Multilineage outgrowth of both malignant and normal hemopoietic progenitor cells from individual chronic myeloid leukemia patients in immunodeficient mice

In this study the ability of malignant and normal progenitors in peripheral blood (PB) and bone marrow (BM) of CML patients in chronic phase to proliferate and produce mature progeny after transplantation into hereditary immunodeficient (SCID and NOD/SCID) mice was examined. Engraftment in NOD/SCID mice preconditioned by total body irradiation (TBI) alone was 10-fold higher than in SCID mice preconditioned by macrophage depletion and TBI, demonstrating that NOD/SCID mice are more suitable for engraftment of chronic phase CML cells. Low-density cells at cell doses of 10-30 x 10(6) and purified CD34(+) cells at doses of approximately 0.2 x 10(6) engrafted NOD/SCID mice, with levels of 2 to 20% CD45(+) cells with production of monocytes, granulocytes, erythroid cells, B-lymphocytes, CD34(+) cells and variable frequencies of erythroid and myeloid colony-forming cells. As demonstrated by fluorescent in site hybridization (FISH) analysis, purified human myeloid, B-lymphoid, erythroid and CD34(+) cells from chimeric mouse BM contained Philadelphia-chromosome (Ph)-positive cells and Ph- cells in similar frequencies as primary cells from the CML patients. These results demonstrate that production of mature normal as well as malignant cells of multiple lineages were supported with similar efficiency. In contrast, all human erythroid and myeloid clonogenic cells detected in the mice were Ph-, which can be attributed to less efficient maintenance or more rapid differentiation of immature Ph+ cells in the mouse microenvironment. CML blast crisis cells also grew well in NOD/SCID mice, with 80-90% of human cells produced containing the Ph-chromosome. The availability of an in vivo assay that supports outgrowth of normal and malignant stem cells from chronic phase and blast crisis CML patients will facilitate examination of differential effects of growth factors, inhibitory cytokines and cytotoxic drugs on survival of normal and malignant stem cells in vivo and on progression of chronic phase CML towards blast crisis.