Clinical investigation from Mittal et al. (2009) has provided us with evidence on the presence and expression of the Notch proteins (Notch-1, -2, and -4) and their cognate ligands (Jagged-1, Jagged-2, Delta-like ligand 1, and Delta-like ligand 4) in breast cancer in comparison to normal tissue. Here, JAG1 is linked to breast cancer.