MMP2 and head and neck cancer: Thus, we investigated the effect of ANXA1 on the expression of genes that are involved in prostaglandin signaling and whose role in head and neck cancer deserves evaluation [41]: EP3 and EP4 and their downstream effectors MMP2 and MMP9. Prostaglandins are lipid mediators of inflammation released in response to different stimuli, including cigarette smoking [64].