• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 6
  • 5
  • 1
  • Tagged with
  • 15
  • 15
  • 15
  • 15
  • 8
  • 6
  • 6
  • 6
  • 6
  • 3
  • 3
  • 3
  • 3
  • 2
  • 2
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

ARHGAP4 is a spatially regulated RhoGAP that inhibits NIH/3T3 cell migration and dentate granule cell axon outgrowth

Vogt, Daniel. January 2007 (has links)
Thesis (Ph. D.)--Case Western Reserve University, 2007. / [School of Medicine] Department of Neurosciences. Includes bibliographical references. Available online via OhioLINK's ETD Center.
2

Cell signaling by Rho and Miro GTPases : studies of Rho GTPases in cytoskeletal reorganizations and of Miro GTPases in mitochondrial dynamics /

Fransson, Åsa, January 2008 (has links)
Diss. (sammanfattning) Uppsala : Uppsala universitet, 2008. / Härtill 3 uppsatser.
3

Identification and characterization of a NEF associated kinase

Arora, Vivek Kumar. January 2002 (has links) (PDF)
Thesis (Ph. D.) -- University of Texas Southwestern Medical Center at Dallas, 2002. / Vita. Bibliography: 116-128.
4

RegulaÃÃo das guanosina trifosfatases RHO na reduÃÃo da migraÃÃo de cÃlulas intestinais induzida por cepas selvagem e padrÃo de Escherichia coli enteropatogÃnica / Regulation of RHO guanosine triphosphatases in reducing the migration of intestinal cells induced by wild and standard strains of enteropathogenic Escherichia coli

