NOTCH3 and breast cancer: The WT N3ICD, the phosphodeficient (SA) mutant, or the phosphomimicking (SE) mutant were transiently overexpressed in MCF-7 and T47D luminal A breast cancer cells as well as in the derivatives of MCF-7 cells, in which the NOTCH3 or CSL genes had been knocked out by the CRISPR/Cas9 technique (Fig. S1).