão de lesões gástricas pré-cancerosas, desencadeando diversas modificações histológicas e moleculares que promovem a transformação maligna do estômago. Para isso, conta com fatores de virulência que promovem alterações superficiais e em vias de sinalização das células epiteliais gástricas. Consequentemente pode levar a alterações no padrão de expressão de genes supressores tumorais e da atividade de enzimas DNA metil transferases (DNMTs), responsáveis pela metilação do DNA e silenciamento gênico. Objetivos: O presente estudo avaliou se a infecção pela bactéria H. pylori, bem como sua erradicação, altera a expressão do RNAm dos genes supressores SOCS1, RPRM, RUNX3 e dos genes de DNMTs (DNMT1, DNMT3A e DNMT3B) em pacientes com gastrite crônica infectados (Hp+) em comparação com indivíduos com gastrite crônica sem infecção (Hp-). Além disso, investigou a ocorrência de correlação negativa entre a expressão do RNAm dos genes supressores tumorais com a dos genes das DNMTs, assim como a associação dos níveis de expressão gênica em relação aos fatores de risco idade, sexo, tabagismo, etilismo e genótipo bacteriano cagA. Material e Métodos: A quantificação relativa (RQ) do RNAm foi realizada por PCR (polymerase chain reaction) quantitativa em tempo real (qPCR) utilizando ensaios TaqMan® em 9 pacientes com gastrite crônica Hp- e 19 Hp+, sendo estes também avaliados três meses depois da terapia de erradicação bacteriana. O diagnóstico molecular e genotipagem do fator de virulência cagA foram realizados por PCR convencional. Resultados: Os resultados mostraram que a infecção pela H. pylori e sua erradicação... / Abstract: Introduction: Chronic inflammation caused by Helicobacter pylori (H. pylori), which is considered the main environmental factor related to gastric cancer, is associated with the development and progression of precancerous gastric lesions, triggering several histological and molecular changes that promote stomach malignant transformation. For this, it has virulence factors promoting superficial and signaling pathways of gastric epithelial cells changes. Consequently, it can lead to alterations in the expression of tumor suppressor genes and DNA enzyme activity methyl transferases (DNMTs), responsible for DNA methylation and gene silencing. Objectives: This study evaluated whether the infection by the bacterium H. pylori and its eradication change the mRNA expression of suppressor genes SOCS1, RPRM, RUNX3 and DNMTs (DNMT1, DNMT3A and DNMT3B) genes in patients with chronic gastritis infected (Hp+) compared to individuals with chronic gastritis without infection (Hp-). In addition, we investigated the occurrence of negative correlation between mRNA expression of tumor suppressor genes with the ones of DNMTs, as well as the association of gene expression levels in relation to the risk factors age, sex, smoking, drinking and bacterial genotype cagA. Methods: The relative quantification (RQ) mRNA was performed by PCR (polymerase chain reaction) quantitative real-time (qPCR) using TaqMan® assays in 9 patients with chronic gastritis Hp- and 19 Hp+, which are also evaluated three months after bacterial eradication therapy. The molecular diagnostics and genotyping of the virulence factors CagA were performed by standard PCR. Results: The results showed that the infection by H. pylori and eradication did not significantly alter the gene expression of SOCS1, RPRM, RUNX3 and DNMTs, which presented, in general, reduced expression (RQ <1.0); on the other hand, higher expression of SOCS1 and ... / Mestre

Abstract not available

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Pathology / Master / Master of Philosophy

Thesis (Ph.D.)--University of Alberta, 2009. / A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy, Department of Biochemistry. Title from pdf file main screen (viewed on August 11, 2009). Includes bibliographical references.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 187-198). Also available in print.

Thesis (Ph. D.)--University of Oregon, 2006. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 68-71). Also available for download via the World Wide Web; free to University of Oregon users.

