Breast cancer is one of the most prevalent cancers affecting women worldwide. In the breast, estrogen receptor alpha (ERα), upon binding with ligands, activates gene transcription and promotes cell growth and proliferation. Tamoxifen, a selective antagonist of ERα in breast, has been proved to be effective therapeutically. In spite of this, resistance remains a prominent issue and underlying mechanisms are not yet fully understood. Aberrant regulation of ER expression at genetic and transcriptional levels has been implicated as the mechanisms accounting for tamoxifen resistance. However, regulation of ERα expression at translational level including protein synthesis and degradation has not yet been characterized and its relevance to tamoxifen resistance has not been described. At level of protein synthesis, eukaryotic translation initiation factor 4E (eIF4E) selectively enhances the translation of 4E-sensitive mRNAs which contain long and complex 5’-untraslated regions (5’-UTR). eIF4E is often over-expressed in cancers. In silico analysis revealed that ERα contained a highly structured 5’-UTR similar to reported eIF4E-sensitive mRNAs, suggesting that ERα mRNA might be eIF4Esensitive. We showed by polysome fractionation and subsequent Q-PCR quantification that the ERα mRNAs were more actively translated in the cell line expressing higher levels of eIF4E. Consistently, transient transfection of eIF4E into an ERα-positive cell line resulted in enhanced protein expression of ERα. Moreover, subcelluar fractionation showed that eIF4E was bound with ERα mRNAs in the nucleus thus participating in transportation of mRNAs from the nucleus into the cytoplasm. Therefore, eIF4E could positively modulate protein synthesis of ERα by enhancing mRNA export in the nucleus as well as translation in the cytoplasm. Their positive correlation was validated in vivo using 106 Chinese breast cancer samples (Chi-square test, p=0.004). It was also found that elevated expression of eIF4E could mediate resistance to tamoxifen treatment and enhance cell survival. This could be due to enhanced expression of ERα or activation of PI3K/Akt pathway upon eIF4E over-expression. At the level of degradation, ERα is conjugated to poly-ubiquitin chains catalyzed by multiple enzymes and degraded by 26S polysomes. Carboxyl-terminus of Hsc70- interacting protein (CHIP) is an E3 enzyme specific for ERα degradation through interaction with ERα’s ligand-binding domain (LBD). Various splicing variants of ERα have been reported and implicated in tamoxifen resistance by interfering with functions of ERα wild type. Variants ERαΔ4, ERαΔ5, ERαΔ6/7 and ERαΔ7 with different degrees of truncation in their LBDs and differential expression were detected or reported in human breast cancers. Their interactions with CHIP may be different, resulting in variations in degradation. We found that the degradation of ERαΔ6/7 through ubiquitin-proteasome pathway was impaired whilst the degradation of other variants were less affected. This finding suggests that the binding site of CHIP to ERαmight be located within the peptide sequences encoded by exon6. Furthermore, as ERαΔ6/7 plays a dominant negative role in regulating functions of ERα wild type, aborted degradation of this variant may result in accumulation of this variant in the cell, inhibiting and inactivating ERα, making the cells refractile to tamoxifen treatment. / published_or_final_version / Pathology / Master / Master of Philosophy

Tamoxifen and aromatase inhibitors are treatment options for women with breast cancer and evidence on the risk of stroke is important in choosing between these two options. A systematic review of two randomized controlled trials and their nine related trial reports showed different methods for adverse event reporting and inconsistent estimates of stroke risk. In an observational cohort study of 5443 Ontario women, aged 66 years or older with early stage breast cancer, 86 ischemic stroke events (1.6%) occurred during follow-up of 5 years. There was no statistically significant difference in the risk of stroke between the hormone therapy groups [adjusted HR for tamoxifen compared to AI 1.330 (0.810, 2.179)]. Results were similar across cardiovascular disease risk groups and were robust to different follow up periods and analytic methods. This study suggests that there is no significant difference in stroke between these treatment options.

Tamoxifen and aromatase inhibitors are treatment options for women with breast cancer and evidence on the risk of stroke is important in choosing between these two options. A systematic review of two randomized controlled trials and their nine related trial reports showed different methods for adverse event reporting and inconsistent estimates of stroke risk. In an observational cohort study of 5443 Ontario women, aged 66 years or older with early stage breast cancer, 86 ischemic stroke events (1.6%) occurred during follow-up of 5 years. There was no statistically significant difference in the risk of stroke between the hormone therapy groups [adjusted HR for tamoxifen compared to AI 1.330 (0.810, 2.179)]. Results were similar across cardiovascular disease risk groups and were robust to different follow up periods and analytic methods. This study suggests that there is no significant difference in stroke between these treatment options.

Diss. Linköping : Linköpings universitet, 2007.

Introdução: As variações da CYP2D6 estão associadas com o desfecho clínico das pacientes na terapia adjuvante do câncer de mama com tamoxifeno (TAM). Esta associação deve-se principalmente a hidroxilação do N-desmetiltamoxifeno (NDT) pela CYP2D6 a endoxifeno (EDF) que, por sua alta potência antiestrogênica, é o principal responsável pela eficácia terapêutica. O objetivo deste estudo foi avaliar a relação entre o genótipo e o fenótipo da CYP2D6 com os níveis de EDF e a razão metabólica [NDT]/[EDF] em uma população do Sul do Brasil. Métodos: Foram obtidas amostras de plasma em vale de 97 pacientes em terapia com o tamoxifeno. A genotipagem da CYP2D6 foi realizada com ensaio Luminex, com determinação de escores de atividade genotípica (EAG). As concentrações do TAM e seus metabólitos foram determinados por CLAE-DAD e classificadas em metabolizadores lentos (ML), intermediários (MI), rápidos com atividade diminuída (MR-D), rápidos com atividade rápida (MR-R) e ultra-rápidos (UR). A fenotipagem foi realizada através da determinação do dextrometorfano (DMT) e do dextrorfano (DTF) por CLAE-FL nas amostras de plasma coletadas três horas após administração oral de 33 mg de DMT. A atividade da CYP2D6 foi avaliada pela razão metabólica [DMT]/[DTF]. Resultados: A genotipagem da CYP2D6 mostrou prevalência de 4,1% de ML, 4,1% de MI, 49,5% de MR-D, 39,2% de MR-R e 3,1% de UR. O genótipo (EAG) foi significativamente correlacionado com o fenótipo ([DMT]/[DTF]), com uma associação moderada (rs= -0,463; p<0,001). As medianas das concentrações plasmáticas do TAM e seus metabólitos (ng mL-1) foram: TAM 57,17; HTF 1,01; EDF 6,21; NDT 125,50. Os níveis de EDF foram inferiores nos ML em comparação aos MR (p<0,05). O fenótipo apresentou maior associação, porém ainda moderada, com os níveis de EDF e [NDT]/[EDF] em comparação ao genótipo (r= -0,507 r=0,625, p<0,001 versus r= 0,356 r=0,516; p<0,01). Ao fenótipo da CYP2D6 foram atribuídas 26% da variabilidade dos níveis de EDF e 38 % das razões metabólicas [NDT]/[EDF], enquanto que ao genótipo foram atribuídas 12% e 27 %, respectivamente. Conclusão: A genotipagem e/ou fenotipagem da CYP2D6 não foram capazes de predizer completamente as concentrações de EDF. Desta forma, sugerimos que estudos futuros utilizem o monitoramento dos níveis de EDF durante a terapia com TAM, com o objetivo de avaliar a sua efetividade. / Background: An association between CYP2D6 variation and clinical outcomes among women with breast cancer treated with tamoxifen (TAM) has been demonstrated, such that the presence of 2 functional CYP2D6 alleles was associated with better clinical outcomes. This association is mainly due the CYP2D6 mediated hydroxylation of N-desmethyltamoxifen (NDT) to yield endoxifen (EDF), which because of its high antiestrogenic potency, is the main responsible for the therapeutic efficacy of TAM. The aim of this study was to evaluate the relation of CYP2D6 genotyping and phenotyping with EDF levels and [NDT]/[EDF] metabolic ratio in breast cancer patients from South of Brazil under TAM therapy. Methods: Trough blood samples were collected from 97 patients. CYP2D6 genotyping was performed with a Luminex assay and calculation of