CCR5 and neoplasm: Moreover, histological examination of size matched tumors that were harvested just prior to exponential growth (Day 14), revealed significant angiogenic defects in CCR5 null mice, including reduced vessel branching (P < 0.0001), decreased vascular density (P = 0.0273), and reduced tumor endothelial cell numbers (P = 0.0002) (Figure 2B and Supplementary Tables S3B-S3D).