Made available in DSpace on 2015-04-09T12:28:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-02-21Bitstream added on 2015-04-09T12:47:34Z : No. of bitstreams: 1 000811842.pdf: 747851 bytes, checksum: 12d5b852f7d8f1956044b6f1de50c444 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / As Síndromes Mielodisplásicas (SMD) definem um grupo de doenças clonais das células hematopoéticas caracterizadas por citopenias, displasia em uma ou mais linhagens celulares mielóides, hematopoese ineficaz e aumento do risco de evolução para leucemia mielóide aguda. A frequência de doentes que progridem para o câncer varia com o subtipo de SMD, de acordo com a classificação da Organização Mundial da Saúde. As SMD são consideradas doenças pré-malignas e, ao contrário de outras doenças hematológicas, como as leucemias, estão geralmente associadas a anomalias cromossômicas desequilibradas. Estas consistem principalmente em deleções, translocações e alterações numéricas. Também são frequentemente observadas perdas de material genético, com consequente inativação de genes supressores tumorais. Estes genes controlam mecanismos biológicos vitais, como reparo do DNA, crescimento e morte celular programada. Um exemplo é o supressor de tumor RASSF1A (Ras-association domain family 1, isoform A), mapeado em 3p21.3. A falta de expressão deste gene e taxas elevadas de mutações, especialmente envolvendo os exons 3, 4 e 5, foram descritas em diversos tipos de cancêr, mas nunca foram investigadas em SMD. Neste contexto, este projeto teve como proposta investigar a presença de alterações cromossômicas e de mutações nos exons 3, 4 e 5 do gene RASSF1A em indivíduos com SMD ao diagnóstico e em controles normais. Foram estudados 50 casos dos quais foram realizadas culturas de curta duração (24 horas) de células de medula óssea sem estimulação mitogênica e sequenciamento direto dos exons de interesse. Quatro casos (8%) apresentaram alterações cromossômicas, caracterizadas como hipodiploidia em dois casos, monossomia do cromossomo 7 em um e um cariótipo complexo envolvendo os cromossomos 3, 5 e 11 em outro. A análise molecular dos exons 3, 4 e 5 dos 50 casos revelou dois (4%) casos com o polimorfismo ... / The myelodysplastic syndromes (MDS) are characterized by cytopenias, dysplasia in one or more myeloid cell lines, ineffective hematopoiesis and an increased risk of acute myeloid leukemia (AML) transformation. The rate of patients who progress to AML varies by subtype of disease, according to the World Health Organization classification. The MDS are considered premalignant diseases and unlike of other hematological diseases, such as leukemia, are mostly associated with unbalanced chromosomal abnormalities, as deletions, translocations and numerical changes, beyond loss of genetic material with consequent tumor suppressor genes inactivation, which can control biological mechanisms such as DNA repair, growth and programmed cell death. An example is the tumor suppressor RASSF1A (Ras-association domain family 1, isoform A) mapped in 3p21.3. The high mutation rates and no expression of this gene, mainly exons 3, 4 and 5, have been described in several types of cancer but have never been investigated in MDS. Thereby chromosomal changes and mutations in exons 3, 4 and 5 from RASSF1A of the bone marrow cells from 50 cases the diagnosis of MDS were investigated. The assays were accomplished for 24 hours applying bone marrow cells without mitogenic stimulation and the exons were straight sequenced, where four samples (8%) had chromosomal abnormalities, characterized for hypodyploidy (two cases), monosomy 7 and complex karyotype involving chromosomes 3, 5 and 11. Molecular analysis revealed two (4%) other cases with Ala133Ser polymorphism (A133S) in exon 3. The cytogenetic changes observed are related to the MDS developed, while the polymorphism has been proposed to be involved in some types of cancers predisposition. The results can support other studies which are searching for genetic factors involved in the pathogenesis of MDS

The Mdm2 and Mdm4 oncoproteins are key negative regulators of the p53 tumor suppressor. However, their physiological contributions to the regulation of p53 stability and activity remain highly controversial. Here, we combined a p53 knock-in allele, in which p53 is silenced by a transcriptional stop element flanked by loxP sites, with the Mdm2- and Mdm4-null alleles. This approach allows Cre-mediated conditional p53 expression in tissues in vivo and cells in vitro lacking Mdm2, Mdm4, or both. Using this strategy, we show that Mdm2 and Mdm4 are essential in a nonredundant manner for preventing p53 activity in the same cell type (Mouse Embryonic Fibroblasts (MEFs), neuronal progenitor cells and postmitotic neurons) and irrespective of the proliferation/differentiation status of the cells. Although Mdm2 prevents accumulation of the p53 protein, Mdm4 contributes to the overall inhibition of p53 activity independent of Mdm2. We propose a model in which Mdm2 is critical for the regulation of p53 levels and Mdm4 is critical for the fine-tuning of p53 transcriptional activity, both proteins acting synergistically to keep p53 in check. Finally, we show that neither Mdm2 nor Mdm4 regulate cell cycle progression independently of its ability to modulate p53 function. / Doctorat en sciences, Spécialisation biologie moléculaire / info:eu-repo/semantics/nonPublished

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