Genotypic activity scores (GAS). Tamoxifen and metabolites EDF, NDT and 4-hidroxy-tamoxifen (HTF) were measured in plasma by HPLC-PDA. CYP2D6 phenotyping was performed by determination of dextromethorphan (DMT) and dextrorphan (DTF) by HPLC-FL at plasma collected three hours after oral administration of 33 mg of DMF. Phenotypes were given according to [DMT]/[DTF] metabolic ratio. Results: CYP2D6 genotyping indicated a prevalence of 4.1% PM, 4.1% IM, 49.5% EM-S, 39.2% EM-F and 3.1% UM. Genotype (GAS), was significantly correlated with phenotype ([DMT]/[DTF]), with a moderate association (rs= -0.463; p<0.001). Median plasma concentrations (ng mL-1) (N=97) were: TAM 57.17; HTF 1.01; EDF 6.21; NDT 125.50. EDF levels were lower in PM than in EM (p<0.05). Phenotype showed stronger, but still moderate, association with EDF and [NDT]/[EDF] than genotype (r= -0.507 r=0.625, p<0.001 versus r= 0,356 r=0.516, p<0.01). Phenotype accounted for 26% of the variability in EDF levels and 38 % of [NDT]/[EDF], while genotype for 12% and 27 %, respectively. Conclusion: CYP2D6 genotyping and/or phenotyping could not fully predict EDF concentrations. Monitoring EDF itself could be considered in further studies during TAM therapy in order to evaluate its efficacy

Made available in DSpace on 2015-07-22T20:50:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-11-25. Added 1 bitstream(s) on 2015-08-11T03:25:59Z : No. of bitstreams: 1 Publico-11912.pdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Introdução: A endocrinoterapia é uma das principais responsáveis pela redução de mortalidade do câncer de mama. Biomarcadores preditivos de resposta celular precoce vêm sendo estudados com intuito de prever precocemente a hormonioresistência. Freqüentes deleções e mutações têm sido descritas no gene p16 em diversos tipos de tumores, mas pouco se sabe sobre seu papel no câncer de mama e seu comportamento após endocrinoterapia neoadjuvante com tamoxifeno e anastrozol. Objetivos: Estudar a expressão do p16 e dos receptores de estrogênio e progesterona (RE e RP) em pacientes na pós - menopausa com carcinoma de mama RE e/ ou RP (+) após curto período (26 dias) de tratamento com tamoxifeno, anastrozol e placebo. Métodos: Estudo prospectivo randomizado duplo-cego realizado com 58 pacientes dos Hospitais Pérola Byington e São Paulo da UNIFESP (São Paulo - Brasil) com carcinoma ductal infiltrativo de mama, nos estádios II e III, que no período pré-operatório foram subdivididas em três grupos: P (placebo, N=25), T (tamoxifeno 20mg/dia, N=15) e A (anastrozol 1mg/dia, N=18). A biópsia foi realizada no momento do diagnóstico e após a cirurgia definitiva (26º dia) e os tumores foram isolados por micro-arranjos teciduais. O estudo imunoistoquímico foi realizado com anticorpos para p16 (Dako- OA315), RE (Neomarkers-M7047), RP (Dako- M3569). Realizou-se o estudo semiquantitativo utilizando-se os critérios de Allred e o estudo estatístico pelo teste paramétrico de Anova. Resultados: A positividade do p16 variou de 22 para 17%, respectivamente pré e pós tratamento com anastrozol; de 8 para 4% no grupo placebo e não houve variação, com 7% de positividade, no grupo que recebeu tamoxifeno. A comparação entre grupos e tempos não apresentou relação significativa para o p16 (p=0,17). Não foi encontrada correlação entre a positividade do p16 e o status hormonal (RE e RP). Conclusão: Não houve diferença estatística significante entre os três grupos estudados. Futuros estudos com métodos moleculares poderão esclarecer dúvidas suscitadas a respeito do tempo de exposição à droga necessária para interferir nos biomarcadores e proteínas. / Background: Frequent deletions or mutations of the INK4 gene, which encodes the cyclin-dependent kinase 4 inhibitor p16INK4a, have been documented in various human cancers, but little is known about the role of this tumor suppressor gene in primary breast cancer and there is a lack in the literature about its expression behavior in neoadjuvant endocrinetherapy with tamoxifen or anastrozole. Objective: Analysis of p16INK4a expression in patients with invasive ductal carcinomas (IDC) prior to tamoxifen and anastrozole neoadjuvant treatment and possible correlation