Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 4 uppsatser.

Orientador: Karina Gottardello Zecchin / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-16T18:13:14Z (GMT). No. of bitstreams: 1 Ortega_RoseMara_M.pdf: 2975676 bytes, checksum: afd715972fbc788aca5b999d67d862a8 (MD5) Previous issue date: 2010 / Resumo: Ácido graxo sintase (FASN - fatty acid synthase) é a enzima metabólica responsável pela síntese endógena do ácido graxo saturado palmitato, a partir dos precursores acetil-CoA e malonil-CoA. Diversos estudos mostram que, em contraste com a maioria das células normais, FASN é altamente expressa em vários tipos de neoplasias malignas humanas, tais como as de próstata, mama e melanoma sendo que, em alguns destes tumores, a alta expressão de FASN está associada a um pior prognóstico. Anteriormente demonstramos que a inibição específica da atividade de FASN reduz significativamente a proliferação celular e promove a apoptose em linhagem celular de melanoma murino, B16-F10. O objetivo deste trabalho foi investigar de que maneira a inibição farmacológica de FASN reduz a proliferação de células B16-F10, utilizando a cerulenina, um produto natural do fungo Cephalosporium caerulens, como inibidor de FASN. O tratamento com cerulenina reduziu significativamente a proliferação das células B16-F10 de maneira dose-dependente. Ensaios de lipogênese utilizando 3H2O confirmaram a inibição da atividade de FASN pelo tratamento com cerulenina. Tal inibição resultou em significativo bloqueio da proliferação, conforme evidenciado pelo aumento do número de células nas fases G0/G1, assim como redução de células na fase S, em comparação com os controles. Paralelamente, o tratamento com cerulenina também aumentou o número de células em apoptose. Western blottings, feitos a partir de extratos de células tratadas com cerulenina, mostraram aumento significativo da proteína supressora de tumor p21WAF1/Cip1, assim como redução de cdk2, uma Ser/Thr necessária para a transição G1/S, e Skp2, uma proteína necessária para a degradação proteossômica de p27Kip1. Apesar de não ter alterado o conteúdo total de p27Kip1, a inibição de FASN aumentou a quantidade de p27Kip1 co-imunoprecipitada com cdk2. Por outro lado, o tratamento com cerulenina não alterou o conteúdo de outras proteínas envolvidas na progressão das fases G1-S do ciclo celular, tais como cdk4, cdk6, Rb total, ciclina D1 e ciclina E. Em conjunto estes resultados demonstram que a inibição de FASN primeiramente altera os níveis de proteínas envolvidas na transição de G1 para S, tais como p21WAF1/Cip1, p27Kip1 e Skp2, e posteriormente induz apoptose em células de melanoma murino B16-F10 / Abstract: Fatty acid synthase (FASN) is the metabolic enzyme responsible for the endogenous synthesis of the saturated long-chain fatty acid palmitate, from the precursors acetyl-CoA and malonyl-CoA. In contrast to most normal cells, the overexpression of FASN in several human malignancies, such as those of prostate, breast, ovary, melanoma, and soft tissue sarcomas has been associated with poor prognosis. We have previously shown that the specific inhibition of FASN activity significantly reduce proliferation and promote apoptosis in the mouse metastatic melanoma cell line B16-F10. Here we investigated the events involved in cell cycle arrest subsequent to pharmacological FASN inhibition with cerulenin, a natural antifungal antibiotic obtained from Cephalosporium caerulens, in B16-F10 cells. Cerulenin treatment significantly reduced melanoma cells proliferation in a dose dependent manner. Lipogenesis using 3H2O confirmed inhibition of FASN activity after cerulenin treatment. Such enzymatic inhibition culminated in cell cycle arrest, evidenced by a