JAG1 and cancer: Members of the Notch pathway—namely the transmembrane receptors Notch 1–4 and the transmembrane ligands Delta-like (DLL) 1, 3, 4 and Jagged (Jag) 1, 2 in mammals—also regulate pathological conditions; by mediating cell-to-cell contacts between the cancer cells themselves, and between tumor cells and adjacent cells, they control tumor growth and metastasis.