Paloma AraÃjo Cavalcante 28 February 2013 (has links)
Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / FundaÃÃo de Amparo à Pesquisa do Estado do Cearà / Escherichia coli enteropatogÃnica (EPEC) à um importante patÃgeno associado Ãs doenÃas diarreicas. InfecÃÃes intestinais ocasionam comprometimento da barreira intestinal e um dos primeiros mecanismos de resposta à recuperaÃÃo à a migraÃÃo das cÃlulas intestinais. As principais proteÃnas que regulam esse processo sÃo as pequenas GTPases Rho, Rac1, RhoA e Cdc42A. A alanil-glutamina (Ala-Gln) estimula este processo migratÃrio, entretanto os mecanismos envolvidos nesta resposta ainda sÃo desconhecidos. Desse modo, investigou-se o efeito de uma cepa selvagem e padrÃo (E2348/69) de EPEC, e de uma cepa comensal E. coli HS na migraÃÃo celular intestinal, bem como a regulaÃÃo da transcriÃÃo e expressÃo gÃnica das GTPases Rho e o papel da suplementaÃÃo com Ala-Gln no processo de migraÃÃo na presenÃa ou ausÃncia da infecÃÃo. A infecÃÃo pelas cepas de EPEC e pela cepa comensal reduziram significativamente a migraÃÃo celular intestinal. Entretanto, houve uma maior reduÃÃo desse efeito nas cÃlulas infectadas pelas cepas de EPEC quando comparado Ãquelas infectadas pela cepa comensal de E. coli HS. Observou-se um alto percentual de cÃlulas necrÃticas, cerca de 30%, induzido pela cepa padrÃo de EPEC apenas nos tempo de 12 e 24 horas apÃs infecÃÃo. A adiÃÃo da Ala-Gln em cÃlulas nÃo infectadas estimulou significativamente e de modo dose dependente a migraÃÃo apÃs 24 horas. PorÃm, quando esse nutriente foi adicionado durante 12 e 24 horas na presenÃa da infecÃÃo, nÃo houve uma reversÃo do dano. Em relaÃÃo à expressÃo gÃnica das GTPases Rho, observou-se um aumento da transcriÃÃo de rac1 nas cÃlulas que haviam sido infectadas pelas cepas de EPEC e E. coli HS, bem como um aumento da transcriÃÃo de rhoA nas cÃlulas infectadas pela cepa padrÃo de EPEC apÃs 2 horas da infecÃÃo. Todavia, na anÃlise das proteÃnas por imunofluorescÃncia, RhoA e Cdc42 mostraram-se aumentadas nas cÃlulas infectadas pela EPEC padrÃo quando comparado ao controle. Enquanto que as cÃlulas infectadas com a cepa selvagem de EPEC observou-se um aumento de Rac1 e reduÃÃo de RhoA. Esses dados mostraram que a migraÃÃo das cÃlulas intestinais à reduzida principalmente pelas cepas patogÃnicas de EPEC, ao regular a transcriÃÃo e expressÃo gÃnicas das proteÃnas GTPases Rho. A suplementaÃÃo com Ala-Gln em cÃlulas intestinais promoveu a migraÃÃo celular apenas na ausÃncia da infecÃÃo. / Enteropathogenic Escherichia coli (EPEC) is an important pathogen associated with diarrheal diseases. Intestinal infections cause impairment of the intestinal barrier and one of the earliest response mechanisms to recover is migration of the intestinal cells to cover the injured area. The key proteins that regulate cell migration are small Rho GTPases, Rac1, Cdc42 and RhoA. The alanyl-glutamine (Ala-Gln) increases this migration process, however the mechanisms involved in this response are still unknown. Thus, we investigated the effect of a wild type strain and standard (E2348/69) of EPEC strain and a commensal E. coli HS on intestinal cell migration, as well as transcriptional regulation and gene expression of Rho GTPases and the role of supplemental Ala-Gln in the migration process in the presence or absence of infection. Infection by EPEC strains and commensal E. coli HS significantly reduced intestinal cell migration. However, this effect was more pronounced in cells infected by the strains of EPEC compared to those infected by the commensal strain of E. coli HS. We observed a high percentage of necrotic cells, about 30%, induced only by EPEC strain pattern 12 and 24 hours after infection. The addition of Ala-Gln in uninfected cells significantly stimulated in a dose dependent migration after 24 hours. However, when this nutrient was added over 12 and 24 hours in the presence of infection, there was no reversion of the damage. Regarding the gene expression of Rho GTPases, we observed an increase in transcription of rac1 in cells that had been infected by the strains of EPEC and E. coli HS as well as an increase in rhoA transcription in cells infected with EPEC strain pattern at 2 hours after infection. However, the analysis of proteins by immunofluorescence, RhoA and Cdc42 shown to be elevated in cells infected with EPEC pattern when compared to the control. Whereas cells infected with wild EPEC strain was observed an increase of Rac1 and reduction of RhoA. These data showed that cell migration is reduced mainly by the intestinal pathogenic strains of EPEC, in regulating gene transcription and expression of the protein Rho GTPases. Supplementation with Ala-Gln in intestinal cells only promoted cell migration in the absence of infection.
5

Avaliação dos efeitos da inibição da via Rho/Rho-quinase na adesão dos eosinófilos de pacientes com anemia falciforme e no modelo de inflamação pulmonar em camundongos com anemia falciforme / Evaluation of the efects of inhibition Rho/Rho-kinase pathway on eosinophils from sickle cell Anemia patients and lung inflammation in sickle cell anemia mice model

