The proangiogenic phenotype of tumor-derived endothelial cells is reverted by the overexpression of platelet-activating factor acetylhydrolase.
OBJECTIVE
We previously reported that human tumor-derived endothelial cells (TEC) have an angiogenic phenotype related to the autocrine production of several angiogenic factors. The purpose of the present study was to evaluate whether an enhanced synthesis of platelet-activating factor (PAF) might contribute to the proangiogenic characteristics of TEC and whether its inactivation might inhibit angiogenesis.


METHODS
To address the potential role of PAF in the proangiogenic characteristics of TEC, we engineered TEC to stably overexpress human plasma PAF-acetylhydrolase (PAF-AH), the major PAF-inactivating enzyme, and we evaluated in vitro and in vivo angiogenesis.


RESULTS
TECs were able to synthesize a significantly enhanced amount of PAF compared with normal human microvascular endothelial cells when stimulated with thrombin, vascular endothelial growth factor, or soluble CD154. Transfection of TEC with PAF-AH (TEC-PAF-AH) significantly inhibited apoptosis resistance and spontaneous motility of TEC. In addition, PAF and vascular endothelial growth factor stimulation enhanced the motility and adhesion of TEC but not of TEC-PAF-AH. In vitro, TEC-PAF-AH lost the characteristic ability of TEC to form vessel-like structures when plated on Matrigel. Finally, when cells were injected s.c. within Matrigel in severe combined immunodeficiency mice or coimplanted with a renal carcinoma cell line, the overexpression of PAF-AH induced a significant reduction of functional vessel formation.


CONCLUSIONS
These results suggest that inactivation of PAF, produced by TEC, by the overexpression of plasma PAF-AH affects survival, migration, and the angiogenic response of TEC both in vitro and in vivo.
Doublier
Sophie
S
Department of Internal Medicine, Centre for Molecular Biotechnology, University of Turin, Turin, Italy.
Ceretto
Monica
M
Lupia
Enrico
E
Bravo
Stefania
S
Bussolati
Benedetta
B
Camussi
Giovanni
G
D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase / Q000096:biosynthesis* / Q000737:chemistry; D000818:Animals; D023201:CD40 Ligand / Q000096:biosynthesis; D045744:Cell Line, Tumor; D042783:Endothelial Cells / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D051379:Mice; D016513:Mice, SCID; D008954:Models, Biological; D009369:Neoplasms / Q000378:metabolism / Q000473:pathology*; D009389:Neovascularization, Pathologic; D010972:Platelet Activating Factor / Q000737:chemistry; D013917:Thrombin / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
D010972:Platelet Activating Factor; D042461:Vascular Endothelial Growth Factor A; D023201:CD40 Ligand; D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase; D013917:Thrombin