PECAM1 and neoplasm: However, the fractionated irradiation-induced increase in the SMA+CD31+ population in WT tumours was significantly inhibited in EC-p53KO tumours, whereas pimonidazole-staining intensity and the Ki67+CD44v6+ cancer cell population in hypoxic areas were not different between WT and EC-p53KO tumours (Supplementary Fig. 9e, f).