ABSTRACT
Transforming growth factor-ß (TGF-ß) triggers apoptosis in endothelial cells, while the mechanisms underlying this action are not entirely understood. Using genetic and pharmacological tools, we demonstrated that TGF-ß induced a moderate apoptotic response in human cultured endothelial cells, which was dependent upon upregulation of the Nox4 NADPH oxidase and production of reactive oxygen species (ROS). In contrast, we showed that ectopic expression of Nox4 via viral vectors (vNox4) produced an antiapoptotic effect. TGF-ß caused ROS-dependent p38 activation, whereas inhibition of p38 blunted TGF-ß-induced apoptosis. However, vNox4, but not TGF-ß, activated Akt, and inhibition of Akt attenuated the antiapoptotic effect of vNox4. Akt activation induced by vNox4 was accompanied by inactivation of the protein tyrosine phosphatase-1B (PTP1B) function and enhanced vascular endothelial growth factor receptor (VEGFR)-2 phosphorylation. Moreover, we showed that TGF-ß enhanced Notch signaling and increased expression of the arterial marker EphrinB2 in a redox-dependent manner. In summary, our results suggest that Nox4 and ROS have pivotal roles in mediating TGF-ß-induced endothelial apoptosis and phenotype specification. Redox mechanisms may influence endothelial cell functions by modulating p38, PTP1B/VEGFR/Akt and Notch signaling pathways.
Subject(s)
Apoptosis , Endothelial Cells/cytology , Human Umbilical Vein Endothelial Cells/cytology , Human Umbilical Vein Endothelial Cells/enzymology , NADPH Oxidases/metabolism , Signal Transduction , Transforming Growth Factor beta1/metabolism , Endothelial Cells/metabolism , Human Umbilical Vein Endothelial Cells/metabolism , Humans , NADPH Oxidase 4 , NADPH Oxidases/genetics , Phenotype , Proto-Oncogene Proteins c-akt/genetics , Proto-Oncogene Proteins c-akt/metabolism , Reactive Oxygen Species/metabolismABSTRACT
PURPOSE: To assess the role of biomarker levels in predicting radiotherapy (RT) response in patients with squamous cell carcinoma of buccal mucosa treated with postoperative RT. MATERIALS AND METHODS: Thirty-one patients with squamous cell carcinoma of buccal mucosa who received postoperative RT were enrolled for the study. Glutathione S-transferase (GST), glutathione reductase (GR), superoxide dismutase (SOD) and catalase activity were analysed from primary tumour and adjacent normal mucosa of the same patients before RT. p53 and p21ras were localized immunohistochemically. RESULTS: Enzyme activation was predicted by comparing the levels of these enzymes in tumour and adjacent normal mucosa. Deactivation of GST, activation of GR, SOD and catalase were associated with poor response to RT. p53 immunoreactivity was associated with failure to respond to RT. CONCLUSIONS: These markers may be useful in predicting treatment outcome in patients receiving postoperative RT, although this conclusion requires confirmation in a larger group of patients.
