CD31 antibody staining for microvascular density. A. Immunohistochemistry showing CD31 as a marker for endothelial cells, and caspase-3 antibody staining for apoptotic cells in the control, and pentastatin-1 at 5 mg/kg and 10 mg/kg as a marker for endothelial cells and blood vessel density. B. Quantification of microvascular density using CD31 antibody. Blood vessels are stained in tumor sections using the CD31 antibody, and endothelial cells quantified by pixel intensity representing the quantity of endothelial cells as a percentage of the control. Three sample tumors for each condition with eight cross sections were quantified. Pentastatin-1 at 5 mg/kg and 10 mg/kg showed a statistically significant 23% and 24% decrease in microvascular density, respectively, from the control at p < 0.05 *. C. Quantification of the mean number of apoptotic cells per frame at 20× magnification for the PBS-treated control, and pentastatin-1 at 5 mg/kg 10 mg/kg. Controls show an average 7 cells/frame, while pentastatin-1 at 5 mg/kg shows 19 cells/frame and pentastatin-1 at 10 mg/kg show an average of 22 cells/frame. Results are statistically significant at p < 0.01**.