JAG1 and breast cancer: Recently, studies have reported that reduced expression or dysregulation of DLL4 is a key mechanism for Notch‐mediated predisposition to carcinogenesis and tumourigenesis in Li‐Fraumeni syndrome (LFS)17 and the DLL1 and DLL4 ligands are required for maintenance of intestinal progenitor and stem cells (SCs) and are involved in EMT.18, 19 Jagged 1 is highly expressed in metastatic prostate cancer and high expression of Jagged1 in breast cancer is linked to poor survival rates.20, 21 Nevertheless, the mechanism of Jagged1 in cisplatin‐resistant ovarian cancer is still unclear.