Transmigration of tumor cells through the BBB is mediated by the upregulation of three genes: (HBEGF (Heparin-Binding Epidermal growth factor-like Growth Factor), COX-2 (PTGS2, Prostaglandin-Endoperoxide-Synthase-2), and ST6GALNAC5 (ST6-N-Acetylgalactosaminide-Alpha-2,6-Sialyltransferase-5)). The gene discussed is PTGS2; the disease is neoplasm.