Engraftment of NOD/SCIDγc^null Mice with Multilineage Neoplastic Cells from Patients with Juvenile Myelomonocytic Leukemia.

Jevenile myelomonocytic leukemia (JMML) is a rare myeloproferative disorder of early childhood, arising from pluripotent stem cells. Previous studies indicate the clonal nature of JMML, involving myeloid, erythroid, megakaryocyte and B-lymphoid lineage. However, it is unclear whether T lymphocyte lineage is involved or not. In one previous report, a patient with JMML and cytogenetic evidence of monosomy 7, a combination of fluorescence activated cell sorting and fluorescence in situ hybridization (FISH) analysis confirmed no T cell lineage involvement. One explanation of sparing T cell lymphocyte involvement in JMML is that the majority of T-lymphocytes are long-lived and borne before the occurrence of the disease. We demonstrated that cells from six patients of JMML repopurate in NOD/SCIDγc^null mice and differenciate into granulocyte, monocyte, erythroid, B-lymphocyte, T-lymphocyte and natural killer(NK) cells. The diagnosis of JMML was based on the internationally accepted criteria. 0.01 to 1×10⁷mononuclear cells were injected through the tail vein of five week old NOD/SCIDγc^null mice. 12 week after transplantation mice were sacrificed and the cells are collected from the femoral bone and spleen and subjected to flow cytometry. The percentage of human CD45 antigen positive cells ranged from 41 to 73%. To examine the involvement of lymphocyte subpopulations, we purified human CD3+,CD19+and CD56+ cells from a murine bone marrow and spleen cells transplanted from a patient with monosomy 7. The purity of cells were more than 95%. The percentage of monosomy 7 cells determined by FISH analysis ranged from 96 to 100% in purified CD3+, CD19+and CD56+ cells. These findings support the concept that JMML originate in transplantable multilineage hematopoietic stem cells. This novel murine xenotransplant model should be useful to investigate the nature of stem cells and test new therapies for patients with JMML.