Immunohistochemical study of VEGF, angiopoietin 2 and their receptors in the neovascularization following microinjection of C6 glioma cells into rat brain.
BACKGROUND
Recent papers suggest that two angiogenic factors (angiopoietin 2 and vascular endothelial growth factor) cooperate in tumoral angiogenesis to support the growing tumor. The purpose of the present work was to demonstrate the existence of such cooperation in a longitudinal study of a brain tumor model during tumor growth by means of immunohistochemistry.


METHODS
The study was performed on 31 rats bearing C6 glioma. At different stages of tumor growth, the histological aspects were described and sections were immunostained for VEGF, Ang-2 and their receptors VEGFR-1, VEGFR-2 and Tie-2. Immunostaining was semi-quantitatively analyzed and the localization of immunostained cells was reported.


RESULTS
Ang-2 and Tie-2 were detected in the endothelial cells of vessels surrounded by tumor cells, occuring early in our study, with immunostaining taking place from day 4 to day 24. Immunostaining with VEGF (on tumoral cells) and VEGFR-2 (on endothelial cells) was present after 8 days of tumor growth. A clear increase of vessel density can be observed at the periphery of the tumors after 16 days of tumor growth. At that time, areas of necrosis were present in the tumor with concomitant VEGF and Ang-2 expression.


CONCLUSIONS
The present study demonstrated cooperation between the early effect of Ang-2 and the secondary effect of VEGF to elaborate new vessels in a longitudinal study of experimental brain tumors. This study is favorable to the new model of tumor angiogenesis, with successive vessel cooption, regression and growth mediated by angiopoietins and VEGF.
Péoch
Michel
M
Unité mixte Université Joseph Fourier/INSERM U438, LCR CEA, Grenoble, France. Michel.Peoch@chu-grenoble.fr
Farion
Régine
R
Hiou
Agnes
A
Le Bas
Jean François
JF
Pasquier
Basile
B
Rémy
Chantal
C
D042702:Angiopoietin-2; D000818:Animals; D001932:Brain Neoplasms / Q000098:blood supply / Q000473:pathology*; D016228:Endothelial Growth Factors / Q000032:analysis*; D005910:Glioma / Q000098:blood supply / Q000473:pathology*; D008222:Lymphokines / Q000032:analysis*; D009389:Neovascularization, Pathologic / Q000473:pathology*; D011506:Proteins / Q000032:analysis*; D011518:Proto-Oncogene Proteins / Q000032:analysis*; D051381:Rats; D020794:Receptor Protein-Tyrosine Kinases / Q000032:analysis* / Q000037:antagonists & inhibitors; D017978:Receptors, Growth Factor / Q000032:analysis*; D040262:Receptors, Vascular Endothelial Growth Factor; D042461:Vascular Endothelial Growth Factor A; D040281:Vascular Endothelial Growth Factor Receptor-1; D042442:Vascular Endothelial Growth Factors
D042702:Angiopoietin-2; D016228:Endothelial Growth Factors; D008222:Lymphokines; D011506:Proteins; D011518:Proto-Oncogene Proteins; D017978:Receptors, Growth Factor; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D020794:Receptor Protein-Tyrosine Kinases; D040262:Receptors, Vascular Endothelial Growth Factor; D040281:Vascular Endothelial Growth Factor Receptor-1