JAG1 and breast cancer: Notch is a highly conserved intercellular signalling pathway and has been implicated in tissue fibrosis in various disease conditions such as scleroderma, lung fibrosis, kidney fibrosis, liver fibrosis and cardiac fibrosis.15, 16 Interestingly, Notch ligand jagged1 has been suggested as a direct target of miR‐21 in breast cancer cells.17 However, the direct link between miR‐21 and Notch signalling in the regulation of myocardial fibrosis remains unclear.