Bos et al. 3 reported that gene expression analysis of brain metastatic cells and clinical samples identified the genes for cyclooxygenase (COX2, also known as prostaglandin-endoperoxide synthase 2: PTGS2), the epidermal growth factor receptor (EGFR) ligand heparin binding EGF like growth factor (HBEGF), and an a2,6-sialyltransferase (ST6GALNAC5) as mediators of cancer cell passage through the BBB3. This evidence concerns the gene PTGS2 and cancer.