RESUMEN
Diffuse infiltration of malignant human glioma cells into surrounding brain structures occurs through the activation of multigenic programs. We recently showed that angiopoietin-2 (Ang2) induces glioma invasion through the activation of matrix metalloprotease-2 (MMP-2). Here, we report that up-regulation of Ang2, MMP-2, membrane type 1-MMP (MT1-MMP), and laminin 5 gamma 2 (LN 5 gamma 2) in tumor cells correlates with glioma invasion. Analyses of 57 clinical human glioma biopsies of World Health Organization grade I to IV tumors displaying a distinct invasive edge and 39 glioma specimens that only contain the central region of the tumor showed that Ang2, MMP-2, MT1-MMP, and LN 5 gamma 2 were co-overexpressed in invasive areas but not in the central regions of the glioma tissues. Statistical analyses revealed a significant link between the preferential expression of these molecules and invasiveness. Protein analyses of microdissected primary glioma tissue showed up-regulation and activation of MT1-MMP and LN 5 gamma 2 at the invasive edge of the tumors, supporting this observation. Concordantly, in human U87MG glioma xenografts engineered to express Ang2, increased expression of MT1-MMP and LN 5 gamma 2, along with MMP-2 up-regulation, in actively invading glioma cells was also evident. In cell culture, stimulation of glioma cells by overexpressing Ang2 or exposure to exogenous Ang2 promoted the expression and activation of MMP-2, MT1-MMP, and LN 5 gamma 2. These results suggest that up-regulation of Ang2, MMP-2, MT1-MMP, and LN 5 gamma 2 is associated with the invasiveness displayed by human gliomas and that induction of these molecules by Ang2 may be essential for glioma invasion.
Asunto(s)
Angiopoyetina 2/biosíntesis , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/patología , Regulación Neoplásica de la Expresión Génica , Glioma/patología , Laminina/biosíntesis , Metaloproteinasa 2 de la Matriz/biosíntesis , Metaloendopeptidasas/biosíntesis , Regulación hacia Arriba , Animales , Astrocitoma/metabolismo , Biopsia , Western Blotting , Encéfalo/patología , Línea Celular Tumoral , Humanos , Inmunohistoquímica , Operón Lac , Metaloproteinasa 14 de la Matriz , Metaloproteinasas de la Matriz Asociadas a la Membrana , Ratones , Invasividad Neoplásica , Trasplante de Neoplasias , Neovascularización Patológica , Factores de TiempoRESUMEN
Alteration of the phenotype of breast cancers from estrogen-dependent to estrogen-independent growth often leads to the failure of antiestrogenic tumor therapies. We report that overexpression of vascular endothelial growth factor (VEGF) by estrogen-dependent MCF-7 breast cancer cells could abolish estrogen-dependent tumor growth in ovariectomized mice. In the absence of estrogen, MCF-7 VEGF-expressing tumors with increased vessel density showed growth kinetics similar to, or even greater than, that of parental MCF-7 tumors with estrogen supplementation. Overexpression of VEGF by MCF-7 cells or treatment on parental MCF-7 cells with recombinant VEGF also stimulated cell proliferation in culture. Our data suggest that VEGF stimulation of MCF-7 tumor angiogenesis and growth is mediated by both autocrine and paracrine mechanisms.
Asunto(s)
Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/patología , Factores de Crecimiento Endotelial/biosíntesis , Estradiol/farmacología , Péptidos y Proteínas de Señalización Intercelular/biosíntesis , Linfocinas/biosíntesis , Animales , Neoplasias de la Mama/irrigación sanguínea , Neoplasias de la Mama/genética , División Celular/efectos de los fármacos , División Celular/fisiología , Factores de Crecimiento Endotelial/genética , Femenino , Humanos , Péptidos y Proteínas de Señalización Intercelular/genética , Operón Lac , Linfocinas/genética , Ratones , Ratones Desnudos , Neoplasias Hormono-Dependientes/irrigación sanguínea , Neoplasias Hormono-Dependientes/genética , Neoplasias Hormono-Dependientes/metabolismo , Neoplasias Hormono-Dependientes/patología , Neovascularización Patológica/genética , Neovascularización Patológica/metabolismo , Isoformas de Proteínas , Receptores de Factores de Crecimiento Endotelial Vascular/biosíntesis , Transfección , Células Tumorales Cultivadas , Factor A de Crecimiento Endotelial Vascular , Factores de Crecimiento Endotelial VascularRESUMEN
A hallmark of highly malignant human gliomas is their infiltration of the brain. We analyzed a large number of primary human glioma biopsies and found high levels of expression of an angiogenic regulator, angiopoietin-2 (Ang2), in the invasive areas, but not in the central regions, of those tumors. In the invasive regions where Ang2 was overexpressed, increased levels of matrix metalloprotease-2 (MMP-2) were also apparent. Consonant with these features, intracranial xenografts of glioma cells engineered to express Ang2 were highly invasive into adjacent brain parenchyma compared with isogenic control tumors. In regions of the Ang2-expressing tumors that were actively invading the brain, high levels of expression of MMP-2 and increased angiogenesis were also evident. A link between these two features was apparent, because stable expression of Ang2 by U87MG cells or treatment of several glioma cell lines with recombinant Ang2 in vitro caused activation of MMP-2 and acquisition of increased invasiveness. Conversely, MMP inhibitors suppressed Ang2-stimulated activation of MMP-2 and Ang2-induced cell invasion. These results suggest that Ang2 plays a critical role in inducing tumor cell infiltration, and that this invasive phenotype is caused by activation of MMP-2.