significant increase in G0/G1 phase, as well as decline of the S phase, in comparison with untreated cells. Cerulenin treatment also induced apoptosis in B16-F10 tumor cells. Western blotting analysis of cerulenin-treated cells showed a significant accumulation of the tumor suppressor proteins p21WAF1/Cip1 and p27Kip1, together with decreased amounts of cdk2, a Ser/Thr protein kinase necessary for the G1/S transition, and Skp2, essential for the proteasomal degradation of p27Kip1. Cerulenin treatment increased the levels of p27Kip1 co-immunoprecipitated with cdk2, despite western blotting analysis showed similar content of total p27Kip1. The levels of other proteins involved in G1/S cell cycle progression, such as cdk4, cdk6, total Rb, cyclins A and E, were not affected by FASN inhibition. Collectively these findings suggest that FASN inhibition first modify the levels of proteins involved in transition G1-S, as p21WAF1/Cip1, p27Kip1 and Skp2, to finally induce apoptosis in mouse melanoma B16-F10 cells / Mestrado / Estomatologia / Mestre em Estomatopatologia

Thesis advisor: Thomas C. Chiles / Normal B lymphocytes require extrinsic factors to grow and proliferate. Surface receptors (e.g., B-cell antigen receptor, BCR) function, in part, to link growth factors to signal transduction/metabolic pathways and the cell cycle machinery. Accumulating evidence indicates that signal transduction-dependent changes in both glucose energy metabolism and de novo transcription of the D-type cyclin-cdk4/6 pathway are necessary for quiescent B-lymphocytes to enter G1-phase of the cell cycle and grow. B cell growth represents a critical checkpoint for subsequent proliferation and clonal expansion of antigen-specific lymphocytes. On the former, we have shown earlier that acquisition of extracellular glucose and metabolism via the glycolytic pathway is required for conventional splenic B-2 lymphocytes to grow (i.e., increase cell size and mass) in response to antigen challenge; however, the metabolic fate and biological significance of glucose-derived carbons are unknown. Here, we show that in response to BCR ligation, glucose carbon flow is directed into a de novo lipogenic pathway that is regulated, in part, via phosphoinositide-3 kinase (PI-3K)-dependent activation of ATP citrate lyase (ACL), a key rate-limiting enzyme in de novo lipogenesis. Inhibition of ACL results in a loss of B-cell growth and cell viability. Regarding the latter point, the B-1a lymphocyte subset expresses cyclins D2 and D3 that are transiently expressed in a non-overlapping manner, notably cyclin D3 expression immediately precedes the G1/S phase transition, suggesting distinct functions for these D-type cyclins in B-1a lymphocyte G0-to-S phase progression. We show herein that murine B-1a cells deficient in cyclin D3 proliferate normally in response to extracellular stimuli, in part, due to a compensatory sustained up-regulation of cyclin D2. In keeping with this, human diffuse large B-cell lymphoma (DLBCL) represents a malignant clonal expansion of B cells characterized by several subsets, including germinal center (GC) and activated B-cell (ABC) types. Here, we show that the GC-type LY18 human DLBCL exhibits constitutive expression of cyclin D3, but not cyclins D1 and D2. Targeting of cyclin D3-holoenzyme complexes with cell permeable chemical- and peptide-based cdk4 inhibitors results in G1-phase arrest and apoptosis via a pathway that involves inhibition of pRb phosphorylation. By contrast, endogenous knock down of cyclin D3 with siRNA did not induce growth arrest or apoptosis, in part, due to redundancy with cyclin E. / Thesis (PhD) — Boston College, 2009. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Biology.

