CXCL12 and head and neck squamous cell carcinoma: Vascular endothelial growth factor A (VEGF-A) [64], stromal cell-derived factor 1 (SDF-1) [65], and platelet-derived growth factor (PDGF) [66,67,68] are examples of such migratory attractants, the latter being assumed to be involved in the migration of hMSCs towards head and neck squamous cell carcinoma (HNSCC) [67].