Chemotherapy-resistant human AML stem cells home to and engraft within the bone-marrow endosteal region

Acute myelogenous leukemia (AML) is the most common adult leukemia, characterized by the clonal expansion of immature myeloblasts initiating from rare leukemic stem (LS) cells(1-3). To understand the functional properties of human LS cells, we developed a primary human AML xenotransplantation model using newborn nonobese diabetic/severe combined immunodeficient/interleukin (NOD/SCID/IL)2r gamma(null) mice carrying a complete null mutation of the cytokine gamma c upon the SCID background(4). Using this model, we demonstrated that LS cells exclusively recapitulate AML and retain self-renewal capacity in vivo. They home to and engraft within the osteoblast-rich area of the bone marrow, where AML cells are protected from chemotherapy-induced apoptosis. Quiescence of human LS cells may be a mechanism underlying resistance to cell cycle-dependent cytotoxic therapy. Global transcriptional profiling identified LS cell-specific transcripts that are stable through serial transplantation. These results indicate the potential utility of this AML xenograft model in the development of novel therapeutic strategies targeted at LS cells.