Fig. 1.
Transcription of CXCR4 and CXCR7 in different tumor and endothelial cells and binding of NIR-fluorescent ligand SDF-1-IRDye 800CW. a Transcription of the chemokine receptors in different cell types as determined by quantitative RT-PCR; ∆CT values to GAPDH (glyceraldehyde-3-phosphate dehydrogenase) are given (∆CT = 3.3 corresponds to one magnitude). CXCR4 and CXCR7 are highly transcribed both in human umbilical vein endothelial cells (HUVEC) and in MCF-7 breast cancer cells; CXCR4 is found at moderate levels in MDA-MB-231 breast cancer cells, but undetectable in glioma and HT29 colon carcinoma cells; CXCR7 is also highly transcribed in glioma cells, but not in MDA-MB-231 and HT29 cells. b Example of NIR-fluorescence labeling of tumor cells by SDF-1-IRDye 800CW. Cultures of different numbers with A 764 glioma cells were exposed for 1 h at 37°C to 100 nM SDF-1-IRDye 800CW or the corresponding albumin (BSA) conjugate and NIR fluorescence visualized with an Odyssey Infrared Imaging system (λEx = 785 nm, λEm = 800 nm). As low as 500 cells can be detected by the specific ligand; the unspecific probe yields no background even with 50,000 cells. c Quantification of the NIR-fluorescence by bound SDF-1-IRDye 800CW and controls on A764 glioma cells: top left, cell number dependency (100 nM, 1 h at 37°C), top right, displacement of bound SDF-1-IRDye 800CW (100 nM) by different concentrations of native SDF-1, CXCL16 (alternate chemokine) and lactalbumin (non-specific control; 1 h at 37°C); bottom left , time-dependency of binding (100 nM, 37°C), bottom right , concentration-dependency of SDF-1-IRDye 800CW-binding compared with EGF-IRDye 800CW (binding to EGFR on the cells) and BSA-IRDye 800CW (non-specifc control; all for 1 h at 37°C)