RESUMEN
N-cadherin and HER2/neu were found to be co-expressed in invasive breast carcinomas. To test the contribution of N-cadherin and HER2 in mammary tumor metastasis, we targeted N-cadherin expression in the mammary epithelium of the MMTV-Neu mouse. In the context of ErbB2/Neu, N-cadherin stimulated carcinoma cell invasion, proliferation and metastasis. N-cadherin caused fibroblast growth factor receptor (FGFR) upmodulation, resulting in epithelial-to-mesenchymal transition (EMT) and stem/progenitor like properties, involving Snail and Slug upregulation, mammosphere formation and aldehyde dehydrogenase activity. N-cadherin potentiation of the FGFR stimulated extracellular signal regulated kinase (ERK) and protein kinase B (AKT) phosphorylation resulting in differential effects on metastasis. Although ERK inhibition suppressed cyclin D1 expression, cell proliferation and stem/progenitor cell properties, it did not affect invasion or EMT. Conversely, AKT inhibition suppressed invasion through Akt 2 attenuation, and EMT through Snail inhibition, but had no effect on cyclin D1 expression, cell proliferation or mammosphere formation. These findings suggest N-cadherin/FGFR has a pivotal role in promoting metastasis through differential regulation of ERK and AKT, and underscore the potential for targeting the FGFR in advanced ErbB2-amplified breast tumors.
Asunto(s)
Neoplasias de la Mama/patología , Cadherinas/genética , Transición Epitelial-Mesenquimal , Quinasas MAP Reguladas por Señal Extracelular/biosíntesis , Proteínas Proto-Oncogénicas c-akt/metabolismo , Receptores de Factores de Crecimiento de Fibroblastos/genética , Aldehído Deshidrogenasa/biosíntesis , Animales , Benzamidas/farmacología , Cadherinas/biosíntesis , Movimiento Celular/genética , Proliferación Celular , Ciclina D1/biosíntesis , Difenilamina/análogos & derivados , Difenilamina/farmacología , Transición Epitelial-Mesenquimal/genética , Quinasas MAP Reguladas por Señal Extracelular/antagonistas & inhibidores , Femenino , Humanos , Neoplasias Pulmonares/secundario , MAP Quinasa Quinasa 1/antagonistas & inhibidores , Ratones , Ratones Transgénicos , Invasividad Neoplásica , Metástasis de la Neoplasia , Fosforilación , Proteínas Proto-Oncogénicas c-akt/genética , Pirimidinas/farmacología , Interferencia de ARN , ARN Interferente Pequeño , Receptor ErbB-2/antagonistas & inhibidores , Receptor ErbB-2/biosíntesis , Receptor ErbB-2/genética , Receptores de Factores de Crecimiento de Fibroblastos/antagonistas & inhibidores , Receptores de Factores de Crecimiento de Fibroblastos/biosíntesis , Transducción de Señal/genética , Factores de Transcripción de la Familia Snail , Esferoides Celulares/patología , Células Madre/metabolismo , Factores de Transcripción/antagonistas & inhibidores , Factores de Transcripción/biosíntesis , Células Tumorales CultivadasRESUMEN
Cell proliferation and invasion are critical for malignant progression, yet how these processes relate to each other and whether they regulate one another during metastasis is unknown. We show that invasiveness of breast cancer cells is associated with growth arrest due to p21CIP1 upregulation. Knockdown of p21CIP1 increases cell proliferation and suppresses invasion. Since p21CIP1 acts to inhibit cyclin E during cell-cycle progression, we demonstrated that a constitutively active form of cyclin E had similar effects to p21CIP1 inhibition resulting in enhanced cell growth and suppressed invasiveness. We tested these findings in vivo in the Polyoma middle T mammary tumor model in which p21CIP1 was deleted. p21CIP1 knockout mice exhibited dramatic suppression of metastasis, independent of tumor growth, which was rescued by p21CIP1. Metastasis suppression by p21CIP1 ablation was associated with striking cytoskeletal reorganization leading to a non-invasive and highly proliferative state. Thus, p21CIP1 regulates metastasis by mediating reciprocal switching between invasion and proliferation.
