Thesis (Ph.D)--University of Tennessee Health Science Center, 2008. / Title from title page screen (viewed on July 16, 2007). Research advisor: Mary-Ann Bjornsti, Ph.D. Document formatted into pages (xii, 123 p. : ill.). Vita. Abstract. Includes bibliographical references (p. 118-123).

Thesis (Ph.D.)--University of Tennessee Health Science Center, 2007. / Title from title page screen (viewed on July 29, 2008). Research advisor: Mary-Ann Bjornsti, Ph.D. Document formatted into pages (xiii, 175 p. : ill.). Vita. Abstract. Includes bibliographical references (p. 161-175).

SOARES, Bruno Marques. Hellebrigenina, um bufodienolídeo com potencial ação compatível de inibidor catalítico da Topoisomerase II. 2013. 85 f. Dissertação (Mestrado em Farmacologia) - Universidade Federal do Ceará. Faculdade de Medicina, Fortaleza, 2013. / Submitted by denise santos (denise.santos@ufc.br) on 2013-08-28T15:47:03Z No. of bitstreams: 1 2013_dis_bmsoares.pdf: 2334333 bytes, checksum: 332b2a9235ebad6d7da12ab6ac20ee16 (MD5) / Approved for entry into archive by denise santos(denise.santos@ufc.br) on 2013-08-28T15:49:37Z (GMT) No. of bitstreams: 1 2013_dis_bmsoares.pdf: 2334333 bytes, checksum: 332b2a9235ebad6d7da12ab6ac20ee16 (MD5) / Made available in DSpace on 2013-08-28T15:49:38Z (GMT). No. of bitstreams: 1 2013_dis_bmsoares.pdf: 2334333 bytes, checksum: 332b2a9235ebad6d7da12ab6ac20ee16 (MD5) Previous issue date: 2013 / Bufodienolides are cardioactive steroids of 24 carbons, originally isolated from a frog’s skin extract of the family Bufonidae used in Chinese medicine. Bufodienolides shows many biological activities, including anticancer activities. Related to antitumor activity, the bufodienolídeos has been shown to inhibit the growth of several human cancer cell lines by inducing apoptosis and cell cycle arrest. This study evaluated the potential cytotoxicity and genotoxicity of six bufodienolides, in six human tumor cell lines, three normal murine lineages and PBMC (peripheral blood mononuclear cells). All six bufodienolides were cytotoxic to all cell lines and tumor PBMC with IC50 values ranging from 0.002 to 3.17 µM. Bufodienolides showed no cytotoxicity for normal murine strains. Thus, the compound hellebrigenin was chosen to determine the action mechanism involved, a sequence of in vitro experiments were performed using HL-60 leukemia cell line. Cells were treated at different concentrations of hellebrigenin (0.03, 0.06 and 0.12 µM) for 24 hours. Cell viability (viable cell number and membrane integrity) HL-60 assessed by flow cytometry showed that the number of cells decreased from the lower concentration (0.03 µM) tested and the percentage of cells with reduced membrane integrity from 0.06 µM concentration. Morphological analysis by flow cytometry revealed increased apoptotic cells starting at concentrations of 0.06 µM. The analysis of nuclear content, showed an increase in DNA fragmentation indicative of sub-G1 apoptosis and accumulation of cells in G2 / M phase from the concentrations of 0.03 and 0.06 µM, respectively. Other tests by flow cytometry revealed that there was an externalization of phosphatidylserine, mitochondrial depolarization, activation of caspase 8 and initiating subsequent activation of effector caspases 3 and 7. These data indicate a cytotoxic mechanism induced by over an apoptotic pathway. Hellebrigenin was not able to cause DNA damage in HL-60 and PBMC nor the emergence of chromosomal aberrations in PBMC. Through the studies of molecular docking was possible to predict the connection between hellebrigenina and human topoisomeraseIIα, showing a result that is compatible with a possible inhibition of this enzyme. Overall, the results indicate the potential cytotoxicity of hellebrigenin. / Os bufodienolídeos são esteróides cardioativos de 24 carbonos, isolados originalmente de um extrato de pele de sapos da família Bufonidae utilizado na medicina chinesa. Os bufodienolídeos possuem grande variedade de atividades biológicas, incluindo atividades antineoplásicas. Em relação à atividade antitumoral, os bufodienolídeos tem demonstrado inibir o crescimento de várias linhagens de células cancerígenas humanas por induzir apoptose e parada do ciclo celular. O presente estudo avaliou o potencial citotóxico e genetóxico de seis