Expression of thymidine kinase mediated by a novel non-viral delivery system under the control of vascular endothelial growth factor receptor 2 promoter selectively kills human umbilical vein endothelial cells

Figure 4 Immunofluorescence study (× 400) of cultured human endothelial cells. A: Shows positive-stained human endothelial cells with KDR receptor; B: Shows negative-stained human hepatoma cells without KDR receptor.