Conclusion
These results suggest that gGlu-HMRG can improve endoscopic detection of CAC with a higher target to background ratio than conventional white light colonoscopy. This could be of benefit to patients with long-standing colitis who must undergo repeated screening colonoscopies.
Methods
Expression of GGT in colon cell lines was examined with fluorescence microscopy and flow cytometry. A mouse model (azoxymethane/dextran sulphate sodium) of CAC was used and mice were examined with white light and fluorescence colonoscopy before and after topical gGlu-HMRG administration.
Results
Expression of GGT, although variable, was higher in human colon cancer cells than normal human colon cells. Using fluorescence colonoscopy in mice, gGlu-HMRG fluorescent lesions were detected 5 min after topical administration and fluorescence persisted for at least 30 min. Fluorescence guided biopsy revealed all fluorescent lesions that contained cancer or dysplasia (n=16), whereas three out of 12 non-fluorescent lesions contained low grade dysplasia and others did not contain neoplastic histology. Microscopic inflammatory infiltration also had variable fluorescence but in general was much lower (∼10-fold) in signal than cancer. Repeat fluorescence endoscopy allowed individual tumours to be monitored.