Fig. 2

Image gallery after isolation, cytomorphological analysis and detection of cytokeratin-positive tumor cells (CK+, red staining) and vascular endothelial growth factor expression (VEGFR, blue staining). Top row shows HT29 cell tumor line used as a positive control for VEGFR expression. Middle (patient 1) and bottom (patient 2) rows show an example of heterogeneous expression of VEGFR in two different patients: patient 1 shows positive VEGFR expression in a CTC and patient 2 shows negative VEGFR expression in another CTC. VEGFR-specific immunofluorescence (IF) CTCs were determined with Alexa Fluor^® 350