TNF-α treatment mediated vascular pre-conditioning events. (A) TNF-α induced histological changes in tumor tissue including congestion/thrombosis, inflammatory infiltrate and hemorrhage (scale bar = 100 μm). (B) TNF-α resulted in microvascular dilatation and enhanced leukocyte association with vessel walls, as visualized by intravital fluorescent videotaping after intravenous administration of the nuclear dye rhodamine 6G (scale bar = 100 μm). (C) TNF-α induced caspase activation in tumor and endothelial cells at 4 hours after treatment (*, p<0.05), and NFκB activation in endothelial cells at 4 hours and day 1 after treatment (*, p<0.05). Data are presented as the mean (bar height = 1 standard deviation) of three to four independent experiments for each treatment.