Potential of the FES-hERL PET reporter gene system - Basic evaluation for gene therapy monitoring

Purpose: In vivo reporter genes can be powerful tools in supporting and ensuring the success of gene therapy. A careful and rational design of a reporter system is essential to realize a noninvasive in vivo reporter gene imaging system applicable for humans. We designed a new in vivo reporter gene imaging system that uses F-18-labeled estradiol (FES) and human estrogen receptor ligand (hERL) binding domain, taking advantage that FES is a radiopharmaceutical already being used for human studies with access to a wide range of tissues, including the brain, and that hERL lacking DNA binding domain can no longer work as a transcription factor, and carried out basic studies to evaluate its potential for gene therapy monitoring. Methods: We constructed a plasmid (pTIER) to coexpress a model therapeutic gene and the reporter gene hERL and transfected Cos7 cells and examined their uptake of [3H]estradiol and FES in culture media. The uptake of FES by mouse calf muscle electroporated with pTIER was also tested. Results: The cells transfected with pTIER took up the radioligands efficiently and specifically in culture media. Also, the mouse calf muscle electroporated with pTIER accumulated a higher amount of FES than did the control. Conclusion: The data indicate that our new reporter gene system seems promising for in vivo imaging of gene expression and gene therapy monitoring