SLC5A5 and central nervous system cancer: While in these proof-of-principle experimental set-ups ex vivo NIS-transfected glioma cell lines were used, as a next step towards clinical application, we sought to apply and improve upon previously validated methods of systemic non-viral NIS gene delivery using [124I]NaI or [18F]TFB-PET imaging for monitoring of efficacy and tumor selectivity, which will be addressed in the next section.