Based on the in vivo observation of TF expression on tumor vascular endothelial cells in breast cancer tissues from patients [4] and some mouse models of human tumor xenografts [5–7], we have begun developing such an approach using tissue factor (TF), a 47-kDa membrane-bound receptor [4, 8–11], as the target molecule on angiogenic VECs. This evidence concerns the gene F3 and neoplasm.