Three genes have been identified to mediate the transmigration of breast cancer cells across the BBB: the α2, 6-sialyltransferase (ST6GALNAC5), heparin-binding epidermal growth factor-like growth factor (HB-EGFHB-EGF) and cyclooxygenase-2 (COX2). The gene discussed is PTGS2; the disease is breast cancer.