VEGF and Flk-1 are both expressed in slowly dividing cells. (a) Immunocytochemistry (confocal) for Flk-1 (green) and CD44 (red). Consistent with the results from flow cytometry (Figure 5c), both antigens were co-expressed in slowly dividing cells. Scale bar = 20 μm. (b) Immunocytochemistry as in panel a, showing Hoechst staining of nuclei. Scale bar = 5 μm. (c) Immunocytochemistry for VEGF (green) indicated that it is also expressed in slowly dividing (Vybrant CM-DiI labeled [red]) cells. Scale bar = 20 μm. VEGF, vascular endothelial growth factor.