Pallis, Flávia Rubia, 1986- 02 December 2015 (has links)
Orientadores: Carla Fernanda Franco Penteado, Fernando Ferreira Costa / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-26T18:17:52Z (GMT). No. of bitstreams: 1 Pallis_FlaviaRubia_D.pdf: 2236341 bytes, checksum: 3d0b519ba21fcfbc645749dccc82a06a (MD5) Previous issue date: 2015 / Resumo: A vaso-oclusão compreende um processo complexo e multicelular iniciado pela adesão de hemácias e leucócitos ao endotélio ativado, causando a obstrução vascular, ativação de células endoteliais vasculares e lesões que podem induzir uma resposta inflamatória contínua na anemia falciforme (AF). Estudos preliminares mostraram que os eosinófilos de pacientes com AF encontram-se ativados no sangue periférico, porém o envolvimento dessa célula no processo de vaso-oclusão ainda não está bem caracterizado. Pouco se sabe sobre o papel das proteínas da via das Rho GTPases na adesão dos eosinófilos ao endotélio vascular, bem como nas complicações pulmonares da doença. O objetivo desse trabalho foi avaliar in vitro o papel dos eosinófilos e das proteínas pertencentes à família das Rho GTPases na fisiopatologia da AF, e avaliar in vivo o papel dessa via na resposta inflamatória pulmonar induzida pela OVA em camundongos com AF. Sangue periférico de indivíduos saudáveis (controles) e pacientes com AF, em terapia com hidroxiureia (SSHU) ou não (SS), foi coletado para avaliar a adesão estática e em fluxo. A adesão dos eosinófilos de pacientes com AF à HUVEC estimulada com TNF-'alfa' foi significativamente maior quando comparado a adesão dos eosinófilos á HUVEC de indivíduos controle, em condições de fluxo e estática. No entanto, a adesão dessas células à HUVEC estimulada com TNF-? foi menor nos pacientes SSHU, quando comparada com o com aos SS. O pré-tratamento das HUVEC com o inibidor de Rac1, reduziu a adesão dos eosinófilos de pacientes SS ou SSHU. Em condições de fluxo, o número de eosinófilos aderidos à HUVEC reduziu significativamente quando estas foram tratadas com Y-27632 ou NSC23766 nos três grupos avaliados, porém essa inibição foi maior no grupo SS. In vivo a OVA induziu inflamação pulmonar caracterizada pelo aumento na contagem de leucócitos, principalmente eosinófilos, no lavado broncoalveolar dos camundongos. Essa inflamação foi potencializada nos camundongos com AF (Berkeley e Transplantados) quando comparados aos controles (C57BL6). Os camundongos Transplantados apresentaram níveis elevados de mediadores pró-inflamatórios, tais como, IL-4, IL-5, IL-6, IL-13, RANTES, Eotaxina, MCP-1, MMP-9 e TIMP-1 quando comparados aos camundongos do grupo não sensibilizado (NS). Nenhuma diferença foi observada nos níves de RNAm pulmonar das metaloproteinases e seus inibidores quando comparados os camundongos Transplantados do grupo OVA com os NS, porém a expressão de IL-6 é significativamente maior no pulmão dos animais falciformes desafiados com OVA. Na avaliação funcional dos brônquios, os dados mostraram que a potência para metacolina foi maior nos camundongos Berkeley, quando comparados aos Transplantados e ainda maior quando comparados com os C57BL6. Os animais que foram tratados com os inibidores da via RhoA/ROCK, Y-27632 ou Fasudil, apresentaram menor contagem total e diferencial das células que migraram para os pulmões e níveis reduzidos dos mediadores pró-inflamatórios avaliados. O pré-tratamento com o Fasudil reduziu a potência e a resposta máxima para metacolina dos brônquios da linhagem Berkeley. Não foi observada diferença na avaliação funcional da reatividade da traqueia no modelo de asma experimental nos grupos avaliados. Tomados em conjunto, os resultados indicam que a via RhoA/ROCK tem papel importante na adesão dos eosinófilos ao endotélio e que a inibição dessa via pode atenuar a asma associada a doença falciforme. Deste modo, sugerimos que os inibidores dessa via podem ser novos agentes terapêuticos para o tratamento das manifestações clínicas da AF / Abstract: Vaso-occlusion, comprising a complex and multicellular process, initiated by the adhesion of erythrocytes and leukocytes to the activated endothelium, leading to vascular obstruction, activation of vascular endothelial cells and continuous lesions in patients with sickle cell anemia (SCA). Preliminary results demonstrated that eosinophils from SCA patients exist in an activated state, however the participation of this cell in the vasooclusive process in not well establish. The role of proteins via the Rho GTPases in the adhesion of eosinophils to the vascular endothelium and in the pulmonary complications of SCA disease it is unknown. The aim of this study was to evaluate in vitro the role of the eosinophils and proteins belonging to the Rho GTPases family in SCA pathophysiology, and evaluate in vivo the role of this pathway in pulmonary inflammatory responses induced by OVA in SCA mice. Peripheral blood of healthy individuals (controls) and SCA patients in therapy or not with hydroxyurea (SCAHU) was collected for static and flow adhesion experiments. For static adhesion assays, eosinophils were isolated from control subjects or SCA patients on or off HU therapy. Adhesion of SCA eosinophils to HUVEC (Human Umbilical Vein Endothelial Cells) under TNF-'alfa'-stimulated conditions was higher when compared with control eosinophils, in flow conditions and static assay. Furthermore, SCAHU eosinophils demonstrated significantly lower adhesive properties, compared to SCA eosinophils. The adhesion of eosinophils from SCA or SCAHU patients were reduced when HUVEC were pretreated with NSC23766 inhibitor, compared to non-treated HUVEC. Under flow conditions, the number of eosinophils adhered to HUVEC cells was reduced when they were treated with Y-27632 or NSC23766 in the three groups investigated, however this inhibition was higher in the SCA patients. In vivo OVA induced lung inflammation, characterized by increased leukocyte particularly eosinophils, counts in the mice bronchoalveolar fuid (BALF). This inflammation was enhanced in SCA mice (Berkeley and Transplanted) when compared to controls (C57BL6). Transplanted mice showed high levels of pro-inflammatory mediators such as IL-4, IL-5, IL-6, IL-13, RANTES, Eotaxin, MCP-1, MMP-9 and TIMP-1 as compared to the control mice group (NS). Furthermore, the SCA mice induced with OVA showed higher lung gene expression of IL-6; however, there was no difference in the expression of MMP-2, MMP-8, MMP-9, MMP-12, TIMP-1 and TIMP-2, compared to NS. In the functional assessment of the bronchi reactivy, data showed that the potency to methacholine in asthmatic model was was greater in the SCA mice (Berkeley), compared to the Transplanted SCA mice, and even greater when compared to C57BL6. The animals treated with the inhibitors of the RhoA/ROCK pathway, Y-27632 or Fasudil, showed lower total and differential cells counts due to migration to the lungs. Pretreatment with the RhoA/ROCK pathway inhibitor significantly reduced the proinflammatory mediator levels evaluated. Treatment with Fasudil reduced maximal response for methacholine in bronchi from Berkeley model. No significant difference was observed in the tracheal reactivity after OVA challenge in all groups investigated. Taken together, our data indicated that RhoA/ROCK pathway play an important role in the eosinophil adhesion to the endothelium and, the inhibition of this pathway could alleviates asthma in SCA patients. Thus, we suggest that RhoA/ROCK inhibitors represents novel therapeutic agents for the treatment of SCA clinical manifestations / Doutorado
6