between predictive and prognostical factors – estrogen receptor (ER), progesterone receptor (PgR). Methods: We examined p16INK4a mRNA expression and its relationship with short period (26 days) neoadjuvant endocrine therapy with tamoxifen and anastrozole in 58 primary breast cancers with palpable ER-positive IDC. They were double-blind randomized in three neoadjuvant treatment groups for 21 days: Anastrozole 1mg/day (n= 17), Placebo (n=25) and Tamoxifen 20mg/day (n=15). Biomarkers status (ER, PgR and p16) were obtained by comparing single immunohistochemical evaluation of pre and post-surgery samples using Allred’s method. Statistical analyses were performed using the SPSS software for Windows. Results: Variation in p16 was 22% to 17% in anastrozole group, 8% to 4% in placebo group and there was no variation in tamoxifen group, standing in 7%. There was no significant statistical diference in p16INK4a expression among the three groups (p=0.17). Variation in p16 was 12% to 9% (p<0.05) when considering the three groups together. There was a significant decrease of p16 expression in pre and post surgery results. There was no significant statistical correlation between p16 expression and hormonal status (RE and RP). Conclusions: There was no significant statistical diference in p16INK4a expression among the three groups. There was a significant statistical decrease in p16INK4a expression when compared pre and post surgery values. These findings could indicate that expression of p16 and variation in pre and post surgery samples are associated with hormone responsiveness and mechanisms of resistance. There were no significant statistical correlation between p16 expression and hormonal status (RE and RP). Further studies are necessary to understand their functional interrelationships and whether high p16INK4a expression may be associated with a lack of hormone responsiveness in breast cancer. / TEDE / BV UNIFESP: Teses e dissertações

Made available in DSpace on 2014-12-17T14:13:20Z (GMT). No. of bitstreams: 1 CarlosANJ.pdf: 292862 bytes, checksum: 36f729a3d08d7c1e5c99393f43d9acef (MD5) Previous issue date: 2007-10-19 / Tamoxifen (TX), a drug used in the treatment of breast cancer, may cause hepatic changes in some patients. The consequences of its use on the liver tissues of rats with or without diabetes mellitus (DM) have not been fully explored. The purpose of this multidisciplinary study was to evaluate the correlation between plasma hepatic enzyme levels and the presence of iron overload in the hepatic tissue of female Wistar rats with or without streptozotocin-induced DM and using TX. Female rats were studied in control groups: C-0 (non-drug users), C-V (sorbitol vehicle only) and C-TX (using TX). DM (diabetic non-drug users) and DM-TX (diabetics using TX) were the test groups. Sixty days after induced DM, blood samples were collected for glucose, alanine aminotransferase (ALT), aspartate aminotransferase (AST) alkaline phosphatase (ALP) and bilirubin measures. Hepatic fragments were processed and stained with hematoxylin and eosin (H&E), Masson s trichrome, Perls. The hepatic iron content was quantified by atomic absorption spectrometry. AST, ALT and ALP levels were significantly elevated in the DM and DM-TX groups, with unchanged bilirubin levels. Liver iron overload using Perls stain and atomic absorption spectrometry were observed exclusively in groups C-TX and DM-TX. There was positive correlation between AST, ALT and ALP levels and microscopic hepatic siderosis intensity in group DM-TX. In conclusion, TX administration is associated with liver siderosis in diabetic and non-diabetic rats. In addition, TX induced liver iron overload with unaltered hepatic function in 2 non-diabetic rats and may be a useful tool for investigating the biological control of iron metabolism / O tamoxifeno? (TX), utilizado no tratamento do c?ncer de mama, pode causar altera??es hep?ticas. As conseq??ncias de seu uso em tecido hep?tico de ratos com ou sem diabetes mellitus (DM) n?o foram completamente investigadas. O estudo de car?ter multidisciplinar visou avaliar a correla??o entre n?veis de enzimas hep?ticas no plasma e a presen?a de sobrecarga de