Dynamic Fluorescence Imaging of Orally-administered Tumor-targeting Salmonella typhimurium A1-R Expressing Green Fluorescent Protein Trafficking Through the Gastrointestinal System to Target Fibrosarcomas in Nude Mice.

Abstract

Background/aim: Salmonella typhimurium A1-R (A1-R) expresses green fluorescent protein (GFP) and has the ability to selectively target and inhibit all major cancer types in murine models without persistently infecting healthy tissue. A1-R is being developed for tumor targeting by oral administration. The aim of the present study was to demonstrate real-time imaging of orally-administered A1-R in a fibrosarcoma nude-mouse model and to visualize its trafficking through the gastrointestinal system to the tumor and normal organs.

Materials and methods: A1-R-GFP (3.3×10⁸ colony-forming units/ml) was administered orally to HT1080 human fibrosarcoma nude-mouse models which were fasted the day before administration. Fluorescence images of A1-R-GFP inside the gastrointestinal tract at 0, 2 and 4 hours after oral gavage were captured. The number of colonies of A1-R-GFP in tumors and liver were determined at 4 hours, and on days 1, 3 and 4 by growth from homogenized tumor and liver tissue on agar plates.

Results: The trafficking of A1-R-GFP through the murine gastrointestinal tract post-gavage was monitored in real-time via GFP fluorescence imaging. Bacteria, initially observed in the stomach, migrated to the small intestine and the colon and subsequently to the subcutaneously-implanted fibrosarcoma. A1-R-GFP proliferated in the tumors over time. In contrast, A1-R-GFP in the liver diminished over time.

Conclusion: The present study showed the pathway of orally administered A1-R-GFP in the gastrointestinal system and to the tumor and liver. A1-R selectively proliferated continuously in tumors and was cleared from the liver. These results are critical for future clinical trials of orally-administered A1-R-GFP.