bufodienolídeos em seis linhagens tumorais humanos, três linhagens murinas normais e células mononucleadas do sangue periférico (CMSP) humano. Todos os seis bufodienolídeos foram citotóxicos para todas as linhagens tumorais e CMSP com valores de IC50 variando entre 0,002 e 3,17 µM. Os bufodienolídeos testados não apresentaram citotoxicidade para linhagens murinas normais. Desta forma, o composto hellebrigenina foi escolhido para se determinar o mecanismo de ação envolvido. Uma sequência de experimentos in vitro foram realizados utilizando-se a linhagem leucêmica HL-60. As células foram tratadas em diferentes concentrações da amostra hellebrigenina (0,03, 0,06 e 0,12 µM) por 24 horas. A viabilidade das células (número de células viáveis e integridade de membrana) HL-60 avaliada por citometria de fluxo, mostrou que o número de células reduziu a partir da menor concentração (0,03 µM) testada e a porcentagem de células com membrana integra reduziu a partir da concentração 0,06 µM. A análise morfológica por citometria de fluxo revelou aumento de células com padrão apoptótico a partir da concentração de 0,06 µM. Já a análise do conteúdo nuclear, nos mostrou aumento de fragmentação de DNA sub-G1 indicativo de apoptose e acúmulo de células na fase G2/M a partir das concentrações de 0,03 e 0,06 µM, respectivamente. Outros testes por citometria de fluxo revelaram que houve externalização da fosfatidilserina, despolarização mitocondrial, ativação da caspase iniciadora 8 e consequente ativação das caspases efetoras 3 e 7. Estes dados indicam um mecanismo citotóxico por indução de mais de uma via apoptótica. Hellebrigenina não foi capaz de causar danos ao DNA de HL-60 e de CMSP e nem o surgimento de aberrações cromossômicas em CMSP. Por meio dos estudos de docking molecular foi possível predizer a ligação entre hellebrigenina e topoisomeraseIIα humana, resultado compatível com a possível inibição dessa enzima. De forma geral, os resultados apontam o potencial citotóxico do bufodienolídeo hellebrigenina.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / A busca por novos derivados citotÃxicos da nor-β-lapachona à parte de uma crescente e contÃnua busca por novos compostos ativos. O presente estudo teve como objetivo avaliar o potencial citotÃxico de quatro derivados arilaminos (1-4) da nor-β-lapachona e os provÃveis mecanismos envolvidos na citotoxicidade da nor-β-lapachona e de seus derivados. TrÃs derivados (1, 3 e 4) e seu precursor apresentaram elevado potencial citotÃxico sobre todas as linhagens celulares tumorais humanas utilizadas. Em estudos com cÃlulas nÃo tumorais (CMSP), a nor-β-lapachona nÃo induziu citotoxicidade, porÃm seus derivados apresentaram efeitos antiproliferativos, cuja intensidade variou de moderado a fraco com valores de CI50 iguais a 5,02 ÂM (1), 12,02 ÂM (3) e 10,65 ÂM (4). AlÃm disso, os compostos nÃo apresentaram efeitos hemolÃticos (EC50 > 219,29 ÂM). Tanto a nor-β-lapachona quanto seus derivados (1, 3 e 4) induziram apoptose (via mitocondrial) em cÃlulas HL-60, como observado atravÃs dos ensaios de anÃlises morfolÃgicas e de citometria de fluxo, e distÃrbios sobre a progressÃo do ciclo celular de cÃlulas HL-60, apenas na maior concentraÃÃo (4 ÂM). O tratamento com os compostos induziu a formaÃÃo de EROS, assim como quebras das fitas da molÃcula de DNA em cÃlulas HL-60 (NQO1−) e DU-145 (NQO1+). A co-administraÃÃo de GSH reduziu a sensibilidade celular aos efeitos tÃxicos dos compostos estudados, e o prÃ-tratamento com agentes antioxidantes (NAC e IK) reduziu drasticamente a produÃÃo de radicais livres, o mesmo nÃo ocorrendo com culturas prÃ-tratadas com BH (agente depletor de GSH). PorÃm, o dicumarol (inibidor de NQO1) preveniu a formaÃÃo de EROS e os efeitos genotÃxicos apenas na linhagem DU-145, indicando que esses compostos possam ser metabolizados por outras redutases que nÃo a NQO1. As lesÃes ao DNA de cÃlulas DU-145 promovidas pela nor-β-lapachona e seus derivados (1, 3 e 4) foram, parcialmente, reparadas apÃs um perÃodo de tempo de 24 horas, o que corrobora com a sÃntese nÃo programada de DNA detectada apÃs a exposiÃÃo a esses compostos. AlÃm disso, todos os compostos ativos interferiram sobre os processos de reparo dos danos ao DNA induzidos pelo MMS, o que indica que a interferÃncia sobre esses processos