PTGS2 and Kaposi's sarcoma: The ability of KSHV to trigger invasiveness and angiogenesis is important for the development of KS and is associated with higher expression of matrix metalloproteinases (MMPs), activation of cyclooxygenase 2 (Cox-2), mitogen-activated protein kinase kinase kinase kinase 4 (MAP4K4), PI3K/Akt/mTOR, NF-κB and PLCγ1 pathways [29,38,55–59].