In situ expression of angiopoietins in astrocytomas identifies angiopoietin-2 as an early marker of tumor angiogenesis.
Exp Neurol
; 159(2): 391-400, 1999 Oct.
Article
em En
| MEDLINE
| ID: mdl-10506510
ABSTRACT
Angiopoietin-1 (Ang-1) and its naturally occurring antagonist angiopoietin-2 (Ang-2) are novel ligands that regulate tyrosine phosphorylation of the Tie2/Tek receptor on endothelial cells. Proper regulation of Tie2/Tek is absolutely required for normal vascular development, seemingly by regulating vascular remodeling and endothelial cell interactions with supporting pericytes/smooth muscle cells. We investigated the expression of Ang-1 and Ang-2 in human astrocytomas by in situ hybridization and compared them to the distribution of pericytes/smooth muscle cells by immunohistochemistry for alpha-smooth muscle actin (SMA). Ang-1 mRNA was localized in tumor cells and Ang-2 mRNA was detected in endothelial cells of hyperplastic and nonhyperplastic tumor vessels. Ang-2 was also expressed in partially sclerotic vessels and in vascular channels surrounded by tumor cells in brain adjacent to the tumor. Neither Ang-1 nor Ang-2 was detected in normal brain. Dynamic changes in SMA expression during glioma tumorigenesis appear to progress from fragmentation in early vascular hyperplasia to subsequent reassociation and enhanced expression in later stages of vascular proliferation in hyperplastic complexes in high-grade gliomas. All these vessels displaying dynamic changes in SMA immunoreactivity also expressed Ang-2 mRNA. Moreover, SMA immunoreactive intratumoral vascular channels lacking morphological evidence of hyperplasia also showed upregulation of Ang-2. These results suggest that angiopoietins are involved in the early stage of vascular activation and in advanced angiogenesis, and they identify Ang-2 as an early marker of glioma-induced neovascularization. The association between Ang-2 expression and alterations in SMA immunoreactivity suggests a role for Ang-2 in tumor-associated activation of pericytes/smooth muscle cells.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Astrocitoma
/
Encéfalo
/
Neoplasias Encefálicas
/
Proteínas
/
Regulação Neoplásica da Expressão Gênica
/
Neovascularização Patológica
Limite:
Humans
Idioma:
En
Revista:
Exp Neurol
Ano de publicação:
1999
Tipo de documento:
Article
País de afiliação:
Estados Unidos