NOTCH1 and breast cancer: To investigate the possible role of the Notch signaling pathway in initiation of the EMT process in breast cancer cells, we first explored the expression levels of the NICD of Notch1 (N1ICD) and its ligand Jagged1 in five human breast cancer cell lines, human mammary epithelial cells (HMECs), and non-tumorigenic MCF-10A cells.