The Notch signaling system that contains four Notch receptors (Notch1- Notch4) and five canonical ligands (Dll1, Dll3, Dll4, Jagged1 and Jagged2), plays important roles including carcinogenesis, cancer stem cell renewal, angiogenesis, and chemotherapy resistance in the progression of breast cancer [38]. Here, DLL4 is linked to breast cancer.