Further, in order to directly demonstrate that BM blasts of MDS patients actually express Ang-1 protein, we prospectively sorted CD34+ cells from BM mononuclear cells by fluorescence activated cell sorter (FACSAria; BD Bioscience, San Jose, CA, USA) in two patients diagnosed as having RA with excess blasts and then performed immunocytochemical staining of these sorted CD34+ cells by immunoperoxidase technique. Here, CD34 is linked to myelodysplastic syndrome.