O estudo do díptero Rhynchosciara americana forneceu informações importantes sobre a biologia cromossômica, por apresentar cromossomos politênicos e amplificação gênica em diferentes órgãos. Dentre os órgãos que apresentam especializações do ciclo celular, o ovário é um dos mais interessantes, possuindo características únicas, como o desenvolvimento sincrônico dos folículos ovarianos e o fato de apresentar uma única e gigante célula nutridora conectada ao ovócito através de um canal citoplasmático. Une em si: meiose no ovócito, célula nutridora com poliploidia seguido de politenia e células foliculares com mitose. Células poliplóides e politênicas possuem cópias extras de DNA genômico através de repetidos ciclos de fase S sem que ocorra a divisão celular, um processo denominado endoreplicação. Os ciclos celulares, são dirigidos pela oscilação da ativação de complexos ciclina/Cdk. Estudos mostraram que a ciclina A atua em células endoreplicativas em Drosophila e a ciclina B inibe ciclos endoreplicativos induzindo a divisão celular. Torna-se relevante investigar a associação dessas moléculas reguladoras do ciclo celular com os ciclos endoreplicativos que ocorrem na ovogênese de R. americana. Perfis de expressão das ciclinas A e B foram detectados nos ovários por RT-PCR ao longo do desenvolvimento. Ensaios de incorporação do nucleosídeo timidina mostraram elevada atividade proliferativa das células foliculares para formar o folículo e o fim da atividade endoreplicativa nas células nutridoras em pupas de 4 dias. Preparações de imunolocalização proteica em ovários na fase de pupa revelaram acúmulo de ciclina A no citoplasma das células nutridoras e dos ovócitos, e acúmulo de ciclina B no citoplasma e na vesícula germinal do ovócito, atuando nos mecanismos meióticos. O estudo de proteínas relacionadas ao ciclo celular nesse modelo é importante para um melhor entendimento dos ciclos celulares incomuns presentes em diferentes órgãos de insetos. / Study of the diptera Rhynchosciara americana has provided important information about chromosome biology, for it displays polytene chromosomes and gene amplification in different organs. Among the organs that possess cell cycle specializations, the ovary is one of the most interesting ones, showing unique characteristics, such as the synchronous development of follicles and the presence of a single giant nurse cell connected to the oocyte through a cytoplasmic channel. This organ gathers: meiosis in the oocyte, nurse cell with polyploidy followed by polyteny, and follicle cells in mitosis. Polyploid and polytene cells have extra copies of genomic DNA obtained via sequential cycles of S phase not followed by cell division, a process called endoreplication. Cell cycles are driven by the oscilation in the activation of different cyclin/CDK complexes. Studies have shown that Cyclin A acts in endoreplicating cells in Drosophila and Cyclin B inhibits endoreplicative cycles, inducing cell division. Thus, it is relevant to investigate the association between these cell cycle-regulating proteins and the endoreplication cycles that occur during the oogenesis of R. americana. Expression profiles of cyclins A and B were evaluated in the ovary via RT-PCR throughout the development. Thymidine nucleoside incorporation assays showed high proliferative activity in follicle cells to build the follicle and the end of endoreplicative activity in nurse cells of 4-day-old pupae. Protein immunolocalization in ovary at the stage of pupa has shown accumulation of Cyclin A in the cytoplasm of nurse cells and oocytes, and accumulation of Cyclin B in the cytoplasm and germinal vesicle of the oocyte, acting on meiosis mechanisms. The study of proteins related to cell cycle in this model is important for a better understanding of uncommon cell cycle in different insect organ.

Introdução: A identificação de mecanismos genéticos envolvidos no processo de carcinogênese do câncer colorretal levou ao surgimento de novas estratégias terapêuticas como a terapia gênica. Através do bloqueio ou estímulo de determinados alvos genéticos ou moleculares seria possível interromper o ciclo celular de células transformadas. Uma das estratégias sugeridas foi a utilização de seqüências anti-sense do gene da ciclina G que revelou resultados iniciais clínicos e experimentais promissores em diversas neoplasias, inclusive na colorretal. Assim seria esperado que a expressão da ciclina G estivesse freqüentemente alterada de maneira seletiva nas células do câncer colorretal quando comparado às células normais. Por estas razões, decidiu-se estudar a expressão da ciclina G em pacientes com câncer do reto. Métodos: Dados clínicos, epidemiológicos, anátomo-patológicos e de sobrevivência de 36 pacientes com câncer do reto foram obtidos e correlacionados com os resultados de expressão imunohistoquímica da ciclina G. O tecido neoplásico e normal distante da lesão primária foram submetidos a reação imunohistoquímica com anticorpo monoclonal anti-ciclina G e quantificados através de três métodos: (1) quantitativo, obtido a partir da contagem de células determinando a razão entre o número de células positivas e o número total de células contadas em 10 campos; (2) semi-quantitativo (cruzes), obtido a partir da pontuação em sistema de cruzes conforme a intensidade e quantidade de células positivas em áreas de maior impregnação do corante; (3) semi-quantitativo (escore), obtido a partir da pontuação em sistema de escore (alto ou baixo) conforme a intensidade e quantidade de células positivas em áreas de maior impregnação do corante. O estudo estatístico incluiu teste T de student, Qui-quadrado, exato de Fisher, teste t pareado, Wilcoxon, log-rank e curva ROC sendo considerados significativos quando o valor de p<0,05. Resultados: A expressão da ciclina G foi positiva em 76,5±30% da células contadas, com média de 3,2±1,1 cruzes e escore alto em 32 pacientes no tecido tumoral. No tecido normal dos pacientes a positividade foi de 42,2±27,4%, com média de 1,9±1,1 cruzes e escore alto em 16 casos. Quando comparados os tecidos tumoral e normal de cada paciente, o resultado tumor>normal foi obtido em 28 (77,8%) pacientes (quantitativa), 27 (75%) pacientes (semi-quantitativa/cruzes) e 18 (50%) pacientes (semi-quantitativa/escore). A diferença de expressão entre tecido tumoral e tecido normal maior que 10% apresentou correlação com ausência de metástases sistêmicas enquanto que a diferença maior que 38% apresentou correlação com a ausência de metástases linfonodais (área da curva 0,69 nos dois casos). Houve correlação entre o resultado tumor>normal e a ausência de metástases linfonodais quando o método de quantificação foi semi-quantitativo (cruzes e escore;p=0,02 e 0,04). Não houve correlação entre o resultado tumor>normal e as demais características. Não houve influência do resultado tumor>normal nas curvas de sobrevivência (3 anos). Conclusões: A expressão da ciclina G é maior no tecido neoplásico do câncer colorretal quando comparada ao tecido normal. Apesar disso, a expressão da ciclina G é raramente nula no tecido normal. A expressão de ciclina G tumor>normal esteve associada a ausência de metástases linfonodais quando mensurada através de métodos semi-quantitativos. Apesar disso, a expressão alterada da ciclina G não tem influência sobre sobrevivência precoce em pacientes com câncer do reto. / Introduction: Identification of genetic mechanisms involved in colorectal cancer carcinogenesis led to the development of new treatment strategies such as gene therapy. The aim of this strategy is to interrupt cell-cycle of transformed malignant cells by blocking or stimulating specific gene expression. Utilization of cyclin G antisense constructs has been suggested with clinical and experimental promising results in various neoplasias, including colorectal cancer. In this setting, one would expect that cyclin G would be selectively overexpressed in colorectal cancer cells as opposed to normal tissue. For this reason, we decided to study cyclin G expression in patients with rectal cancer. Methods: Clinical, epidemiological, pathological and survival data from 36 patients with rectal cancer was collected and correlated with Cyclin G immunohistochemical expression. Neoplastic and non-adjacent normal tissue were stained with monoclonal anti-Cyclin G antibody and quantified according to 3 different methods: (1) quantitative, obtained from cell count and determined by the ratio between positive counted cells and total number of counted cells observed in 10 microscopic fields; (2) semi-quantitative (crosses), obtained from a scoring system that takes into account both quantity and intensity of most strongly stained areas; (3) semi-quantitative (score), obtained from a scoring system that takes into account both quantity and intensity of most strongly stained areas. Statistical analysis included ROC curves, student\'s T, Chi-square, Fisher\'s exact, log rank, Wilcoxon, and paired t test. Significant differences were considered for p<0.05. Results: In tumor-tissue, positive Cyclin G expression was observed in 76.5±30% of counted cells, with a mean number of 3.2±1.1 crosses and high expression score in 32 patients (89%). In normal tissue, positive cyclin G expression was observed in 42.2±27.4% of counted cells, with a mean of 1.9±1.1 crossed and high expression score in 16 patients. When comparing tumor and normal tissue within each patient, a result of tumor>normal cyclin G expression was observed in 28 (77.8%) patients (quantitative method), 27 (75%) patients (semi-quantitative crosses) and 18(50%) patients (semi-quantitative score). A difference of cyclin G expression between tumor and normal tissue greater than 10% was associated with the absence of metastatic disease. A difference of cyclin G expression between tumor and normal tissue greater than 38% was associated with the absence of lymph node metastases (ROC curve area of 0.69 in both cases). There was significant association between cyclin G expression tumor>normal result and the absence of lymph node metastases when using semi-quantitative quantification methods (p=0.02 for crosses; p=0.04 for score). There was no association between cyclin G expression and other patient\'s characteristics or survival. Conclusion: Cyclin G expression is greater in tumor tissue when compared to normal tissue in patients with rectal cancer. However, cyclin G expression in normal tissue is rarely absent. Tumor>normal cyclin G expression is significantly associated with absence of lymph node metastases when quantified using semiquantitative methods. However, cyclin G expression had no influence in short-term survival.