Molecular control of endothelial lumen formation by Rho GTPases in three dimensional collagen matrices

Koh, Wonshill. January 2008 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 2008. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Vita. "May 2008" Includes bibliographical references.
7

Investigação do papel do óxido nítrico e de Rho GTPases na adesão de neutrófilos sob condições inflamatórias = Investigation of the role of nitric oxide and Rho GTPases in neutrophils adhesion under inflammatory conditions / Investigation of the role of nitric oxide and Rho GTPases in neutrophils adhesion under inflammatory conditions

Silveira, Angélica Aparecida Antoniellis, 1987- 21 August 2018 (has links)
Orientador: Nicola Amanda Conran Zorzetto / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-21T05:53:22Z (GMT). No. of bitstreams: 1 Silveira_AngelicaAparecidaAntoniellis_M.pdf: 1268408 bytes, checksum: 22c750391706cfa07cb1fd66d9e8a9c1 (MD5) Previous issue date: 2012 / Resumo: Durante a resposta inflamatória, os neutrófilos e outros leucócitos aderem ao endotélio, deixando os vasos sanguíneos e movimentando-se ativamente em direção ao foco inflamatório. A migração dos neutrófilos para sítios inflamatórios depende de uma série de eventos adesivos e quimiotáticos, resultantes da ativação de moléculas de adesão como as selectinas e integrinas e receptores de quimiocinas. Devido às suas propriedades, os neutrófilos podem ser ativados por proteínas de sinalização intracelular, as Rho GTPases, que auxiliam os neutrófilos a desempenhar esta função por interferirem em mudanças no citoesqueleto. Estas proteínas também estão envolvidas na adesão e proliferação celular. Os neutrófilos são capazes de sintetizar óxido nítrico (NO), sendo que esta produção de NO é um importante componente da resposta imune inata durante a inflamação. Estudos demonstraram que os neutrófilos têm papel indutor na geração de inflamação e esforços visando compreender o mecanismo adesivo destas células nos processos inflamatórios podem ser um ponto chave para intervenções farmacológicas em doenças que são caracterizadas por inflamação vascular com consequente obstrução de fluxo sanguíneo. Diante disso, este estudo objetivou avaliar o papel da via do NO e das Rho GTPases no mecanismo pelo qual os estímulos inflamatórios aumentam a adesão de neutrófilos. Também foi avaliado os efeitos da sinvastatina na modulação das propriedades adesivas de neutrófilos, como ferramenta para auxiliar no estudo do envolvimento das Rho GTPases, Rac1 e RhoA, no processo adesivo destas células. Este mecanismo foi estudado a partir de neutrófilos isolados do sangue periférico por ensaios de adesão estática e em fluxo e citometria de fluxo. Além disso, foi analisada a expressão gênica das Rho GTPases, Rac1 e RhoA, através de PCR em tempo real. Sob potente estímulo de TNF-?, as propriedades adesivas dos neutrófilos aumentam significativamente. Inibidores de NO sintase e doadores de NO não alteraram as propriedades adesivas de neutrófilos quando estimulados com TNF-?. Não observamos grande diferença quanto à adesão e expressão das moléculas de adesão na superfície dos neutrófilos usando inibidor de Rac1, porém o composto Y-27632, inibidor de ROCK (Rho-associated coiled coil forming protein serine/threonine kinase), proteína efetora de RhoA, mostrou aumentar a adesão dos neutrófilos sob condições basais. O uso da sinvastatina modulou as propriedades adesivas e a expressão de Mac-1 nos neutrófilos na presença de um estímulo inflamatório, apoiando evidências de seu uso como anti-inflamatório. Em destaque foi observado que o Y-27632 reverteu o efeito da sinvastatina sob estímulo de TNF-? e que o mevalonato e os isoprenóides intermediários da via do colesterol, GGPP e FPP, não foram capazes de reverter o efeito da sinvastatina. Dados indicam que a via de sinalização dependente em NO-GMPc aparentemente não modula as propriedades adesivas dos neutrófilos sob condições inflamatórias. Por outro lado, resultados indicam que as Rho GTPases parecem estar envolvidas na regulação das propriedades adesivas dos neutrófilos sob condições inflamatórias. O envolvimento de ROCK na adesão celular ainda