ferro em tecido hep?tico de ratas com ou sem DM induzido por estreptozotocina e em uso de TX. Ratas Wistar foram estudadas em grupos? controle: C-O (sem uso de droga), C-V (somente sorbitol) e C-TX (em uso de TX). DM (diab?ticos sem uso de droga) e DM-TX (diab?ticos em uso de TX) foram os grupos teste. Sessenta dias ap?s a indu??o do DM, amostras de sangue foram colhidas para a mensura??o de glicose, alanina aminotransferase (ALT), aspartato aminotransferase (AST) , fosfatase alcalina (ALP) e bilirrubina. Amostras hep?ticas foram coradas com hematoxilina e eosina, Tricr?mio de Masson e Perls. O conte?do hep?tico de ferro foi quantificado por espectrometria de absor??o at?mica. AST, ALT e ALP apresentaram-se significativamente elevados nos grupos DM e DM-TX, com bilirrubina n?o alterada. Siderose ? colora??o Perls e pela espectrometria de absor??o at?mica foram observados apenas nos grupos C-TX e DM-TX. Houve correla??o positiva entre os n?veis de AST, ALT e ALP e a intensidade da siderose hep?tica microsc?pica no grupo DM-TX. Em conclus?o, o uso de TX ? associada com siderose hep?tica em ratas diab?ticas ou n?o. O TX induziu sobrecarga hep?tica de ferro sem alterar a fun??o hep?tica em animais n?o diab?ticos e pode ser uma ferramenta ?til no estudo do metabolismo do ferro.A participa??o de pesquisadores em Patologia, Cirurgia Experimental, Farm?cia Cl?nica, Toxicologia, Nutri??o, Mastologia, Endocrinologia e Biologia Molecular do Centro de Ci?ncias da Sa?de (CCS) e o Departamento de Estat?stica do Centro de Ci?ncias Exatas e da Terra (CCET), de forma integrada e coordenada, foi fundamental para a execu??o do projeto proposto, de car?ter multidisciplinar

Introdução: As variações da CYP2D6 estão associadas com o desfecho clínico das pacientes na terapia adjuvante do câncer de mama com tamoxifeno (TAM). Esta associação deve-se principalmente a hidroxilação do N-desmetiltamoxifeno (NDT) pela CYP2D6 a endoxifeno (EDF) que, por sua alta potência antiestrogênica, é o principal responsável pela eficácia terapêutica. O objetivo deste estudo foi avaliar a relação entre o genótipo e o fenótipo da CYP2D6 com os níveis de EDF e a razão metabólica [NDT]/[EDF] em uma população do Sul do Brasil. Métodos: Foram obtidas amostras de plasma em vale de 97 pacientes em terapia com o tamoxifeno. A genotipagem da CYP2D6 foi realizada com ensaio Luminex, com determinação de escores de atividade genotípica (EAG). As concentrações do TAM e seus metabólitos foram determinados por CLAE-DAD e classificadas em metabolizadores lentos (ML), intermediários (MI), rápidos com atividade diminuída (MR-D), rápidos com atividade rápida (MR-R) e ultra-rápidos (UR). A fenotipagem foi realizada através da determinação do dextrometorfano (DMT) e do dextrorfano (DTF) por CLAE-FL nas amostras de plasma coletadas três horas após administração oral de 33 mg de DMT. A atividade da CYP2D6 foi avaliada pela razão metabólica [DMT]/[DTF]. Resultados: A genotipagem da CYP2D6 mostrou prevalência de 4,1% de ML, 4,1% de MI, 49,5% de MR-D, 39,2% de MR-R e 3,1% de UR. O genótipo (EAG) foi significativamente correlacionado com o fenótipo ([DMT]/[DTF]), com uma associação moderada (rs= -0,463; p<0,001). As medianas das concentrações plasmáticas do TAM e seus metabólitos (ng mL-1) foram: TAM 57,17; HTF 1,01; EDF 6,21; NDT 125,50. Os níveis de EDF foram inferiores nos ML em comparação aos MR (p<0,05). O fenótipo apresentou maior associação, porém ainda moderada, com os níveis de EDF e [NDT]/[EDF] em comparação ao genótipo (r= -0,507 r=0,625, p<0,001 versus r= 0,356 r=0,516; p<0,01). Ao fenótipo da CYP2D6 foram atribuídas 26% da variabilidade dos níveis de EDF e 38 % das razões metabólicas [NDT]/[EDF], enquanto que ao genótipo foram atribuídas 12% e 27 %, respectivamente. Conclusão: A genotipagem e/ou fenotipagem da CYP2D6 não foram capazes de predizer completamente as concentrações de EDF. Desta forma, sugerimos que estudos futuros utilizem o monitoramento dos níveis de EDF durante a terapia com TAM, com o objetivo de avaliar a sua efetividade. / Background: An association between CYP2D6 variation and clinical outcomes among women with breast cancer treated with tamoxifen (TAM) has been