In vivo diagnosis of epidermal growth factor receptor expression using molecular imaging with a cocktail of optically labeled monoclonal antibodies.
OBJECTIVE
Epidermal growth factor receptors (EGFR) play an important role in tumorigenesis and, therefore, have become targets for new molecular therapies. Here, we use a "cocktail" of optically labeled monoclonal antibodies directed against EGFR-1 (HER1) and EGFR-2 (HER2) to distinguish tumors by their cell surface expression profiles.


METHODS
In vivo imaging experiments were done in tumor-bearing mice following s.c. injection of A431 (overexpressing HER1), NIH3T3/HER2+ (overexpressing HER2), and Balb3T3/DsRed (non-expression control) cell lines. After tumor establishment, a cocktail of optically labeled antibodies: Cy5.5-labeled cetuximab (anti-HER1) and Cy7-labeled trastuzumab (anti-HER2) was i.v. injected. In vivo and ex vivo fluorescence imaging was done. For comparison with radionuclide imaging, experiments were undertaken using (111)Indium-labeled antibodies. Additionally, a "blinded" diagnostic study was done for mice bearing one tumor type.


RESULTS
In vivo spectral fluorescent molecular imaging of 14 mice with three tumor types clearly differentiated tumors using the cocktail of optically labeled antibodies both in vivo and ex vivo. Twenty-four hours after injection, A431 and NIH3T3/HER2+ tumors were detected distinctly by their peak on Cy5.5 and Cy7 spectral images, respectively; radionuclide imaging was unable to clearly distinguish tumors at this time point. In blinded single tumor experiments, investigators were able to correctly diagnose a total of 40 tumors.


CONCLUSIONS
An in vivo imaging technique using an antibody cocktail simultaneously differentiated two tumors expressing distinct EGFRs and enabled an accurate characterization of each subtype.
Barrett
Tristan
T
Molecular Imaging Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Koyama
Yoshinori
Y
Hama
Yukihiro
Y
Ravizzini
Gregory
G
Shin
In Soo
IS
Jang
Beom-Su
BS
Paik
Chang H
CH
Urano
Yasuteru
Y
Choyke
Peter L
PL
Kobayashi
Hisataka
H
D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry; D061067:Antibodies, Monoclonal, Humanized; D002232:Carbocyanines / Q000032:analysis / Q000737:chemistry; D045744:Cell Line, Tumor; D000068818:Cetuximab; D066246:ErbB Receptors / Q000032:analysis*; D005434:Flow Cytometry; D051379:Mice; D008815:Mice, Inbred Strains; D015335:Molecular Probes / Q000032:analysis / Q000737:chemistry; D009369:Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging; D011877:Radionuclide Imaging; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis*; D000068878:Trastuzumab
D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D002232:Carbocyanines; D000068818:Cetuximab; D066246:ErbB Receptors; D015335:Molecular Probes; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab; C098793:CY5.5 cyanine dye; C501744:indotricarbocyanine; C512478:EGFR protein, human