NOTCH1 and breast cancer: To determine the relevance of our findings in tissue culture to the downregulation of PTEN that is observed in human breast tumor surgical samples, we examined the large TCGA data cohort containing mRNA and protein expression data and found that cases expressing high levels of EZH2 (RNA-seq z-score >1, about 15% of all breast cancers and 57% of TNBCs) tend to have increased expression of NOTCH1 and decreased expression of PTEN at both the transcript and protein levels30,31,34 (Fig. 4h).