In vivo optical imaging of CD13/APN-expression in tumor xenografts.
The metalloexopeptidase CD13/aminopeptidase N (APN) has been shown to be involved in cancer angiogenesis, invasion, and metastasis. Therefore, a CD13/APN-targeted NGR-peptide was labeled with the cyanine dye Cy 5.5 and applied to image tumor xenografts with different APN-expression levels using both planar and tomographic optical imaging methods. In vitro, the peptide-dye conjugate showed a clear binding affinity to APN-positive HT-1080 cells, while negative MCF-7 cells and predosing with the free NGR-peptide revealed little to no fluorescence. In vivo, tumor xenografts (n>or=5) were clearly visualized by two-dimensional (2-D) planar fluorescence reflectance imaging (FRI) and three-dimensional (3-D) fluorescence mediated tomography (FMT) up to 24 h after injection. FMT also allowed us to quantify fluorochrome distribution in deeper tissue sections, showing an average fluorochrome concentration of 306.7+/-54.3 nM Cy 5.5 (HT-1080) and 116.0+/-18.3 nM Cy 5.5 (MCF-7) in the target tissue after 5 h. Competition with the free NGR-peptide resulted in a reduction of fluorochrome concentration in HT-1080 tumor tissue (195.3+/-21.9 nM; 5 h). We thus conclude that NGR-Cy 5.5 combined with novel tomographic optical imaging methods allows us to image and quantify tumor-associated CD13/APN expression noninvasively. This may be a promising strategy for a sensitive evaluation of tumor angiogenesis in vivo.
von Wallbrunn
Angelika
A
University of Münster, Department of Clinical Radiology, Waldeyerster. 1, Haus Rosebach, Münster, Germany NRW 48149.
Waldeck
Jens
J
Höltke
Carsten
C
Zühlsdorf
Michael
M
Mesters
Rolf
R
Heindel
Walter
W
Schäfers
Michael
M
Bremer
Christoph
C
D000230:Adenocarcinoma / Q000175:diagnosis / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D014408:Biomarkers, Tumor / Q000378:metabolism*; D018826:CD13 Antigens / Q000378:metabolism*; D045744:Cell Line, Tumor; D005260:Female; D005354:Fibrosarcoma / Q000175:diagnosis / Q000378:metabolism* / Q000473:pathology; D020869:Gene Expression Profiling / Q000379:methods; D051379:Mice; D008819:Mice, Nude; D008856:Microscopy, Fluorescence / Q000379:methods*; D009363:Neoplasm Proteins / Q000378:metabolism*; D041622:Tomography, Optical / Q000379:methods*
D014408:Biomarkers, Tumor; D009363:Neoplasm Proteins; D018826:CD13 Antigens