A relevant study on hepatocellular carcinoma demonstrated that prostaglandin E2 (PGE2) activates prostaglandin EP3 receptor (PTGER3) in the mesenchymal cells surrounding tumor cells, thereby promoting the activation and release of vascular endothelial growth factor, MMP-2 and MMP-9; in this manner, PGE2 ultimately promotes angiogenesis and tumor cell growth (29). The gene discussed is MMP9; the disease is hepatocellular carcinoma.