VEGF-mediated angiogenesis of human pheochromocytomas is associated to malignancy and inhibited by anti-VEGF antibodies in experimental tumors.
BACKGROUND
Pheochromocytomas are well-vascularized tumors of the adrenal medulla. In human pheochromocytomas, angiogenesis has been associated with tumor progression. The mechanisms, however, are unknown.


METHODS
Surgical specimens of benign, invasive, and metastatic human pheochromocytomas (n = 10/5/5) were immunostained for vascular endothelial growth factor (VEGF) and CD34, to determine VEGF expression and microvessel density (vascular surface density, [VSD]). In PC12-pheochromocytoma cells, VEGF messenger RNA and protein were analyzed by Northern blotting and enzyme immunoassay; biologic activity by human umbilical vein endothelial cell-proliferation assay. Inhibition of angiogenesis of PC12 xenografts by 2 neutralizing anti-VEGF antibodies (C20-pAB, M461-mAB) was evaluated by VEGF expression, VSD, and mitotic activity.


RESULTS
VEGF expression and VSD were significantly higher in metastatic pheochromocytomas (VEGF 37.1 +/- 10.9% vs 20.7 +/- 9%, VSD 26.2 +/- 8 vs 13.5 +/- 3.3 1/mm). VEGF messenger RNA and protein were confirmed in PC12 cells and stimulated by nerve growth factor. Conditioned PC12 medium increased human umbilical vein endothelial cell proliferation more than 2-fold. Xentrotransplanted PC12 cells had marked VEGF expression and angiogenesis, which was inhibited by anti-VEGF antibodies (VEGF-expression by 29 and 38%, VSD by 43 and 46%, P <.05).


CONCLUSIONS
Higher VEGF expression and microvessel density in malignant pheochromocytomas suggest VEGF-mediated angiogenesis to be related to tumor progression. Angiogenesis of PC12 xenografts is mediated by VEGF. Neutralizing anti-VEGF antibodies inhibit angiogenesis in experimental pheochromocytomas and may have potential for treating nonresectable pheochromocytomas.
Zielke
Andreas
A
Department of Surgery, Philipps-University of Marburg, 35043 Marburg, Germany.
Middeke
Martin
M
Hoffmann
Sebastian
S
Colombo-Benkmann
Mario
M
Barth
Peter
P
Hassan
Iyad
I
Wunderlich
Annette
A
Hofbauer
Lorenz C
LC
Duh
Quan-Yang
QY
D000310:Adrenal Gland Neoplasms / Q000378:metabolism / Q000628:therapy*; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D002455:Cell Division; D016228:Endothelial Growth Factors / Q000276:immunology / Q000378:metabolism*; D005260:Female; D007167:Immunotherapy; D066298:In Vitro Techniques; D036341:Intercellular Signaling Peptides and Proteins / Q000276:immunology / Q000378:metabolism*; D008222:Lymphokines / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D009389:Neovascularization, Pathologic / Q000378:metabolism / Q000628:therapy*; D016716:PC12 Cells; D010673:Pheochromocytoma / Q000378:metabolism / Q000628:therapy*; D051381:Rats; D013047:Specific Pathogen-Free Organisms; D014183:Transplantation, Heterologous; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D000911:Antibodies, Monoclonal; D016228:Endothelial Growth Factors; D036341:Intercellular Signaling Peptides and Proteins; D008222:Lymphokines; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors