NOTCH3 and breast cancer: To determine the expression pattern of Notch3 and STAT5A in breast cancer cell lines, their mRNA levels, and protein levels were examined and showed that in ER-positive breast cancer cell lines (MCF-7 and T47D), Notch3 and STAT5A were both highly expressed compared with that in TNBC cell lines (MDA-MB-231 and BT549) (Fig. 3b and c).