RESUMO
Membrane overexpression of ErbB-2 (MErbB-2), a member of the ErbB family of receptor tyrosine kinases, occurs in 15-20% of breast cancers (BC) and constitutes a therapeutic target in this BC subtype (ErbB-2-positive). Although MErbB-2-targeted therapies have significantly improved patients' clinical outcome, resistance to available drugs is still a major issue in the clinic. Lack of accurate biomarkers for predicting responses to anti-ErbB-2 drugs at the time of diagnosis is also an important unresolved issue. Hence, a better understanding of the ErbB-2 signaling pathway constitutes a critical task in the battle against BC. In its canonical mechanism of action, MErbB-2 activates downstream signaling pathways, which transduce its proliferative effects in BC. The dogma of ErbB-2 mechanism of action has been challenged by the demonstration that MErbB-2 migrates to the nucleus, where it acts as a transcriptional regulator. Accumulating findings demonstrate that nuclear ErbB-2 (NErbB-2) is involved in BC growth and metastasis. Emerging evidence also reveal a role of NErbB-2 in the response to available anti-MErbB-2 agents. Here, we will review NErbB-2 function in BC and will particularly discuss the role of NErbB-2 as a novel target for therapy in ErbB-2-positive BC.
Assuntos
Neoplasias da Mama/metabolismo , Terapia de Alvo Molecular , Receptor ErbB-2/metabolismo , Antineoplásicos/uso terapêutico , Apoptose , Biomarcadores , Biomarcadores Tumorais/metabolismo , Neoplasias da Mama/tratamento farmacológico , Núcleo Celular/metabolismo , Sobrevivência Celular , Resistencia a Medicamentos Antineoplásicos , Feminino , Humanos , Metástase Neoplásica , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Transdução de Sinais , Resultado do TratamentoRESUMO
Aproximadamente 15-20% de los cánceres de mama (CM) presentan sobre- expresión en la membrana citoplasmática de ErbB-2 (MErbB-2), un miembro de la familia ErbBs de receptores con actividad de tirosina quinasa, o bien presentan amplificación del gen. Antes del desarrollo de terapias dirigidas contra el MErbB-2, este subtipo de CM, denominado ErbB-2-positivo, estaba asociado con un aumento en el potencial metastásico del tumor y un mal pronóstico. Estas terapias han aumentado significativamente la sobrevida global y el porcentaje de enfermos curados. Sin embargo, la resistencia a las terapias disponibles actualmente es todavía un importante problema en la clínica. Actuando por su mecanismo clásico, el MErbB-2 activa cascadas de señalización que transducen sus efectos en el cáncer de mama. La presencia del ErbB-2 en el núcleo fue descubierta hace más de veinte años. Evidencias experimentales proporcionadas por varios grupos de investigación, incluyendo el nuestro, revelaron una función no canónica del ErbB-2 en el núcleo celular donde actúa como un regulador de transcripción. Nuestros hallazgos demostraron que el ErbB-2 nuclear estimula el crecimiento del CM, el desarrollo de metástasis y la resistencia a las terapias utilizadas actualmente
Membrane overexpression of ErbB-2 (MErbB-2), a member of the ErbBs family of receptor tyrosine kinases, or ErbB-2 gene amplification, occurs in 15-20% of breast cancers (BC). Until the development of MErbB-2-targeted therapies, this BC subtype, called ErbB-2-positive, was associated with increased metastatic potential and poor prognosis. Although the overall survival and cure rates have improved significantly with such therapies, resistance to available drugs is still a major clinical issue. In its classical mechanism, MErbB-2 activates downstream signal cascades, which transduce its effects in BC. The fact that ErbB-2 is also present at the nucleus of BC cells was discovered over twenty years ago. Also, compelling evidence revealed a non-canonical function of nuclear ErbB-2 as a transcriptional regulator. Since deeper understanding of nuclear ErbB-2 actions would be critical to disclose its role as a biomarker and a target of therapy in BC, we will here review its function in BC, focusing on its role in growth, metastatic spreading, and response to currently available MErbB-2 positive BC therapies.
Assuntos
Humanos , Neoplasias da Mama/terapia , Núcleo Celular , Receptor ErbB-2 , Genes erbB-2RESUMO
The aim of the current study was to search for the presence of genetic variants in the CYP21A2 Z promoter regulatory region in patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency. Screening of the 10 most frequent pseudogene-derived mutations was followed by direct sequencing of the entire coding sequence, the proximal promoter, and a distal regulatory region in DNA samples from patients with at least one non-determined allele. We report three non-classical patients that presented a novel genetic variant-g.15626A>G-within the Z promoter regulatory region. In all the patients, the novel variant was found in cis with the mild, less frequent, p.P482S mutation located in the exon 10 of the CYP21A2 gene. The putative pathogenic implication of the novel variant was assessed by in silico analyses and in vitro assays. Topological analyses showed differences in the curvature and bendability of the DNA region bearing the novel variant. By performing functional studies, a significantly decreased activity of a reporter gene placed downstream from the regulatory region was found by the G transition. Our results may suggest that the activity of an allele bearing the p.P482S mutation may be influenced by the misregulated CYP21A2 transcriptional activity exerted by the Z promoter A>G variation.
