OBJECTIVE: The herpes simplex virus thymidine kinase (HSVtk) gene has frequently been applied as a reporter gene for monitoring transgene expression in animal models. In clinical gene therapy protocols, however, extremely low expression levels of the transferred gene are generally observed. Consequently, sensitive and selective radiotracers for imaging are required. This study describes the in-vitro evaluation of 2'-[18F]fluoro-5-ethyl-1-beta-D-arabinofuranosyluracil (18F-FEAU) as a candidate tracer for HSVtk imaging with positron emission tomography (PET). METHODS: In cellular accumulation experiments, the potential of 18F-FEAU as a PET tracer for HSVtk was compared to the known acyclic guanosine derivatives 9-[(3-[18F]fluoro-1-hydroxy-2-propoxy)methyl]guanine (18F-FHPG) and 9-[4-[18F]fluoro-3-(hydroxymethyl)butyl]guanine (18F-FHBG), and the thymidine derivatives 3'-deoxy-3'-[18F]fluorothymidine (18F-FLT), 2'-deoxy-2'-[18F]fluoro-5-methyl-1-beta-D-arabinofuranosyluracil (18F-FMAU) and 2'-deoxy-2'-[18F]fluoro-5-iodo-1-beta-D-arabinofuranosyluracil (18F-FIAU). For this purpose, C6 control cells and HSVtk-expressing C6tk cells were incubated with the different tracers for various periods of time and cellular uptake and initial uptake rates were analysed. The initial rate of tracer uptake was determined from the slope of the plot of tracer uptake versus incubation time. RESULTS: After 2 h of tracer incubation, the C6tk/C6 accumulation ratio was 1.6 for 18F-FLT, 2.4 for F-FMAU, 5.5 for 18F-FHPG, 10.3 for 18F-FIAU, 40.8 for 18F-FHBG and 84.5 for 18F-FEAU. The initial tracer uptake rate in C6tk cells was in the order FLT>FMAU>FEAU>FIAU>FHBG>FHPG, whereas the initial tracer uptake rate in C6 control cells was FLT>FMAU>FIAU>FEAU approximately = FHBG approximately = FHPG. The highest HSVtk specific uptake was observed for FEAU. CONCLUSION: This study indicates that the high uptake rate of FEAU together with its high selectivity make this tracer an excellent candidate as a PET tracer for HSVtk gene expression.
OBJECTIVE: The herpes simplex virus thymidine kinase (HSVtk) gene has frequently been applied as a reporter gene for monitoring transgene expression in animal models. In clinical gene therapy protocols, however, extremely low expression levels of the transferred gene are generally observed. Consequently, sensitive and selective radiotracers for imaging are required. This study describes the in-vitro evaluation of 2'-[18F]fluoro-5-ethyl-1-beta-D-arabinofuranosyluracil (18F-FEAU) as a candidate tracer for HSVtk imaging with positron emission tomography (PET). METHODS: In cellular accumulation experiments, the potential of 18F-FEAU as a PET tracer for HSVtk was compared to the known acyclic guanosine derivatives 9-[(3-[18F]fluoro-1-hydroxy-2-propoxy)methyl]guanine (18F-FHPG) and 9-[4-[18F]fluoro-3-(hydroxymethyl)butyl]guanine (18F-FHBG), and the thymidine derivatives 3'-deoxy-3'-[18F]fluorothymidine (18F-FLT), 2'-deoxy-2'-[18F]fluoro-5-methyl-1-beta-D-arabinofuranosyluracil (18F-FMAU) and 2'-deoxy-2'-[18F]fluoro-5-iodo-1-beta-D-arabinofuranosyluracil (18F-FIAU). For this purpose, C6 control cells and HSVtk-expressing C6tk cells were incubated with the different tracers for various periods of time and cellular uptake and initial uptake rates were analysed. The initial rate of tracer uptake was determined from the slope of the plot of tracer uptake versus incubation time. RESULTS: After 2 h of tracer incubation, the C6tk/C6 accumulation ratio was 1.6 for 18F-FLT, 2.4 for F-FMAU, 5.5 for 18F-FHPG, 10.3 for 18F-FIAU, 40.8 for 18F-FHBG and 84.5 for 18F-FEAU. The initial tracer uptake rate in C6tk cells was in the order FLT>FMAU>FEAU>FIAU>FHBG>FHPG, whereas the initial tracer uptake rate in C6 control cells was FLT>FMAU>FIAU>FEAU approximately = FHBG approximately = FHPG. The highest HSVtk specific uptake was observed for FEAU. CONCLUSION: This study indicates that the high uptake rate of FEAU together with its high selectivity make this tracer an excellent candidate as a PET tracer for HSVtk gene expression.
Authors: Hanwen Zhang; Melchor V Cantorias; NagaVaraKishore Pillarsetty; Eva M Burnazi; Shangde Cai; Jason S Lewis Journal: Nucl Med Biol Date: 2012-07-18 Impact factor: 2.408
Authors: Christian T Farrar; Jason S Buhrman; Guanshu Liu; Anne Kleijn; Martine L M Lamfers; Michael T McMahon; Assaf A Gilad; Giulia Fulci Journal: Radiology Date: 2015-02-13 Impact factor: 11.105
Authors: Kim A Muñoz-Álvarez; Jennifer Altomonte; Iina Laitinen; Sibylle Ziegler; Katja Steiger; Irene Esposito; Roland M Schmid; Oliver Ebert Journal: Mol Ther Date: 2015-01-22 Impact factor: 11.454
Authors: Nadimpalli Ravi S Varma; Branislava Janic; A S M Iskander; Adarsh Shankar; Mohammed P I Bhuiyan; Hamid Soltanian-Zadeh; Quan Jiang; Kenneth Barton; Meser M Ali; Ali S Arbab Journal: PLoS One Date: 2012-01-20 Impact factor: 3.240