contribui para seus efeitos citotÃxicos. A nor-β-lapachona e seus derivados arilaminos (1, 3 e 4) inibiram a taxa de proliferaÃÃo de cepas de S. cerevisiae defectivas na expressÃo de topoisomerases (Top1Δ, Top3Δ e Top1ΔTop3Δ) de maneira mais pronunciada do que observado na cepa selvagem (BY4741), indicando que a interferÃncia sobre a atividade das topoisomerases influencia, de algum modo, a citotoxicidade desses compostos. Nos estudos de genotoxicidade e mutagenicidade com fibroblastos de pulmÃo de hamster chinÃs (linhagem V79), todos os compostos citotÃxicos promoveram quebras nas fitas de DNA, oxidaÃÃo de bases nitrogenadas e induÃÃo de micronÃcleos, em concentraÃÃo (10 ÂM) muito superior do que as necessÃrias para induzir os mesmos eventos em cÃlulas tumorais. ReforÃando a participaÃÃo de EROS sobre os eventos mutagÃnicos, o prÃ-tratamento com NAC preveniu a formaÃÃo de cÃlulas micronucleadas e reduziu a sensibilidade celular aos efeitos tÃxicos dos compostos estudados. Esses resultados ressaltam as propriedades antitumorais da nor-β-lapachona e seus derivados arilaminos e que eles podem ser considerados como protÃtipos para o desenvolvimento de novos agentes anticÃncer. / The search for new cytotoxic derivatives of nor-β-lapachone is part of a growing and continuous search for new active compounds. The present study aimed to evaluate the cytotoxic potential of four arylamino-nor-β-lapachone derivatives (1-4) and the probable mechanism involved in the cytotoxicity of these compounds. Among the tested derivatives, only three of them (1, 3 and 4) and the precursor molecule elicited a significant antiproliferative effects in all human tumor cell lines used in the study. In experiments with peripheral blood mononuclear cells (PBMC), nor-β-lapachone did not induce cytotoxicity, however its derivatives showed antiproliferative effects whose intensity ranged from moderate to weak, with IC50 values equal to 5.02 ÂM (1), 12.02 ÂM (3) and 10.65 ÂM (4). Moreover, all the compounds showed no hemolytic effects (EC50> 219.29 ÂM). Nor-β-lapachone and its derivatives (1, 3 and 4) induced apoptosis (mitochondrial pathway) in HL-60 cells, based upon morphological and flow cytometric analysis, and interference on HL-60 cell cycle progression, only at the highest concentration (4 ÂM). Compounds exposure induced intracellular ROS generation, as well as DNA strand breaks in HL-60 (NQO1−) and DU-145 (NQO1+) cell lines. The co-administration of GSH reduced the cellular sensibility to the toxic effects of the studied compounds. Unlike cells pre-treated with BH (glutathione depletor agent), cells pre-exposed to antioxidants agents (NAC or KI) showed low production of free radicals. On the other hand, dicoumarol (NQO1 inhibitor) prevented the ROS formation and DNA strand breaks only in DU-145 cells, indicating that these compounds can be metabolized by other reductases than NQO1. The DNA damage induced by nor-β-lapachone and its derivatives (1, 3 and 4) in DU-145 cells were partially repaired after 24 h, which agrees with the data of unscheduled DNA synthesis. In addition, all active compounds interfere with DNA repair processes of DNA damage induced by MMS, indicating that this action contributes to compounds cytotoxic effects. All active compounds inhibited the proliferation rate of S. cerevisiae strains defective in the expression of DNA topoisomerases (Top1Δ, Top3Δ and Top1ΔTop3Δ) more pronounced than that observed in wild type strain (BY4741), suggesting that the interference on topoisomerases activities may contributes to the cytotoxicity of active compounds. Genotoxicity and mutagenicity studies with Chinese hamster lung fibroblast cell line (V79), showed that all cytotoxic compounds promoted DNA strand breaks, DNA bases oxidation and micronucleus formation in a concentration (10 ÂM) far higher than needed to induce the same events in tumor cells. Strengthening the ROS contribution on the mutagenic events, the pre-treatment with NAC prevented the formation of micronucleated cells and reduced the V79 cell sensibility to the cytotoxic effects of the studied compounds. These findings underscore the antitumor properties of nor-β-lapachone and its arylamino derivatives and they can be considered as prototypes for the development of new anticancer agents.

