A subpopulation of the Ph+ B-ALL cell line SUP-B15 presents leukemia stem cells (LSCs) and expresses stem cell markers (CD34, CD38, and c-Kit) and endothelial antigens (Flk-1 and PECAM-1); moreover, LSCs express VE-cadherin after a long-term co-culture on stromal cells (97). The gene discussed is PECAM1; the disease is acute lymphoblastic leukemia.