In vivo near-infrared fluorescence imaging of carcinoembryonic antigen-expressing tumor cells in mice.
OBJECTIVE
To prospectively depict carcinoembryonic antigen (CEA)-expressing tumors in mice with a high-affinity probe consisting of a near-infrared (NIR) fluorochrome and the clinically used anti-CEA antibody fragment arcitumomab.


METHODS
This study was approved by the regional animal committee. By coupling a NIR fluorescent (NIRF) cyanine dye (DY-676) to a specific antibody fragment directed against CEA (arcitumomab) and a nonspecific IgG Fab fragment, a bio-optical high-affinity fluorescent probe (anti-CEA-DY-676) and a low-affinity fluorescent probe (FabIgG-DY-676) were designed. The dye-to-protein ratios were determined, and both probes were tested for NIRF imaging in vitro on CEA-expressing LS-174T human colonic adenocarcinoma cells and CEA-nonexpressing A-375 human melanoma cells by using a bio-optical NIR small-animal imager. In vivo data of xenografted LS-174T and A-375 tumors in mice (n = 10) were recorded and statistically analyzed (Student t test).


RESULTS
The dye-to-protein ratios were determined as 3.0-3.5 for both probes. In vitro experiments revealed the specific binding of the anti-CEA-DY-676 probe on CEA-expressing cells as compared with CEA-nonexpressing cells; the FabIgG-DY-676 probe showed a markedly lower binding affinity to cells. In vivo LS-174T tumors xenografted in all mice could be significantly distinguished from A-375 tumors with application of the anti-CEA-DY-676 but not with that of the FabIgG-DY-676 at different times (2-24 hours, P < .005) after intravenous injection of the probes. Semiquantitative analysis revealed maximal fluorescence signals of anti-CEA-DY-676 to CEA-expressing tumors about 8 hours after injection.


CONCLUSIONS
Findings of this study indicate the potential use of the high-affinity probe anti-CEA-DY-676 for specific NIRF imaging in in vivo tumor diagnosis.
Lisy
Marcus-René
MR
Institute for Diagnostic and Interventional Radiology, Friedrich-Schiller-University Jena, FZL Erlanger Allee 101, D-07747 Jena, Germany.
Goermar
Annika
A
Thomas
Claudia
C
Pauli
Jutta
J
Resch-Genger
Ute
U
Kaiser
Werner A
WA
Hilger
Ingrid
I
D000230:Adenocarcinoma / Q000378:metabolism*; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry*; D002232:Carbocyanines / Q000737:chemistry*; D002272:Carcinoembryonic Antigen / Q000378:metabolism*; D003110:Colonic Neoplasms / Q000378:metabolism*; D005260:Female; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry*; D051379:Mice; D008807:Mice, Inbred BALB C; D016133:Polymerase Chain Reaction; D011446:Prospective Studies; D013050:Spectrometry, Fluorescence; D013055:Spectrophotometry, Infrared; D051598:Whole Body Imaging
D000911:Antibodies, Monoclonal; D002232:Carbocyanines; D002272:Carcinoembryonic Antigen; D007140:Immunoglobulin Fab Fragments