KDR and cancer: However, increasing number of targets is being investigated in clinical trials, such as MUC1 and carcinoembryonic antigen (CEA) overexpressed in various carcinomas, fibroblast activation protein (FAP) targeting cancer associated fibroblasts in the tumor stroma, and vascular endothelial growth factor receptor 2 (VEGFR2) overexpressed in tumor vasculature [23, 53–57].