demonstrated, such that the presence of 2 functional CYP2D6 alleles was associated with better clinical outcomes. This association is mainly due the CYP2D6 mediated hydroxylation of N-desmethyltamoxifen (NDT) to yield endoxifen (EDF), which because of its high antiestrogenic potency, is the main responsible for the therapeutic efficacy of TAM. The aim of this study was to evaluate the relation of CYP2D6 genotyping and phenotyping with EDF levels and [NDT]/[EDF] metabolic ratio in breast cancer patients from South of Brazil under TAM therapy. Methods: Trough blood samples were collected from 97 patients. CYP2D6 genotyping was performed with a Luminex assay and calculation of Genotypic activity scores (GAS). Tamoxifen and metabolites EDF, NDT and 4-hidroxy-tamoxifen (HTF) were measured in plasma by HPLC-PDA. CYP2D6 phenotyping was performed by determination of dextromethorphan (DMT) and dextrorphan (DTF) by HPLC-FL at plasma collected three hours after oral administration of 33 mg of DMF. Phenotypes were given according to [DMT]/[DTF] metabolic ratio. Results: CYP2D6 genotyping indicated a prevalence of 4.1% PM, 4.1% IM, 49.5% EM-S, 39.2% EM-F and 3.1% UM. Genotype (GAS), was significantly correlated with phenotype ([DMT]/[DTF]), with a moderate association (rs= -0.463; p<0.001). Median plasma concentrations (ng mL-1) (N=97) were: TAM 57.17; HTF 1.01; EDF 6.21; NDT 125.50. EDF levels were lower in PM than in EM (p<0.05). Phenotype showed stronger, but still moderate, association with EDF and [NDT]/[EDF] than genotype (r= -0.507 r=0.625, p<0.001 versus r= 0,356 r=0.516, p<0.01). Phenotype accounted for 26% of the variability in EDF levels and 38 % of [NDT]/[EDF], while genotype for 12% and 27 %, respectively. Conclusion: CYP2D6 genotyping and/or phenotyping could not fully predict EDF concentrations. Monitoring EDF itself could be considered in further studies during TAM therapy in order to evaluate its efficacy

A enzima indoleamina 2,3 dioxigenase - IDO desempenha um importante papel na regulação do sistema imunológico, impedindo o estabelecimento de uma resposta imunológica no microambiente em que é expressa. Quando ativada, é responsável por catabolizar o aminoácido triptofano, privando células em proliferação deste componente e gerando metabólitos que as induzem a apoptose. Hormônios, como o estrógeno e a progesterona são capazes de alterar as funções imunológicas nas células, podendo levar à alteração na expressão da IDO, contudo, os mecanismos responsáveis por este efeito, ainda não são claros. Sabe-se que diversas células tumorais e leucócitos adjacentes à região do tumor podem expressar IDO e são sensíveis à ação desses hormônios. Os carcinomas mamários são os mais comuns nos cães, apresentando grande expressão de IDO. Em face destas informações, este trabalho buscou investigar a influência do estrógeno e da progesterona na expressão da IDO em cultura de células provenientes do carcinoma mamário de cadelas tratadas com os referidos hormônios e seus respectivos antagonistas de receptor (tamoxifeno estrógeno e mifepristone progesterona). A expressão da enzima foi analisada pela imuno-histoquímica, citometria de fluxo e quantificada pela técnica de western blot, enquanto os mRNA foram analisados por Real time-PCR. Os resultados da quantificação da enzima (citometria de fluxo e Western blot) seguiram o mesmo padrão da expressão de mRNA. Perante a suplementação das células com estrógeno, houve a elevação da expressão da enzima e do respectivo mRNA que, após a adição de tamoxifeno, antagonista do receptor do estrógeno, reduziu a referida expressão. A suplementação com progesterona, resultou numa discreta diminuição na expressão da IDO e respectivo mRNA, a qual foi revertida após a adição do inibidor de progesterona (mifepristone). Com estes achados, conclui-se que os hormônios esteroides, devido às modificações nos padrões de citocinas expressas pelas células PR e ER positivas no microambiente tumoral, provocam alterações na expressão de IDO. / The indoleamine 2,3 dioxygenase - IDO enzyme plays an important role in the regulation of the immune system, preventing the establishment of an immune response in the microenvironment in which it`s