KDR and head and neck squamous cell carcinoma: Periostin has previously been shown to promote angiogenesis, as demonstrated by several findings: (i) periostin enhances VEGF receptor Flk-1/KDR expression in endothelial cells through an integrin αvβ3-FAK-mediated signaling pathway [13], (ii) recombinant periostin enhances capillary formation [12], and (iii) increased expression of periostin is correlated with the number of blood vessels and with metastasis in HNSCC [14].