Application of MRI and Bioluminescence Dual Reporter Gene Imaging for In Vivo Monitoring of Tumor Growth

Objective: This study aimed to explore the mechanism underlying colorectal cancer occurrence and development using magnetic resonance imaging (MRI) and bioluminescence dual reporter gene imaging. Materials and Methods: Human colorectal cancer LoVo cells were infected with Ad-transferrin receptor (TFRC)-luciferase adenovirus. Luciferase expression in LoVo cells was detected by bioluminescence imaging in vitro. The expression of TFRC gene in LoVo cells was detected and analyzed by real-time fluorescence quantitative polymerase chain reaction (qPCR). The cellular toxicity was determined using a cell counting kit-8 (CCK-8) assay. The adenovirus with the reporter gene was labeled using transferrin-conjugated ultrasmall superparamagnetic iron oxide (Tf-USPIO) in vitro. The double-labeled LoVo cells were scanned using 7.0-T T2W MRI, T-2 map, and T-2* map sequences to analyze the signal intensity. The LoVo colorectal tumor model was established by subcutaneously injecting 1 x 10(7) double-reporter gene-labeled LoVo cells into the groin area of BALB/c mice. Intravenous Tf-USPIO, molecular MRI, and bioluminescence imaging were used to monitor tumor growth and development, followed by Prussian blue staining. Results: The qPCR data indicated significant overexpression of TFRC reporter gene in LoVo cells transfected with Ad-TFRC-luciferase. The CCK-8 assay showed that dual reporter gene expression marked by Ad-TFRC-luciferase had no adverse effects on cell proliferation or viability. In vitro, the signal intensity of LoVo cells labeled with USPIO decreased. In vivo, the hypointense regions with tumor cells enlarged dramatically over time. Prussian blue staining showed iron aggregation in the tumor tissue. Conclusion: MRI and bioluminescence dual reporter gene imaging system can help monitor tumor growth and development.