não está completamente compreendido, mas de acordo com nossos resultados podemos sugerir a hipótese de que esta enzima efetora tenha um papel na inducão de adesão dos neutrófilos na presença de um estímulo inflamatório. A sinvastatina foi capaz de inibir as propriedades adesivas de neutrófilos quando ativados indicando mais uma utilidade desta classe de drogas no tratamento de doenças inflamatórias. O papel das Rho GTPases nas propriedades adesivas dos neutrófilos sob condições inflamatórios ainda precisa ser melhor elucidado / Abstract: During the inflammatory response, neutrophils and other leukocytes adhere to the endothelium leaving the blood vessels and actively moving towards the inflammatory focus. The migration of neutrophils to inflammatory sites depends on a variety of chemotactic and adhesive events resulting from the activation of adhesion molecules such as selectins and integrins and chemokine receptors. Due to its properties, neutrophils may be activated by small intracellular signaling proteins, the Rho GTPases, which help neutrophils to fulfill this function by interfering in cytoskeletal changes. These proteins are also involved in cell adhesion and proliferation. The neutrophils are able to synthesize nitric oxide (NO), and this production of NO is an important component of innate immunity during inflammation. Studies have shown that neutrophils play a role in inducing inflammation and generation of efforts to understand the adhesive mechanism exerted by neutrophils in inflammatory processes may be a key point for pharmacological interventions for diseases that are characterized by vascular inflammation with consequent obstruction of blood flow. Thus, this study aimed to evaluate the role of the NO pathway and the Rho GTPases in the mechanism by which inflammatory stimuli increases neutrophil adhesion. We also assessed the effects of simvastatin on neutrophil adhesive properties as a tool to aid in studying the involvement of Rho GTPases, RhoA and Rac1 in these mechansims. Neutrophils were isolated from peripheral blood and aspects of adhesion studied by static and flow adhesion assays as well as flow cytometry. In addition, we analyzed the gene expression of Rho GTPases, Rac1 and RhoA by real time - PCR. Following a strong stimulation with TNF-?, the adhesive properties of neutrophils increase significantly. NO synthase inhibitors and NO donors did not modify the adhesive properties of neutrophils when stimulated with TNF-?. We did not observe any significant differences in the adhesion of neutrophils and the expression of adhesion molecules on their surface in the presence of a Rac1 inhibitor. However, an inhibitor of ROCK (Rho-associated coiled coil forming protein serine/threonine kinase, an efector protin for the RhoA), Y-27632, was shown to increase the adhesion of neutrophils under basal conditions. The use of simvastatin decreased adhesive properties and modulated the expression of Mac-1 of neutrophils in the presence of an inflammatory stimulus, supporting the use of this class of drugs as anti-inflammatory agents. Importantly, the attenuating effects of simvastatin on TNF-? stimulated neutrophil adhesion were reversed by Y-27632, whereas the cholesterol pathway intermediates, mevalonate, and the isoprenoids, GGPP FPP, were unable to reverse the effects of this drug. Data indicate that the NO-cGMP signaling pathway does not appear to modulate the adhesive properties of neutrophils under inflammatory conditions. Moreover, results suggest that Rho GTPases may be involved in the regulat ion of the adhesive properties of neutrophils. The involvement of ROCK in cellular adhesion is not yet fully understood but, according to our findings, it may be hypothesized that this protein effector has a role in the induction of neutrophil adhesion. Simvastatin was able to inhibit the adhesive properties of neutrophils when activated, indicating another use of this class of drugs for the treatment of inflammatory diseases. The role of Rho GTPases in the adhesive properties of neutrophils under inflammatory conditions should be further elucidated / Mestrado / Ciencias Biomedicas / Mestra em Ciências Médicas
8

