Bone marrow-myofibroblasts, a major component of bone marrow-stroma, are reported to originate from hematopoietic stem cells We show in this paper that non-adherent leukemia blasts can change into myofibroblasts When myeloblasts from two cases of acute myelogenous leukemia with a fusion product comprising mixed lineage leukemia and RNA polymerase II elongation factor, were Cultured long term, their morphology changed to that of myofibroblasts with similar molecular characteristics to the parental myeloblasts The original leukemia blasts, when cultured on the leukemia blast-derived myofibroblasts, grew extensively Leukemia blasts can create their own microenvironment for proliferation (C) 2009 Elsevier Inc. All rights reserved