PECAM1 and neoplasm: To gain more insight into the relevance of endothelial Cav1 for growth and radiation response of prostate epithelial tumors, we additionally compared tumor hypoxia and tumor cell proliferation in tumors grown on Cav1-proficient and Cav1-deficient mice on the histological level by using co-immunostaining for endothelial CD31 expression and hypoxia inducible factor 1-alpha (HIF1-alpha) and the proliferation marker Ki67, respectively (Supplementary Figure 2).