Using Light to Observe and Control Cellular Function: Improving Bioluminescence Imaging and Photocontrol of Rho GTPase Activation States: A Dissertation

Harwood, Katryn R. 30 September 2011 (has links)
The dynamic processes that occur at specific times and locations in cells and/or whole organisms during cellular division, migration, morphogenesis and development are critical. When these molecular events are not properly regulated, disease states can develop. Tools that can allow us to better understand the specific events that, when misregulated, result in disease development can also allow us to determine better ways to combat such misregulation. Specifically, tools that could allow us to better visualize cellular processes or those that allow us to control cellular functioning in a spatiotemporal manner could present great insight into the detailed inner workings of cells and/or whole organisms. Where chemistry and biology intersect presents a powerful starting point for the development of such tools. The first half of this thesis addresses tools to allow the better visualization of cellular events, in particular the intriguing process of bioluminescence and the work that has been done to better understand and optimize its utilization, particularly in living organisms. The novel work presented here details a parallel approach to improve our ability to observe cellular functioning specifically by improving bioluminescence imaging through the generation and characterization of mutant luciferase proteins that can better utilize novel small molecule luciferin substrates. The second half of this thesis discusses methods that have been developed to better control cellular events through the control of protein activity, specifically a family of proteins called the Rho GTPases. This family’s activation at specific times and locations is essential to proper cellular function and exemplifies the need for spatiotemporal control. Described are methods to control the activation states of the Rho GTPases to probe their cellular roles in a temporal and spatial manner using photosensitive small molecules. Taken together, the findings described herein demonstrate the application of chemistry to allow for the better observation and control of cellular processes, toward the ultimate goal of improving our understanding of the regulatory processes involved in the control of key factors leading to disease states.
9