Made available in DSpace on 2015-07-22T20:50:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-03-26. Added 1 bitstream(s) on 2015-08-11T03:25:45Z : No. of bitstreams: 1 Publico-10807.pdf: 786945 bytes, checksum: a640250d88b5bd045dc6f2f53834bd45 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Objetivos: Estudar a expressao imuno-histoquimica de topoisomerase IIƒ¿ e de caspase-3 ativada, marcadores de proliferacao e de apoptose, respectivamente, a deteccao de DNA HPV e a evolucao da lesao cervical em mulheres portadoras de lesao intra-epitelial escamosa de baixo grau (LBG). Metodos: Foram avaliadas 40 mulheres portadoras de LBG e 32 sem neoplasia cervical, diagnosticadas por exame cito-colpo-histopatologico, quanto a imunoexpressao de topoisomerase IIƒ¿ e de caspase-3 ativada e quanto a deteccao de DNA HPV por PCR consensual (GP5+/GP6+) em material de esfregaco cervico-vaginal. Os achados foram relacionados as variaveis clinicas das pacientes e a evolucao clinica das lesoes cervicais em 12 meses. As pacientes assinaram termo de consentimento livre e esclarecido. Resultados: A media percentual de celulas imunomarcadas por topoisomerase foi de 11,71% e 4,13%, no grupo com LBG e controle, respectivamente, com diferenca estatisticamente significante. Observou-se que houve expressao de caspase-3 em 17 (42,5%) e em 5 (15,63%) pacientes com e sem LBG, respectivamente, com diferenca estatisticamente significante. Foi detectado HPV DNA em 65% das pacientes com LBG e em 59,4% das pacientes sem lesao cervical, sem relacao com a expressao de topoisomerase IIƒ¿ ou caspase-3. Na presenca de DNA-HPV, a expressao de topoisomerase IIƒ¿ no grupo com LBG foi significativamente maior do que em fragmentos sem lesao. Nao foi observada diferenca quanto a evolucao da lesao cervical em 12 meses de acordo com a imunoexpressao de topoisomerase IIƒ¿. Com relacao a caspase-3 ativada, a maioria das pacientes com imuno-histoquimica negativa teve regressao da lesao cervical. Conclusoes: A imunoexpressao de topoisomerase IIƒ¿ e de caspase-3 ativada podem ser considerados marcadores de proliferacao e de apoptose em lesao cervical de baixo grau, sem relacao com a presenca de DNA-HPV. / Purpose: To evaluate the correlation between the expression of topoisomerase II alpha, active caspase-3 and infection with human papillomavirus in low-grade cervical intraepithelial lesion and in the normal cervix, and whether they might influence susceptibility to, or evolution of, cervical lesion. Patients and methods: Forty cervical biopsies patients with low-grade cervical intraepithelial lesion and thirty-two with normal cervix were stained by immunohistochemistry for topoisomerase IIá and active caspase-3 and were investigated for the presence of HPV on exfoliated cells by general primer GP5+/6+ PCR amplification of DNA. These findings were correlated with clinicopathological features of the patients including their clinical outcome after twelve months. Subjects provided written informed consent. Results: Low-grade CIN patients as a group had a significantly higher expression of topoisomerase II alpha compared to controls, without correlation to disease outcome at 12 months. Caspase-3 was expressed in 42.5% of CIN patients and in 15.63% without disease, and most of women without caspase-3 receded cervical lesion. HPV DNA testing was positive in 65% of the patients with cervical lesion, and in 59.4% of the control group and was not associated to the expression of topoisomerase IIá or active caspase-3. In the presence of a positive HPV DNA testing, women with cervical lesion had a significantly higher expression of topoisomerase II alpha compared to controls. Conclusion: Topoisomerase II alpha and active caspase-3 might be useful diagnostic and prognostic markers in low-grade cervical lesions, delaying a better follow-up. / CNPq: 134106/2005-9 / TEDE / BV UNIFESP: Teses e dissertações

