PTGS2 and neoplasm: Among the cellular genes regulated by MAP4K4 silencing in KSHV-infected endothelial cells were three that have previously been reported to contribute to the invasive phenotype of tumour cells: PTGS2, encoding cyclooxygenase 2 (COX-2), and the genes coding for matrix metalloproteinases 7 and 13 (MMP-7 and MMP-13) (figure 4A).