Asunto(s)
Neoplasias de la Mama/genética , Neoplasias de la Mama/patología , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/genética , Metástasis de la Neoplasia/patología , Animales , Neoplasias de la Mama/metabolismo , Movimiento Celular/genética , Proliferación Celular , Ciclina E/metabolismo , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/metabolismo , Citoesqueleto/genética , Citoesqueleto/metabolismo , Femenino , Puntos de Control de la Fase G1 del Ciclo Celular/genética , Técnicas de Inactivación de Genes , Humanos , Neoplasias Mamarias Experimentales/genética , Neoplasias Mamarias Experimentales/patología , Ratones , Ratones Transgénicos , Metástasis de la Neoplasia/genéticaRESUMEN
Caveolin-1 is a 22-kDa integral membrane protein that has been suggested to function as a negative regulator of mitogen-stimulated proliferation in a variety of cell types, including mammary epithelial cells. Because much of our insight into caveolin-1 function has come from the study of human breast tumor-derived cell lines in culture, the normal physiological regulators of caveolin-1 expression in the mammary gland remain unknown. Here, we examine caveolin-1 expression in mice at different stages of mammary gland development. We show that caveolin-1 expression is significantly down-regulated during late pregnancy and lactation. Upon weaning, mammary gland expression of caveolin-1 rapidly returns to non-pregnant "steady-state" levels. Injection of virgin mice with a battery of hormones normally up-regulated during lactation demonstrates that prolactin is the main mediator of caveolin-1 down-regulation. Virtually identical results were obtained with human mammary epithelial cells (hTERT-HME1) in culture. In addition, we demonstrate that prolactin-mediated down-regulation of caveolin-1 expression occurs at the level of transcriptional control and via a Ras-dependent mechanism. Interestingly, in the mammary gland, both mammary epithelial cells and the surrounding mammary adipocytes show prolactin-mediated down-regulation of caveolin-1. This hormone-dependent regulation of caveolin-1 expression is specific to the mammary fat pad. Finally, we employed HC11 cells, a well-established model of mammary epithelial cell differentiation, to study the possible functional effects of caveolin-1 expression. In the presence of lactogenic hormones, recombinant expression of caveolin-1 in HC11 cells dramatically suppresses the induction of the promoter activity and the synthesis of beta-casein, an established reporter of lactogenic differentiation and milk production. These findings may explain why caveolin-1 levels are normally down-regulated during lactation. This report is the first demonstration that caveolin-1 levels are down-regulated during a normal physiological event in vivo, i.e. lactation, because previous reports have only documented that down-regulation of caveolin-1 occurs during cell transformation and tumorigenesis.
Asunto(s)
Caveolinas/genética , Regulación hacia Abajo/fisiología , Lactancia/genética , Glándulas Mamarias Animales/metabolismo , Proteína Oncogénica p21(ras)/fisiología , Prolactina/fisiología , Animales , Secuencia de Bases , Caseínas/biosíntesis , Caveolina 1 , Diferenciación Celular , Línea Celular , Cartilla de ADN , Células Epiteliales/metabolismo , Sistema de Señalización de MAP Quinasas , Glándulas Mamarias Animales/citología , Ratones , Ratones Endogámicos C57BLRESUMEN
Breast cancer arises from multiple genetic events that together contribute to the established, irreversible malignant phenotype. The development of inducible tissue-specific transgenics has allowed a careful dissection of the events required for induction and subsequent maintenance of tumorigenesis. Mammary gland targeted expression of oncogenic Ras or c-Myc is sufficient for the induction of mammary gland tumorigenesis in the rodent, and when overexpressed together the rate of tumor onset is substantially enhanced. In an exciting recent finding, D'Cruz et al discovered tetracycline-regulated c-Myc overexpression in the mammary gland induced invasive mammary tumors that regressed upon withdrawal of c-Myc expression. Almost one-half of the c-Myc-induced tumors harbored K-ras or N-ras gene point mutations, correlating with tumor persistence on withdrawal of c-Myc transgene expression. These findings suggest maintenance of tumorigenesis may involve a second mutation within the Ras pathway.
Asunto(s)
Neoplasias de la Mama/genética , Neoplasias de la Mama/fisiopatología , Transformación Celular Neoplásica , Regulación Neoplásica de la Expresión Génica , Genes myc/genética , Genes ras/genética , Neoplasias Mamarias Animales/genética , Neoplasias Mamarias Animales/fisiopatología , Animales , Animales Modificados Genéticamente , Modelos Animales de Enfermedad , Femenino , Humanos , Ratones , RatasRESUMEN
Breast cancer is the most commonly diagnosed cancer in American women. The underlying mechanisms that cause aberrant cell proliferation and tumor growth involve conserved pathways, which include components of the cell cycle machinery. Proto-oncogenes, growth factors, and steroids have been implicated in the pathogenesis of breast cancer. Surgery, local irradiation, and chemotherapy have been the mainstay of treatment for early and advanced stage disease. Potential targets for selective breast cancer therapy are herein reviewed. Improved understanding of the biology of breast cancer has led to more specific "targeted therapies" directed at biological processes that are selectively deregulated in the cancerous cells. Examples include tamoxifen for estrogen receptor positive tumors and imunoneutralizing antibodies such as trastuzumab for Her2/neu overexpressing tumors. Other novel anticancer agents such as paclitaxel, a microtubule binding molecule, and flavopiridol, a cyclin dependent kinase inhibitor, exert their anticancer effects by inhibiting cell cycle progression.