Maintenance of a topological homeostasis by introduction and removal of the supercoils to relieve excessive strain on the DNA is a hallmark of topoisomerase function in the cell. The requirement of the topoisomerases during DNA transaction processes marks a ubiquitous presence of the enzymes in all the life forms. Different reactions carried out by the enzymes include relaxation of positive and negative supercoils required majorly during DNA replication and transcription, decatenation at the end of DNA replication to separate the daughter chromosomes and removal of lethal knots generated in the circular chromosome. In eubacteria, the enzymes introduce negative supercoils to facilitate easier strand separation for DNA transaction processes. However, in thermophiles, a different enzyme maintains the genome in a positively supercoiled form to protect from denaturation by excessive heat. These varied functions are carried out by different topoisomerases. Therefore, each organism maintains a minimum required set of the enzymes and the absence of a certain enzyme may be compensated for by topoisomerases with dual functions. For example, Mycobacterium tuberculosis and many other slow growing mycobacteria do not possess topoisomerase IV or its homologs. In these organisms, the DNA gyrase is suggested to carry out both negative supercoiling and decatenation reactions. Therefore, the mycobacterial DNA gyrase must be able to manage between both the functions in vivo. In contrast, Mycobacterium smegmatis and few other mycobacteria contain an additional type II topoisomerase which does not resemble any known type II enzyme but could catalyze relaxation and decatenation reactions. Importantly, the enzyme displays a unique ability to introduce limited positive supercoils and may have certain functions inside the cell which remains to be studied. Owing to the indispensability for bacterial survival topoisomerases present themselves as important drug targets. A large number of inhibitors have been found to inhibit the enzyme and thereby killing the bacterial. Among these, quinolones are successfully being used as broad spectrum antibacterial drugs. Although the commonly used quinolones inhibit many bacterial pathogens, a reduced susceptibility is exhibited by some of the pathogens e.g. Mycobacterium tuberculosis. To circumvent the lower efficacy of existing drugs, new and modified quinolones have been developed which are highly effective against mycobacteria. The difference in the susceptibility may be conferred by a difference in the chemical property of the drug and the interacting residues present in the enzyme. In the present thesis efforts have been made to understand the mechanism of the type II topoisomerases from mycobacteria and drug action on these enzymes. The thesis is divided into four chapters. In Chapter I of the thesis an introduction is provided on the topoisomerases, their classification and different reactions catalyzed by these enzymes. As the work in present thesis has been carried out with type II topoisomerases, introduction of type II enzymes, their structure and mechanisms is elaborated. DNA gyrase, its mechanism of reaction and in vitro and in vivo functions are explained in great detail. DNA gyrase and topoisomerase IV are targeted by a range of different inhibitors. These different classes of inhibitors and their mechanism of action are described. Finally, the mechanism of mycobacterial DNA gyrase with structural information and the current understanding of quinolone action on the enzyme are explained. The chapter ends with the objective of the study in the present thesis. In chapter II, the studies are aimed at understanding the molecular basis for decatenation carried out by mycobacterial DNA gyrase. Previous work from the laboratory showed that the enzyme can carry out decatenation more efficiently than its homolog from E. coli. It was shown that the mycobacterial enzyme binds two DNA molecules in trans in a length dependent manner. The ability to bind the second DNA is conferred upon the holoenzyme by ATPase subunit (GyrB) subunit which alone can bind DNA. Similar studies using topo IV from E. coli, the strongest known decatenase showed binding of two DNA molecules and the second DNA binding by ATPase (ParE) subunit. However, GyrB subunit from E. coli DNA gyrase, a weaker decatenase, does not bind second DNA molecule efficiently. The results provide a general mechanism for decatenation by type II enzymes in which efficient binding of second DNA is important. In Chapter III, studies have been carried out using topo NM, an atypical type II topoisomerase from Mycobacterium smegmatis. The enzyme has been characterized previously in the laboratory. In addition to efficient decatenation and relaxation, the enzyme exhibits a unique ability to introduce positive supercoils into the DNA. As demonstrated for the mycobacterial DNA gyrase and topo IV in the Chapter