In the context of tumor angiogenesis two reports suggest that tumor cells expressing Jagged1 can act in a pro-angiogenic manner: induction of the Notch ligand Jagged1 by growth factors (via MAPK) in head and neck squamous cell carcinoma was shown to trigger Notch activation in neighboring endothelial cells and promote capillary-like sprout formation [12], and Jagged1 expressed in breast tumor cells can influence tumor angiogenesis [13]. This evidence concerns the gene JAG1 and head and neck squamous cell carcinoma.