In contrast to the expression of both Flk-1 and Flt-1 in endothelial cells, Flt-1 is widely expressed in many non-endothelial cell types, including hepatocytes, bone marrow progenitor cells, monocytes, macrophages, neural cells, vascular smooth muscle cells, and various tumor cells [16-19]. This evidence concerns the gene FLT1 and neoplasm.