To solidify the role of p53 in Spen ablation–induced tumor vessel normalization, we crossed Cdh5-CreERT2-SPENf mice with p53-floxed (p53fl) mice to obtain Cdh5-CreERT2-SPENfl/fl mice on an endothelial p53+/fl (ep53+/–) background. Here, TP53 is linked to neoplasm.