Gamma camera and optical imaging with a fusion reporter gene using human sodium/iodide symporter and monomeric red fluorescent protein in mouse model

Purpose: Multimodality imaging contributes to the activation of translational research by compensating for its weak points. Herein, we developed a noninvasive dual-reporter gene system for nuclear and optical imaging. Materials and methods: We constructed a fusion reporter vector concurrently expressing the human sodium/iodide symporter (hNIS) and monomeric red fluorescent protein (mCherry), and evaluated the function of this fusion reporter system under in vitro and in vivo conditions. Results: The expression of hNIS/mCherry fusion gene was confirmed in transfected cells using reverse transcription polymerase chain reaction (RT-PCR) and Western blotting. As the numbers of cells increased, the fluorescence and ¹²⁵I uptake increased in the hNIS/mCherry-transfected cells, and a high correlation between fluorescence intensity and radioactivity was noted. The fluorescence intensities and radioactivity signals were also well-correlated in HT-29-hNIS/mCherry tumors (R ² = 0.9304) in in vivo fluorescence and gamma camera imaging. Conclusions: The dual-reporter imaging method using hNIS and mCherry genes reflected tumor extent as well as viable cell numbers, and correlated well with one another. This suggests that the hNIS/mCherry dual-reporter system can be a useful tool for multi-modal imaging.