Abstract
PURPOSE: This study aims to use a simple, quantitative method to compare the HSV1sr39TK/(18) F-FHBG PET reporter gene/PET reporter probe (PRG/PRP) system with PRGs derived from human nucleoside kinases. PROCEDURES: The same adenovirus vector is used to express alternative PRGs. Equal numbers of vectors are injected intravenously into mice. After PRP imaging, quantitative hepatic PET signals are normalized for transduction by measuring hepatic viral genomes. RESULTS: The same adenovirus vector was used to express equivalent amounts of HSV1sr39TK, mutant human thymidine kinase 2 (TK2-DM), and mutant human deoxycytidine kinase (dCK-A100VTM) in mouse liver. HSV1sr39TK expression was measured with (18) F-FHBG, TK2-DM and dCK-A100VTM with (18) F-L-FMAU. TK2-DM/(18) F-L-FMAU and HSV1sr39TK/(18) F-FHBG had equivalent sensitivities; dCK-A100VTM/(18) F-L-FMAU was twice as sensitive as HSV1sr39TK/(18) F-FHBG. CONCLUSIONS: The human PRG/PRP sensitivities are comparable and/or better than HSV1sr39TK/(18) F-FHBG. However, for clinical use, identification of the best PRP substrate for each enzyme, characterization of probe distribution, and consequences of overexpressing nucleoside kinases must be evaluated.