II, the ATPase subunit (Topo N) of topo NM, binds second DNA efficiently. The binding of both gate and transport segments increases with the length of the DNA. Binding of two DNA molecules by the holoenzyme appears to be a cumulative effect of DNA binding to individual subunits. In the absence of any inhibitor, the enzyme accumulates cleaved DNA products with shorter DNA but not with larger DNA. The cleavage of the shorter DNA is supported only in the presence of Mg2+ and Mn2+. Another important property of the enzyme is to introduce positive supercoils which appears to be due to its efficient utilization of ATP and a high rate of reaction. Chapter IV deals with the interaction of mycobacterial gyrase with fluoroquinolones (FQs). Although DNA gyrase is the sole target of the FQs in M. tuberculosis, the lower susceptibility to commonly used FQs have led to the studies to find out more effective quinolones. Previous studies from the laboratory showed a lower susceptibility of the mycobacterial gyrase to ciprofloxacin, but moxifloxacin could inhibit the enzyme efficiently. The better inhibition by moxifloxacin appears to be due to efficient trapping of the enzyme-DNA covalent complex. Both ciprofloxacin and moxifloxacin bind the DNA gyrase from mycobacteria, E. coli and E. coli topo IV, independent of DNA. The extent of binding also correlates with the inhibition potential of the drug against a given enzyme. A general model of quinolone enzyme interaction is provided wherein the quinolones are shown to interact with GyrA subunit or holoenzyme or the enzyme- DNA complex which would finally result in the trapping of the covalent complex.

Topoisomerases são enzimas nucleares que participam na regulação da estrutura do DNA nas células eucarióticas. A topoisomerase III é o mais novo membro da família das topoisomerases. Seu papel no desenvolvimento dos tumores mamários ainda necessita ser investigado. O objetivo do presente estudo foi avaliar a imunoexpressão da topoisomerase III nos carcinomas mamários, e comparar sua expressão com dados clinicopatológicos e marcadores imunohistoquímicos clássicos de importância prognóstica nos carcinomas mamários. Utilizando-se tissue microarrays contendo 171 casos de carcinomas ductais mamários primários, foi analisada a expressão imunohistoquímica de topoisomerase III, receptor de estrógeno, receptor de progesterona, HER-2, Ki67, p53 e BRCA-1. Positividade para topoisomerase III foi encontrada em 33,9% dos casos, e sua expressão relacionou-se com metástases à distância (p=0.036) e óbito (p=0.006). Negatividade para topoisomerase III relacionou-se com negatividade para HER=2 (p<0.001), p53 (p<0.001) e BRCA-1 (p=0.001), e com baixa expressão de Ki-67 (p<0.001). Na Análise de Riscos Múltiplos de Cox, a expressão de topoisomerase III foi um significante preditor de sobrevida [razão de risco 3.006 (intervalo de confiança a 95%: 1.582-5.715); p=0.001]. Concluindo, a topoisomerase III pode ser útil na avaliação do prognóstico de pacientes com câncer de mama, além de ser um fator independente de predição da sobrevida. / Topoisomerases are ubiquitous nuclear enzymes that regulate DNA structure in eukaryotic cells. The role of topoisomerase III, the newest member of the topoisomerase family, in the clinical outcome of breast cancer is still poorly understood. This study aims to investigate the immunoexpression of topoisomerase III in breast cancer and its relationships with clinicopathological features and immunohistochemical markers of prognostic significance in breast pathology. Using tissue microarrays containing 171 cases of primary invasive breast cancer, we analyzed the immunoexpression of topoisomerase III, estrogen receptor, progesterone receptor, HER-2, Ki67, p53 and BRCA-1. Immunostaining for topoisomerase III was found in 33.9% of breast carcinomas, and immunopositivity was related with distant metastasis (p=0.036) and death (p=0.006). Decreased expression of topoisomerase III was related with negativity with HER-2 (p<0.001), p53 (p<0.001) and BRCA1 (p=0.001) and low expression of Ki67 (p<0.001). In the multivariate analysis, topoisomerase III expression was a significant predictor of survival [hazard ratio 3.006 (95% confidence interval 1.582-5.715); p=0.001]. In conclusion, topoisomerase III expression can be a useful marker in assessing the prognosis of patients with breast cancer and is an independent predictor of survival.