Asunto(s)
Adenocarcinoma/tratamiento farmacológico , Neoplasias de la Mama/tratamiento farmacológico , Proteínas de Ciclo Celular , Proteínas Supresoras de Tumor , Adenocarcinoma/genética , Adenocarcinoma/metabolismo , Adenocarcinoma/patología , Animales , Anticuerpos Monoclonales/uso terapéutico , Anticuerpos Monoclonales Humanizados , Antineoplásicos/uso terapéutico , Neoplasias de la Mama/genética , Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/patología , Ciclo Celular/efectos de los fármacos , Inhibidor p27 de las Quinasas Dependientes de la Ciclina , Ciclinas/metabolismo , Bases de Datos Factuales , Inhibidores Enzimáticos/uso terapéutico , Flavonoides/uso terapéutico , Humanos , Proteínas Asociadas a Microtúbulos/genética , Proteínas Asociadas a Microtúbulos/metabolismo , Neovascularización Patológica , Oncogenes , Paclitaxel/uso terapéutico , Piperidinas/uso terapéutico , Receptores de Estrógenos/metabolismo , Tamoxifeno/uso terapéutico , Factor de Crecimiento Transformador beta/genética , Factor de Crecimiento Transformador beta/metabolismo , TrastuzumabRESUMEN
The cyclin D1 gene encodes the regulatory subunit of a holoenzyme that phosphorylates and inactivates the pRB tumor suppressor protein. Cyclin D1 is overexpressed in 20-30% of human breast tumors and is induced both by oncogenes including those for Ras, Neu, and Src, and by the beta-catenin/lymphoid enhancer factor (LEF)/T cell factor (TCF) pathway. The ankyrin repeat containing serine-threonine protein kinase, integrin-linked kinase (ILK), binds to the cytoplasmic domain of beta(1) and beta(3) integrin subunits and promotes anchorage-independent growth. We show here that ILK overexpression elevates cyclin D1 protein levels and directly induces the cyclin D1 gene in mammary epithelial cells. ILK activation of the cyclin D1 promoter was abolished by point mutation of a cAMP-responsive element-binding protein (CREB)/ATF-2 binding site at nucleotide -54 in the cyclin D1 promoter, and by overexpression of either glycogen synthase kinase-3beta (GSK-3beta) or dominant negative mutants of CREB or ATF-2. Inhibition of the PI 3-kinase and AKT/protein kinase B, but not of the p38, ERK, or JNK signaling pathways, reduced ILK induction of cyclin D1 expression. ILK induced CREB transactivation and CREB binding to the cyclin D1 promoter CRE. Wnt-1 overexpression in mammary epithelial cells induced cyclin D1 mRNA and targeted overexpression of Wnt-1 in the mammary gland of transgenic mice increased both ILK activity and cyclin D1 levels. We conclude that the cyclin D1 gene is regulated by the Wnt-1 and ILK signaling pathways and that ILK induction of cyclin D1 involves the CREB signaling pathway in mammary epithelial cells.
Asunto(s)
Proteínas Quinasas Dependientes de Calcio-Calmodulina/metabolismo , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/metabolismo , Ciclina D1/genética , Regulación de la Expresión Génica , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas de Pez Cebra , Factor de Transcripción Activador 2 , Animales , Neoplasias de la Mama , Antígenos CD18/fisiología , Línea Celular , Células Epiteliales/metabolismo , Femenino , Regulación Neoplásica de la Expresión Génica , Glucógeno Sintasa Quinasa 3 , Glucógeno Sintasa Quinasas , Humanos , Integrina beta1/fisiología , Glándulas Mamarias Animales/citología , Glándulas Mamarias Animales/metabolismo , Ratones , Ratones Transgénicos , Regiones Promotoras Genéticas , Proteínas Serina-Treonina Quinasas/genética , Subunidades de Proteína , Proteínas Tirosina Quinasas/metabolismo , Proteínas Proto-Oncogénicas/metabolismo , Transducción de Señal , Factores de Transcripción/metabolismo , Transfección , Células Tumorales Cultivadas , Proteínas Wnt , Proteína Wnt1RESUMEN
The cyclin D1 gene encodes the regulatory subunit of the holoenzyme that phosphorylates and inactivates the retinoblastoma pRB protein. Cyclin D1 protein levels are elevated by mitogenic and oncogenic signaling pathways, and antisense mRNA to cyclin D1 inhibits transformation by the ras, neu, and src oncogenes, thus linking cyclin D1 regulation to cellular transformation. Caveolins are the principal protein components of caveolae, vesicular plasma membrane invaginations that also function in signal transduction. We show here that caveolin-1 expression levels inversely correlate with cyclin D1 abundance levels in transformed cells. Expression of antisense caveolin-1 increased cyclin D1 levels, whereas caveolin-1 overexpression inhibited expression of the cyclin D1 gene. Cyclin D1 promoter activity was selectively repressed by caveolin-1, but not by caveolin-3, and this repression required the caveolin-1 N terminus. Maximal inhibition of the cyclin D1 gene promoter by caveolin-1 was dependent on the cyclin D1 promoter T-cell factor/lymphoid enhancer factor-1-binding site between -81 to -73. The T-cell factor/lymphoid enhancer factor sequence was sufficient for repression by caveolin-1. We suggest that transcriptional repression of the cyclin D1 gene may contribute to the inhibition of transformation by caveolin-1.