Roles and regulation of Saccharomyces cerevisiae Rho-type GTPases Rho5p and Cdc42p

Annan, Robert, January 1900 (has links)
Thesis (Ph.D.). / Written for the Dept. of Biochemistry. Title from title page of PDF (viewed ). Includes bibliographical references.
10

Identification and Characteristics of Factors Regulating Hepatocellular Carcinoma Progression and Metastasis: A Dissertation

Ahronian, Leanne G. 28 March 2014 (has links)
Hepatocellular carcinoma (HCC) is a common malignancy of the liver that is one of the most frequent causes of cancer-related death in the world. Surgical resection and liver transplantation are the only curative options for HCC, and tumor invasion and metastasis render many patients ineligible for these treatments. Identification of the mechanisms that contribute to invasive and metastatic disease may enlighten therapeutic strategies for those not eligible for surgical treatments. In this dissertation, I describe two sets of experiments to elucidate mechanisms underlying HCC dissemination, involving the activities of Krüppel-like factor 6 and a particular p53 point mutation, R172H. Gene expression profiling of migratory HCC subpopulations demonstrated reduced expression of Krüppel-like factor 6 (KLF6) in invasive HCC cells. Knockdown of KLF6 in HCC cells increased cell transformation and migration. Single-copy deletion of Klf6 in a HCC mouse model results in increased tumor formation, increased metastasis to the lungs, and decreased survival, indicating that KLF6 suppresses both tumor formation and metastasis in HCC. To elucidate the mechanism of KLF6-mediated tumor and metastasis suppression, we performed gene expression profiling and ChIP-sequencing to identify direct transcriptional targets of KLF6 in HCC cells. This analysis revealed novel transcriptional targets of KLF6 in HCC including CDC42EP3 and VAV3, both of which are positive regulators of Rho family GTPases. Concordantly, KLF6 knockdown cells demonstrate increased activity of the Rho family GTPases RAC1 and CDC42, and RAC1 is required for migration induced following KLF6 knockdown. Moreover, VAV3 and CDC42EP3 are also required for enhanced cell migration in HCC cells with KLF6 knockdown. Together, this work describes a novel signaling axis through which KLF6-mediated repression of VAV3 and CDC42EP3 inhibits RAC1Gmediated HCC cell migration in culture, and potentially HCC metastasis in vivo. TP53 gene mutations are commonly found in HCC and are associated with poor prognosis. Prior studies have suggested that p53 mutants can display gain-of- function properties in other tumor types. Therefore, I sought to determine if a particular hotspot p53 mutation, p53R172H, provided enhanced, gain-of-function properties compared to p53 loss in HCC. In vitro, soft agar colony formation and cell migration is reduced upon knockdown of p53R172H, indicating that this mutation is required for transformation-associated phenotypes in these cells. However, p53R172H-expressing mice did not have enhanced tumor formation or metastasis compared to p53-null mice. These data suggest that p53R172H and p53 deletion are functionally equivalent in vivo, and that p53R172H is not a gain-of-function mutant in HCC. Inhibition of the related transcription factors p63 and p73 has been suggested as a potential mechanism by which mutant p53 exerts its gain-of-function effects. Analysis of p63 and p73 target genes demonstrated that they are similarly suppressed in p53-null and p53R172H-expressing HCC cell lines, suggesting a potential explanation for the phenotypes I observed in vivo and in vitro. Together, the studies described in this dissertation increase our understanding of the mechanisms underlying HCC progression and metastasis. Specifically, we find and characterize KLF6 as a novel suppressor of HCC metastasis, and determine the contribution of a common p53 point mutation in HCC. This work contributes to ongoing efforts to improve treatment options for HCC patients.

Page generated in 0.0601 seconds