MVs genetically engineered to express the human carcinoembryonic antigen (CEA) or the human sodium iodide symporter (NIS), both used to track viral gene expression in vivo, showed substantial antitumor activity against glioma cell lines and orthotopic xenografts and have been tested in patients with malignant brain tumors [47,48]. Here, SLC5A5 is linked to central nervous system cancer.