[Show abstract][Hide abstract] ABSTRACT: 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.
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.
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.
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.
Preview · Article · Nov 2007 · Clinical Cancer Research
[Show abstract][Hide abstract] ABSTRACT: In this study, we found that Kaposi's sarcoma cells but not human microvascular endothelial cells expressed PAX2, a gene coding for a transcription factor involved both in organogenesis and tumorigenesis. Moreover, Pax2 was frequently expressed, on spindle-shaped cells, in Kaposi's sarcoma lesions. We cloned PAX2 from Kaposi's sarcoma cells and obtained antisense and sense DNA. Transfection of Kaposi's sarcoma cells with antisense DNA, which suppressed Pax2 protein expression, reduced cell growth and survival and enhanced the sensitivity of Kaposi's sarcoma cells to apoptosis induced by serum deprivation or vincristine treatment. In addition, antisense transfection inhibited the cell motility, the invasion of Matrigel, and the spindle shape morphology, which are characteristics of Kaposi's sarcoma cells. Moreover, the alphavbeta3 integrin, known to be involved in tumor invasion, was down-regulated. To evaluate the possible role of Pax2 expression in the endothelial origin of Kaposi's sarcoma cells, human microvascular endothelial cells were transfected with sense DNA. Endothelial cells transfected with sense PAX2 acquired spindle shape morphology, showed enhanced motility and Matrigel invasion, and displayed an enhanced expression of alphavbeta3 integrin. In conclusion, the expression of Pax2 by Kaposi's sarcoma cells correlated with an enhanced resistance against apoptotic signals and with the proinvasive phenotype. Moreover, PAX2-transfected endothelial cells acquired a phenotype resembling that of Kaposi's lesional cells, suggesting a role of this embryonic gene in tumorigenesis.
No preview · Article · Mar 2004 · Journal of Biological Chemistry