La famille des protéines IMPs (IGF2 mRNA binding proteins) compte trois membres IMP1, 2 et 3. Les IMPs participent au développement embryonnaire. IMP1 et IMP3 sont considérées comme des protéines oncofoetales. En effet, malgré leur faible expression dans les tissus adultes, elles se retrouvent fortement surexprimées dans des cellules tumorales. Malgré la forte homologie entre les membres de la famille, les IMPs présentent des différences fonctionnelles qui restent très mal comprises jusqu’à présent. De nombreuses études montrent que la protéine IMP3 est très abondante dans de nombreux cancers tels que les carcinomes utérin, rénal, pulmonaire, les hépatocarcinomes et les rhabdomyosarcomes. Ces dernières années, IMP3 est devenu un marqueur de mauvais pronostique pour les patients atteins de cancer. Au cours de ma thèse j’ai principalement travaillé sur une lignée cellulaire de rhabdomyosarcomes (RMS). Les RMS sont des tumeurs principalement pédiatriques mais qui peuvent survenir à tout âge. En outre, la moitié des patients atteints des RMS meurent dans l'année suivant leur rechute et 90% des patients meurent dans les cinq ans suivant leur rechute. De nouvelles approches thérapeutiques sont absolument nécessaires. Mon sujet de thèse consiste à comprendre par quels mécanismes moléculaires les IMPs participent au processus oncogénique des RMS embryonnaires (eRMS). Pour cela, je me suis intéressée à la régulation des cyclines par les IMPs. Dans le cadre de mon projet, j’ai étudié l’effet des IMPs sur trois cyclines différentes : D1, D3 et G1. J’ai montré qu’IMP3, à la différence des deux autres, est capable de contrôler l’expression des cyclines D1, D3 et G1 dans les eRMS, ainsi que dans huit autres lignées de cancer humain différentes. Cette régulation a également des effets sur le cycle cellulaire des eRMS, expliquant l’importance d’IMP3 dans les cancers. Par diverses approches biochimiques, j’ai démontré que, sur les trois IMPs, seule IMP3 est très enrichie dans le noyau des eRMS, dans lequel elle forme des complexes avec les ARNm des CCND1, D3 et G1. Les différents résultats obtenus suggèrent un modèle selon lequel ces interactions au sein du noyau semblent indispensables à la régulation de la traduction des trois cyclines en protégeant leurs ARNm du complexe de silencing RISC (RNA induced silencing complex) et constituent donc la clé du mécanisme par lequel IMP3 contrôle la prolifération des cellules cancéreuses. / RNA-binding proteins of the IMP family (IGF2 mRNA-binding proteins 1-3) are key post-transcriptional regulatory factors of gene expression. They are known to control cell motility, adhesion, and proliferation. In our previous work, we show that all three IMP proteins can directly bind the mRNAs of cyclins D1, D3, and G1 (CCND1, D3, and G1) in vitro. Nevertheless, only IMP-3 regulates their expression in a significant manner in vivo, thus controlling proliferation of a number of human cancer cell lines. Importantly, the nuclear localization of IMP-3 is essential for the post-transcriptional regulation of the expression of CCND1, CCND3, and CCNG1 (CCNs). To elucidate the molecular mechanisms of IMP-3- specific regulation, we have identified its protein partners in human embryonic rhabdomyosarcoma (RMS) cells. We now show that in the nucleus and in the cytoplasm, IMP-3 interacts with a number or RNA-binding nucleocytoplasmic proteins, including DHX9, PTBP1, NF90, NF110, HNRNPA1, HNRNPA2/B1 and HuR. These IMP-3 partners have a dramatic impact on the protein levels of the cyclins. Interestingly, the decrease of CCNs protein synthesis in IMP-3 depleted cells can be fully reversed by down-regulating the key proteins of RNAi machinery, such as AGO2 and GW182. These findings suggest that IMP-3- dependent RNP complexes pre-assembled in the nucleus can protect their target mRNAs from cytoplasmic RNAi-dependent repression in human cancer cells.

Access to abstract restricted until 12/14/2014. / Access to thesis restricted until 12/14/2014. / Department of Biology

Diss. (sammanfattning) Stockholm : Karol. inst., 2002. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 3 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.