PTGS2 and neoplasm: Regarding the overexpression level of COX-2 in most HNSCC tumour tissues, PGE2 was shown to induce “inside-out” integrin signalling through fibronectin (FN) ligand, α5β1 integrin and FAK activation toward tumour progression of EMT, migration and invasion30, while “outside-in” integrin signalling through FN, α5β1 integrin and FAK phosphorylation can induce COX-2 overexpression and PGE2 synthesis toward anti-apoptosis and tumour proliferation31.