Treatment with GU81 either alone or in combination with doxorubicin reduces total vascular area and vessel size in the MMTV-PyMT model. Tumor sections from each group were evaluated for various vascular parameters following staining with the endothelial cell marker endomucin. Representative images from each treatment group are displayed in (A). (B) The number of vessels per 200× field was evaluated using Nikon Elements software and is displayed as the mean +/- SEM. All quantification includes 3 animals/group and 5 sections/animal. (C) The total vascular area was calculated using Nikon Elements software and is displayed as the percent fluorescent area per 200× field. (D) The percent fluorescent area was divided by the total vessel number for each section in order to obtain a relative vessel size. *, p < 0.05; **, p < 0.01 vs control; ***, p < 0.001, t-test.