KDR and breast carcinoma: In part, it might be due to their low prevalence in tumor vasculature, as judged by the low uptake of VEGFR-2 mediated scVEGF/Cy fluorescent tracer in this tumor relative to others, such as those elicited with human U87 MG glioma and MDA-MB-231 breast carcinoma cell lines (data not shown).