Effect of 5-fluorouracil on tumor vasculature in MCF-7 xenografts. The number of total (CD31+) and functional (DiOC7+) blood vessels per tumor area (left panels), and the percentage of functional blood vessels (right panels) present on Day 0, 2, 4, 8, and 12 in MCF-7 A) subcutaneous xenografts or B) orthotopic xenografts following a single dose of 5-fluorouracil, 5-FU (100 mg/kg, administered intraperitoneally). C) The number of total (CD31+) and functional (DiOC7+) blood vessels (per tumor area), and the percentage of functional blood vessels present in Day 12 MCF-7 subcutaneous or orthotopic xenografts. Bars represent the mean of 2-6 tumors; error bars represent standard error of the mean (SEM). Symbols represent statistical significance for functional and percent functional (+) blood vessels as compared to control (Day 0) tumors, and significance between subcutaneous and orthotopic tumors.