PECAM1 and neoplasm: Upon interrogating the degree of intratumor vasculature with vascular markers ERG and CD31, we noted that OS xenografts treated with ETC-159 demonstrated a striking reduction in tumour vasculature both in the degree of IHC staining (Figure 3a,c), and in the resulting vascularity score obtained from double-blinded vessel counts (Figure 3b,d).