Double knockout of Spen and recombination signal binding protein for immunoglobulin κ J region (Rbpj) (53), the transcription factor mediating Notch signaling, did not rescue the Spen ablation phenotype (Supplemental Figure 8, H and I), suggesting that SPEN deficiency does not normalize tumor vessels by activating Notch. Here, RBPJ is linked to neoplasm.