To further understand the downstream effects of Notch activation in differentiating BC in response to each NICD we performed immunohistochemical analysis of ALI Day 28 cross-sections from BC infected with either control lentivirus (Lenti-GFP) or lentivirus expressing NICD1, 2, 3 or 4 (Lenti-NICD1-4) for the downstream effectors HEY1 and HEYL, both of which are upregulated at the mRNA level in response to NICD1 and NICD3 expression (Fig. 5B). This evidence concerns the gene HEY1 and breast cancer.