In vivo imaging of integrin alpha v beta 3 expression using fluorescence-mediated tomography.
OBJECTIVE
Optical imaging would be desirable for cancer diagnostics since it can potentially resolve relevant oncological target structures in vivo. We therefore synthesised an alpha v beta(3) targeted fluorochrome and imaged tumour xenografts with different alpha v beta(3) expression levels using both planar and tomographic optical imaging methods.


METHODS
An alpha v beta(3)-targeted RGD peptide was labelled with a cyanine dye (Cy 5.5). Binding of the optical tracer was tested on M21 melanoma (n=5), HT-1080 fibrosarcoma (n=6) and MCF-7 adenocarcinoma (n=5) cells and their tumour xenografts. All optical imaging studies were performed using two-dimensional planar fluorescence reflectance imaging (FRI) technology and three-dimensional fluorescence-mediated tomography (FMT).


RESULTS
In vitro, the peptide-dye conjugate showed a clear binding affinity to alpha v beta(3)-positive M21 and HT-1080 cells while alpha v beta(3)-negative MCF-7 cells and pre-dosing with the free RGD peptide revealed little to no fluorescence. In vivo, tumour xenografts were clearly visualised by FRI and FMT up to 24 h post injection. FMT allowed quantification of the fluorochrome distribution in deeper tissue sections showing an average fluorochrome concentration of 417.61 +/- 105.82 nM Cy 5.5 (M21), 353.68 +/- 54.02 nM Cy 5.5 (HT-1080) and 262.83 +/- 155.36 nM Cy 5.5 (MCF-7) in the target tissue 60 min after tracer administration. Competition with the free RGD peptide resulted in a reduction in the fluorochrome concentration in M21 tumour tissue (294.35 +/- 84.27 nM).


CONCLUSIONS
RGD-Cy 5.5 combined with novel tomographic optical imaging methods allows non-invasive imaging of tumour-associated alpha v beta(3) expression and may thus be a promising strategy for sensitive evaluation of tumour target expression.
von Wallbrunn
Angelika
A
Department of Clinical Radiology, University of Münster, Albert-Schweitzer-Strasse 33, 48129, Münster, Germany.|Interdisciplinary Center for Clinical Research (IZKF Muenster, FG3), University of Münster, Münster, Germany.
Höltke
Carsten
C
Department of Clinical Radiology, University of Münster, Albert-Schweitzer-Strasse 33, 48129, Münster, Germany.|Departments of Nuclear Medicine and Clinical Radiology, University of Münster, Münster, Germany.
Zühlsdorf
Michael
M
Department of Hematology and Oncology, University of Münster, Münster, Germany.
Heindel
Walter
W
Department of Clinical Radiology, University of Münster, Albert-Schweitzer-Strasse 33, 48129, Münster, Germany.
Schäfers
Michael
M
Interdisciplinary Center for Clinical Research (IZKF Muenster, FG3), University of Münster, Münster, Germany.|Department of Nuclear Medicine, University of Münster, Münster, Germany.|Interdisciplinary Center for Clinical Research (IZKF Muenster, ZPG 4b), University of Münster, Münster, Germany.
Bremer
Christoph
C
Department of Clinical Radiology, University of Münster, Albert-Schweitzer-Strasse 33, 48129, Münster, Germany. bremerc@uni-muenster.de.|Interdisciplinary Center for Clinical Research (IZKF Muenster, FG3), University of Münster, Münster, Germany. bremerc@uni-muenster.de.
D000818:Animals; D002232:Carbocyanines / Q000494:pharmacology; D045744:Cell Line, Tumor; D002469:Cell Separation; D003952:Diagnostic Imaging / Q000379:methods; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D005453:Fluorescence; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000096:biosynthesis*; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D009842:Oligopeptides / Q000378:metabolism; D014054:Tomography / Q000379:methods*
C098793:CY5.5 cyanine dye; D002232:Carbocyanines; D039302:Integrin alphaVbeta3; D009842:Oligopeptides; C047981:arginyl-glycyl-aspartic acid