Therefore, they suggested a mechanism whereby Notch is activated in aggressive and poor-prognosis breast tumours (since JAG1 is a ligand of Notch-receptor-1) and that the basal breast cancer subgroup (belonging to ER-negative BC) shows poor overall survival as a result of JAG1-induced Notch activation in some of these tumours. This evidence concerns the gene NOTCH1 and breast carcinoma.