To investigate the role of YY1 in tumor ECs in vivo, we generated EC-specific YY1 knockout mice by crossbreeding YY1flox/flox with Cdh5-CreERT2 transgenic mice to create YY1iΔEC(Cdh5-CreERT2; YY1flox/flo) mice14. Here, YY1 is linked to neoplasm.