Assuntos
Hiperplasia Suprarrenal Congênita/genética , Alelos , Regiões Promotoras Genéticas , Esteroide 21-Hidroxilase/genética , Feminino , Regulação da Expressão Gênica , Humanos , Masculino , MutaçãoRESUMO
Fragile X mental retardation protein (FMRP) belongs to a small family of RNA-binding proteins. Its absence or inactivity is responsible for fragile X syndrome, the most common cause of inherited mental retardation. Despite its ubiquitous expression, FMRP function and expression remain almost understudied in non-neuronal tissues, though previous studies on germline development during oogenesis may suggest a special function of this protein also in ovarian tissue. In addition, the well-documented association of FMR1 premutation state with fragile X-related premature ovarian insufficiency adds interest to the role of FMRP in ovarian physiology. The aim of the present work was to investigate the expression of Fmr1 mRNA and its protein, FMRP, at different stages of rat follicular development. By immunohistochemical studies we demonstrated FMRP expression in granulosa, theca and germ cells in all stages of follicular development. In addition, changes in Fmr1 expression, both at the protein and mRNA levels, were observed. FMRP levels increased upon follicular development while preantral and early antral follicles presented similar levels of Fmr1 transcripts with decreased expression in preovulatory follicles. These observations suggest that Fmr1 expression in the ovary is regulated at different and perhaps independent levels. In addition, our results show expression of at least four different isoforms of FMRP during all stages of follicular growth with expression patterns that differ from those observed in brain and testis. Our study shows a regulated expression of Fmr1, both at mRNA and protein levels, during rat follicular development.
Assuntos
Proteína do X Frágil da Deficiência Intelectual/genética , Folículo Ovariano/metabolismo , Animais , Feminino , Proteína do X Frágil da Deficiência Intelectual/metabolismo , Folículo Ovariano/crescimento & desenvolvimento , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-DawleyRESUMO
Aberrant Stat3 activation and signaling contribute to malignant transformation by promoting cell cycle progression, inhibiting apoptosis, and mediating tumor immune evasion. Stat3 inhibition in tumor cells induces the expression of chemokines and proinflammatory cytokines, so we proposed to apply Stat3-inhibited breast cancer cells as a source of immunogens to induce an antitumor immune response. Studies were performed in two murine breast cancer models in which Stat3 is activated: progestin-dependent C4HD cells and 4T1 cells. We immunized BALB/c mice with irradiated cancer cells previously transfected with a dominant-negative Stat3 vector (Stat3Y705F) in either a prophylactic or a therapeutic manner. Prophylactic administration of breast cancer cells transfected with Stat3Y705F (Stat3Y705F-breast cancer cells) inhibited primary tumor growth compared with administration of empty vector-transfected cells in both models. In the 4T1 model, 50% of the challenged mice were tumor free, and the incidence of metastasis decreased by 90%. In vivo assays of C4HD tumors showed that the antitumor immune response involves the participation of CD4(+) T cells and cytotoxic NK cells. Therapeutic immunization with Stat3Y705F-breast cancer cells inhibited tumor growth, promoted tumor cell differentiation, and decreased metastasis. Furthermore, inhibition of Stat3 activation in breast cancer cells induced cellular senescence, contributing to their immunogenic phenotype. In this work, we provide preclinical proof of concept that ablating Stat3 signaling in breast cancer cells results in an effective immunotherapy against breast cancer growth and metastasis. Moreover, our findings showing that Stat3 inactivation results in induction of a cellular senescence program disclose a potential mechanism for immunotherapy research.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Senescência Celular/imunologia , Marcação de Genes , Células Matadoras Naturais/imunologia , Neoplasias Mamárias Animais/imunologia , Neoplasias Mamárias Animais/terapia , Animais , Linfócitos T CD4-Positivos/metabolismo , Linfócitos T CD4-Positivos/patologia , Linhagem Celular Tumoral , Quimiocinas/metabolismo , Citocinas/metabolismo , Modelos Animais de Doenças , Feminino , Marcação de Genes/métodos , Células Matadoras Naturais/metabolismo , Células Matadoras Naturais/patologia , Neoplasias Mamárias Animais/patologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Cultura Primária de Células , Fator de Transcrição STAT3RESUMO
BACKGROUND: The biological relevance of nuclear ErbB-2/HER2 (NuclErbB-2) presence in breast tumors remains unexplored. In this study we assessed the clinical significance of ErbB-2 nuclear localization in primary invasive breast cancer. The reporting recommendations for tumor marker prognostic studies (REMARK) guidelines were used as reference. METHODS: Tissue microarrays from a cohort of 273 primary invasive breast carcinomas from women living in Chile, a Latin American country, were examined for membrane (MembErbB-2) and NuclErbB-2 expression by an immunofluorescence (IF) protocol we developed. ErbB-2 expression was also evaluated by immunohistochemistry (IHC) with a series of antibodies. Correlation between NuclErbB-2 and MembErbB-2, and between NuclErbB-2 and clinicopathological characteristics of tumors was studied. The prognostic value of NuclErbB-2 in overall survival (OS) was evaluated using Kaplan-Meier method, and Cox model was used to explore NuclErbB-2 as independent prognostic factor for OS. RESULTS: The IF protocol we developed showed significantly higher sensitivity for detection of NuclErbB-2 than IHC procedures, while its specificity and sensitivity to detect MembErbB-2 were comparable to those of IHC procedures. We found 33.6% NuclErbB-2 positivity, 14.2% MembErbB-2 overexpression by IF, and 13.0% MembErbB-2 prevalence by IHC in our cohort. We identified NuclErbB-2 positivity as a significant independent predictor of worse OS in patients with MembErbB-2 overexpression. NuclErbB-2 was also a biomarker of lower OS in tumors that overexpress MembErbB-2 and lack steroid hormone receptors. CONCLUSIONS: We revealed a novel role for NuclErbB-2 as an independent prognostic factor of poor clinical outcome in MembErbB-2-positive breast tumors. Our work indicates that patients presenting NuclErbB-2 may need new therapeutic strategies involving specific blockage of ErbB-2 nuclear migration.