PECAM1 and neoplasm: Tumor sections were stained for cluster of differentiation 31 (CD31; also known as platelet endothelial cell adhesion molecule 1 or PECAM-1) to detect tumor vasculature by identifying endothelial cells [34] (Fig. 5C,D), for antigen Ki-67 to identify cells undergoing proliferation [35] (Fig. 5C,E), and for γ-H2AX foci to identify degree of DNA damage.