mSlc5a5/GFP Reporter Cell Line-LL/2 is a polyclonal population which is constructed by transduction of two lentiviruses, one encoding mouse Slc5a5 cDNA and neomycin resistance gene, the other encoding GFP and puromycin resistance gene. It is an ideal positive control for use in iodine uptake and fluorescence assays. In addition, LL/2 cells form tumors post implantation into immunocompromised mice. The in vivo growth of these tumors can be monitored using PET/SPECT imaging. In vivo fluorescent imaging is not recommended due to high background autofluorescence.