RESUMO
The transmembrane tyrosine kinase HER2 (ErbB2, neu) is a prototypical biomarker for breast cancers and a therapeutic target. Although anti-HER2 therapies are remarkably effective, HER2-positive tumors are heterogeneous and some subtypes do not respond or develop resistance to these therapies. Here we show that H2NTF, a novel N-terminal fragment of HER2, is expressed at variable levels in 60% of the breast cancer samples analyzed. Characterization of H2NTF shows that it is devoid of the tyrosine kinase domain but it readily interacts with full-length HER2 and other HER receptors. As a consequence, H2NTF acts as a dominant-negative, attenuating the signaling triggered by full-length HER receptors. Expression of H2NTF results in resistance to the treatment with low concentrations of trastuzumab in vitro. However, cells expressing H2NTF and non-expressing cells have similar sensitivity to trastuzumab in vivo, indicating that H2NTF/trastuzumab complexes trigger antibody-dependent cell-mediated cytotoxicity.
Assuntos
Neoplasias da Mama/genética , Carcinoma/genética , Receptor ErbB-2/química , Receptor ErbB-2/genética , Sequência de Aminoácidos , Animais , Neoplasias da Mama/epidemiologia , Carcinoma/epidemiologia , Feminino , Regulação Neoplásica da Expressão Gênica , Frequência do Gene , Genes Dominantes , Células HEK293 , Humanos , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos NOD , Camundongos Nus , Camundongos SCID , Modelos Biológicos , Dados de Sequência Molecular , Isoformas de Proteínas/química , Isoformas de Proteínas/genética , Estrutura Terciária de Proteína/genética , Estrutura Terciária de Proteína/fisiologia , Receptor ErbB-2/metabolismo , Células Tumorais CultivadasRESUMO
Body weight control is tightly regulated in the hypothalamus. The inaccessibility of human brain tissue can be partially solved by using cerebrospinal fluid (CSF) as a tool for assessing the central nervous system's production of orexigen and anorexigen factors. Using proteomic analysis, the present study investigated the differentially displayed proteins in human CSF from obese and non-obese subjects. We designed a case-control study conducted in a reference hospital where eight obese (cases) and eight non-obese (controls) women with idiopathic intracranial hypertension were included. Intracranial hypertension was normalised through the placement of a ventriculo- or lumboperitoneal shunt in the 12 months before their inclusion in the study. Isotope-coded protein label (for proteins > 10 kDa) and label-free liquid chromatography (for proteins < 10 kDa) associated with mass spectrometry analysis were used. Eighteen differentially expressed proteins were identified. Many of them fall into three main groups: inflammation (osteopontin, fibrinogen γ and ß chain, α1 acid glycoprotein 2 and haptoglobin), neuroendocrine mediators (neurosecretory protein VGF, neuroendocrine protein 7B2, chromogranin-A and chromogranin B), and brain plasticity (testican-1, isoform 10 of fibronectin, galectin-3 binding protein and metalloproteinase inhibitor type 2). The differential production of osteopontin, neurosecretory protein VGF, chromogranin-A and fibrinogen γ chain was further confirmed by either enzyme-linked immunosorbent assay or western blotting. In conclusion, we have identified potential candidates that could be involved in the pathogenesis of obesity. Further studies aiming to investigating the precise role of these proteins in the pathogenesis of obesity and their potential therapeutic implications are needed.
Assuntos
Obesidade/etiologia , Proteômica/métodos , Pseudotumor Cerebral/líquido cefalorraquidiano , Adulto , Estudos de Casos e Controles , Feminino , Humanos , Pessoa de Meia-Idade , Obesidade/líquido cefalorraquidiano , Obesidade/fisiopatologia , Estudos ProspectivosRESUMO
The activity of a variety of extracellular signaling factors is tightly regulated by proteins containing A Disintegrin And a Metalloprotease domain (ADAM) metalloproteases through limited proteolysis. Thus, the identification of ADAM substrates may unveil novel components and mechanisms of cell signaling pathways. We report the identification of the transmembrane protein vasorin (VASN), a transforming growth factor-ß (TGFß) trap, as a substrate of ADAM17. The metalloprotease efficiently generates a soluble fragment encompassing the extracellular domain of VASN. Despite the importance of TGFß in normal development and tumor progression, the regulation of VASN is completely unknown. Here, we show that only the soluble form of VASN inhibits TGFß and that the secretion of VASN is tightly controlled by ADAM17. Hence, inhibition of ADAM17 leads to the upregulation of TGFß signaling. Adding a new level of complexity to the function of ADAM17, we finally show that, through the cleavage of VASN, the metalloprotease controls TGFß-mediated epithelial-to-mesenchymal transition.