YY1 and neoplasm: To identify the role of endothelial YY1 in tumor angiogenesis and tumor growth, we generated tamoxifen-inducible EC-specific YY1-deficient (YY1iΔEC) mice for genetic ablation YY1 in ECs, and we found that EC-specific YY1 knockout in mice greatly diminished tumor angiogenesis and tumor growth in vivo.