Topoisomerases são enzimas nucleares que participam na regulação da estrutura do DNA nas células eucarióticas. A topoisomerase III é o mais novo membro da família das topoisomerases. Seu papel no desenvolvimento dos tumores mamários ainda necessita ser investigado. O objetivo do presente estudo foi avaliar a imunoexpressão da topoisomerase III nos carcinomas mamários, e comparar sua expressão com dados clinicopatológicos e marcadores imunohistoquímicos clássicos de importância prognóstica nos carcinomas mamários. Utilizando-se tissue microarrays contendo 171 casos de carcinomas ductais mamários primários, foi analisada a expressão imunohistoquímica de topoisomerase III, receptor de estrógeno, receptor de progesterona, HER-2, Ki67, p53 e BRCA-1. Positividade para topoisomerase III foi encontrada em 33,9% dos casos, e sua expressão relacionou-se com metástases à distância (p=0.036) e óbito (p=0.006). Negatividade para topoisomerase III relacionou-se com negatividade para HER=2 (p<0.001), p53 (p<0.001) e BRCA-1 (p=0.001), e com baixa expressão de Ki-67 (p<0.001). Na Análise de Riscos Múltiplos de Cox, a expressão de topoisomerase III foi um significante preditor de sobrevida [razão de risco 3.006 (intervalo de confiança a 95%: 1.582-5.715); p=0.001]. Concluindo, a topoisomerase III pode ser útil na avaliação do prognóstico de pacientes com câncer de mama, além de ser um fator independente de predição da sobrevida. / Topoisomerases are ubiquitous nuclear enzymes that regulate DNA structure in eukaryotic cells. The role of topoisomerase III, the newest member of the topoisomerase family, in the clinical outcome of breast cancer is still poorly understood. This study aims to investigate the immunoexpression of topoisomerase III in breast cancer and its relationships with clinicopathological features and immunohistochemical markers of prognostic significance in breast pathology. Using tissue microarrays containing 171 cases of primary invasive breast cancer, we analyzed the immunoexpression of topoisomerase III, estrogen receptor, progesterone receptor, HER-2, Ki67, p53 and BRCA-1. Immunostaining for topoisomerase III was found in 33.9% of breast carcinomas, and immunopositivity was related with distant metastasis (p=0.036) and death (p=0.006). Decreased expression of topoisomerase III was related with negativity with HER-2 (p<0.001), p53 (p<0.001) and BRCA1 (p=0.001) and low expression of Ki67 (p<0.001). In the multivariate analysis, topoisomerase III expression was a significant predictor of survival [hazard ratio 3.006 (95% confidence interval 1.582-5.715); p=0.001]. In conclusion, topoisomerase III expression can be a useful marker in assessing the prognosis of patients with breast cancer and is an independent predictor of survival.

