Undetectable T22-GFP-H6-FdU emitted fluorescence in normal tissues, except for a transient accumulation 5h after a 100μg dose in the liver, which disappears at 24 h. Liver emitted fluorescence is transient and significantly lower than the one registered in tumor tissue. Tumor/Liver ratio= 7.5 (see tumor intensity in Fig 2B, which was registered in the same experiment) (N=5 mice/group). Scale bar, 1 cm. 