expressed. When activated, it`s responsible for catabolizing the amino acid tryptophan, depriving cells in proliferation of this component generating metabolites that induce apoptosis. Hormones such as estrogen and progesterone are capable of alter immune functions in cells and may lead to altered expression of IDO, but the mechanisms responsible for this effect are still unclear. It is known that several tumor cells and leucocytes adjacent to the tumor region are able to express IDO and are sensitive to the action of these hormones. Breast carcinomas are the most common in female dogs, presenting a great expression of IDO. Bearing this information, this study aimed to investigate the influence of estrogen and progesterone on the expression of IDO in culture of mammary carcinoma cells from bitches treated with these hormones and their respective receptor antagonists (tamoxifen - estrogen and mifepristone - progesterone). The expression of the enzyme was analyzed by immunohistochemistry, flow cytometry and quantified by the western blot technique, while the mRNA was analyzed by Real-time PCR. The results of enzyme quantification (flow cytometry and Western blot) followed the same pattern of mRNA expression. There was an increase of the enzyme expression and mRNA in the estrogen treated group, in contrast to the decrease observed in the progesterone group. When the cells were subjected to the hormonal inhibitors, an evident decrease of IDO expression percentage and the respective mRNA was verified following the supplementation of tamoxifen and a restoration of IDO expression values and the mRNA after the addition of the progesterone inhibitor, mifepristone. With these findings, we conclude that steroid hormones due to the modifications in the cytokine patterns expressed by PR and ER positive cells in the tumor microenvironment alters IDO expression.

The emergence of tamoxifen or aromatase inhibitor resistance is a major problem in the treatment of breast cancer. The molecular signaling mechanism of antiestrogen resistance is not clear. Understanding the mechanisms by which resistance to these agents arise could have major clinical implications for preventing or circumventing it. Therefore, in this dissertation we have investigated the molecular mechanisms underlying antiestrogen resistance by studying the contributions of reactive oxygen species (ROS)-induced redox signaling pathways in antiestrogen resistant breast cancer cells. Our hypothesis is that the conversion of breast tumors to a tamoxifen-resistant phenotype is associated with a progressive shift towards a pro-oxidant environment of cells as a result of oxidative stress. The hypothesis of this dissertation was tested in an in vitro 2-D cell culture model employing state of the art biochemical and molecular techniques, including gene overexpression, immunoprecipitation, Western blotting, confocal imaging, ChIP, Real-Time RT-PCR, and anchorage-independent cell growth assays. We observed that tamoxifen (TAM) acts like both an oxidant and an antioxidant. Exposure of tamoxifen resistant LCC2 cell to TAM or 17 beta-estradiol (E2) induced the formation of reactive oxidant species (ROS). The formation of E2-induced ROS was inhibited by co-treatment with TAM, similar to cells pretreated with antioxidants. In LCC2 cells, treatments with either E2 or TAM were capable of inducing cell proliferation which was then inhibited by biological and chemical antioxidants. Exposure of LCC2 cells to tamoxifen resulted in a decrease in p27 expression. The LCC2 cells exposed to TAM showed an increase in p27 phosphorylation on T157 and T187. Conversely, antioxidant treatment showed an increase in p27 expression and a decrease in p27 phosphorylation on T157 and T187 in TAM exposed cells which were similar to the effects of Fulvestrant. In line with previous studies, we showed an increase in the binding of cyclin E–Cdk2 and in the level of p27 in TAM exposed cells that overexpressed biological antioxidants. Together these findings highly suggest that lowering the oxidant state of antiestrogen resistant LCC2 cells, increases LCC2 susceptibility to tamoxifen via the cyclin dependent kinase inhibitor p27.