Fluoroquinolones, broad-spectrum bactericidal antibiotics, exert their effects by inhibiting type II topoisomerases through the formation of a fluoroquinolone-DNA-topoisomerase ternary complex. Recently, newer, structurally unique fluoroquinolones have been shown to kill bacteria by promoting chromosomal fragmentation in the presence and absence of protein synthesis, thus allowing fluoroquinolones to potentially be used in the treatment of microorganisms that go into a dormant state. There is a need to further understand the structure activity relationships (SAR) of fluoroquinolones to develop new antibiotics that can kill dormant bacteria and are active against current resistant strains. The hypothesis that structurally unique fluoroquinolones interact with the DNA- fluoroquinolone-topoisomerase ternary complex in a unique way that leads to different killing pathways is the basis of this work. The first approach to understand SAR for fluoroquinolones to kill non-growing bacteria was to evaluate the effect of modifications at the C-8 and C-5 positions on lethality. Novel, synthetically-derived and commercially-available fluoroquinolones were evaluated for ability to kill Escherichia coli in the presence and absence of chloramphenicol, a known protein synthesis inhibitor used to simulate non-growing bacteria. The second study was to understand SAR of fluoroquinolone-class agents necessary to maintain antibacterial activity against common fluoroquinolone resistance-causing bacterial mutations on topoisomerase IV. A panel of novel fluoroquinolones, 2,4-quinazoline diones, and fluoroquinolone-like analogues with unique substitution combinations at C-8 and C-7 was synthesized and evaluated for ability to poison wild-type and mutant Bacillus anthracis topoisomerase IV. The third study to understand the contribution of SAR of fluoroquinolone-class agents to novel killing mechanisms was to evaluate the binding interaction of fluoroquinolones to double-stranded and nicked DNA. Binding affinities of fluoroquinolones to DNA were determined; fluoroquinolones were found to bind different DNA types with varied affinities. The ability of a series of C-8 and C-7 modified fluoroquinolones to stabilize or destabilize DNA was assessed. The results of these studies also add broadly to the understanding of SAR associated with fluoroquinolone-class antibiotics for killing in the presence and absence of protein synthesis, maintaining activity in the presence of resistance-causing mutations in the target enzymes, and increasing binding interactions with different types of DNA.

La mitochondrie est une organelle essentielle possédant son propre ADN circulaire. Cet ADN peut présenter des mutations et/ou des délétions, consécutives à l’exposition à différents types de dommages ou en raison de protéines mutées. Ces mutations ou délétions sont impliquées dans de nombreuses pathologies, dont les cancers, et le vieillissement. Leur apparition peut survenir notamment lors de la réplication ou de la réparation. A ce jour, la réplication et la réparation mitochondriales ne sont pas encore bien élucidées. L’objectif de ce projet est donc de mieux en appréhender les mécanismes et de mieux comprendre l’émergence d’anomalies en nous intéressant plus particulièrement à une délétion appelée « Common Deletion ». Ce travail reposait sur l’hypothèse que cette délétion put résulter d’une mauvaise réparation de cassure(s) double-brin et/ou d’une erreur durant la réplication de l’ADN mitochondrial. L’analyse de ces résultats révèle que la formation de la « Common Deletion » ne nécessite qu’une seule cassure double-brin proche des séquences répétées entourant cette dernière et implique les protéines de la réplication de l’ADN mitochondrial. Ainsi, ce travail permet de mieux saisir les mécanismes de réplication et de réparation assurant la stabilité de l’ADN mitochondrial. Un second projet a été de proposer un modèle d’étude in vitro des topoisomérases en utilisant des minicercles d’ADN permettant la visualisation du complexe covalent, étape clef de la réaction de relaxation de ces enzymes. / Mitochondria is an essential organelle with its own circular DNA. This DNA may exhibit mutations and/or deletions, as a result of exposure to different types of damage or due to mutated proteins. These mutations or deletions are involved in many pathologies, including cancers, and aging. They may occur during replication or repair. For now, mitochondrial replication and repair have not yet been fully elucidated. The objective of this project is therefore to better understand the mechanisms and the emergence of anomalies by focusing on a deletion called "Common Deletion". This work was based on the assumption that this deletion could result from poor repair of double-strand break(s) and/or error during mitochondrial DNA replication. Analysis of these results reveals that the formation of the "Common Deletion" requires only a single double-strand break close to the repeated sequences surrounding the latter and involves the proteins of mitochondrial DNA replication. Thus, this work makes it possible to better understand the mechanisms of replication and repair ensuring the stability of mitochondrial DNA. A second project was to propose an in vitro model for topoisomerases using DNA minicircles allowing visualization of the covalent complex, a key step in the relaxation reaction of these enzymes.