Fluorescence endoscopic detection of murine colitis-associated colon cancer by topically applied enzymatically rapid-activatable probe.
OBJECTIVE
Screening colonoscopy to monitor for early colitis-associated colon cancer (CAC) is difficult due to the aberrant mucosal patterns associated with long-standing colitis. The aim of this study was to develop a rapid fluorescent detection method for use during colonoscopy for improving the detection of CAC utilising a topically applied enzymatically activatable probe (gGlu-HMRG) which fluoresces in the presence of γ-glutamyltranspeptidase (GGT), an enzyme associated with cancer.


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.


CONCLUSIONS
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.
Molecular Imaging Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Building 10, Room B3B69, MSC1088, Bethesda, MD 20892-1088, USA.
Makoto
M
Mitsunaga
Nobuyuki
N
Kosaka
Peter L
PL
Choyke
Matthew R
MR
Young
Christopher R
CR
Dextras
Shakir M
SM
Saud
Nancy H
NH
Colburn
Masayo
M
Sakabe
Tetsuo
T
Nagano
Daisuke
D
Asanuma
Yasuteru
Y
Urano
Hisataka
H
Kobayashi
D000230:Adenocarcinoma / Q000175:diagnosis / Q000201:enzymology / Q000209:etiology; D000287:Administration, Topical; D000818:Animals; D014408:Biomarkers, Tumor / Q000378:metabolism; D001706:Biopsy; D003092:Colitis / Q000150:complications*; D003106:Colon / Q000201:enzymology; D003110:Colonic Neoplasms / Q000175:diagnosis* / Q000201:enzymology / Q000209:etiology*; D003113:Colonoscopy / Q000379:methods; D004195:Disease Models, Animal; D055088:Early Detection of Cancer / Q000379:methods; D005456:Fluorescent Dyes / Q000008:administration & dosage; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence / Q000379:methods; D011230:Precancerous Conditions / Q000175:diagnosis / Q000201:enzymology / Q000209:etiology; D014407:Tumor Cells, Cultured; D005723:gamma-Glutamyltransferase / Q000378:metabolism
D014408:Biomarkers, Tumor; D005456:Fluorescent Dyes; D005723:gamma-Glutamyltransferase