Development of Bio-imaging Mouse Model for Efficacy of New Drug Candidates

Laboratory animals more than 100 million have consumed annually in laboratories for test of chemicals, medical devices, drugs and foods, and also have brought about a social problem in aspect of bioethics. Recently, bio-imaging system that can detect the fluorescence or bioluminescence signals in vivo, has considered as a replacement solution in the use of laboratory animals. Here, we tried to construct a mouse model with BRET(Bioluminescence Resonance Energy Transfer) system that is programmed to cut a recognizable site (DEVD amino acid sequence) by caspase-3 when the drug efficacy is observed. BRET expression vector was composed of a bioluminescent luciferase and a red fluorescent protein (tdTomato) under CAG promoter, and DEVD sequence was inserted between their proteins. Luciferase and tdTomato expressed normally in BRET-PC3 human prostatic cancer cells, and red fluorescence was observed under radiation- free status. During drug inducible apoptosis, bioluminescence rate catalyzed by luciferase rapidly increased whereas red fluorescent intensity decreased slightly. Next, BRET-PC3 cells injected into underskin in the femoral region to produce xenograft mouse model and were identified successfully expectable events occurred after treatment of apoptotic drugs like as BRET-PC3 cells. Finally, we constructed mouse expressing BRET system by microinjection and confirmed strong detectable signals using bio-imaging equipment. In this study, we developed a new mouse model with BRET system that can detect apoptotic reagents, and suggest the possibility as a teat model for drug discovery and development.