NOTCH4 and head and neck neoplasm: For example, NOTCH4, a receptor for the Notch pathway that has been shown to inhibit angiogenesis [50], was elevated in the pauci cellular fibrotic stroma cluster when compared to the higher cellularity stroma, while JAG1, a Notch ligand shown to induce angiogenesis in some head and neck tumors [51], was elevated in highly cellular stroma compared to pauci cellular fibrotic stroma.