ABERRANT GROWTH OF GRANULOCYTE-MACROPHAGE PROGENITORS IN JUVENILE CHRONIC MYELOGENOUS LEUKEMIA IN SERUM-FREE CULTURE

We investigated the properties of granulocyte-macrophage (GM) progenit ors obtained from patients with juvenile chronic myelogenous leukemia (JCML). CD34(+) bone marrow cells from a patient with JCML, unlike nor mal bone marrow cells, generated a large number of cells in serum-cont aining liquid culture without additional hematopoietic factors. In ser um-deprived culture, only granulocyte colony-stimulating factor (G-CSF ) had a modest stimulatory effect on GM colony growth in normal contro ls. In contrast, stem cell factor (SCF), granulocyte-macrophage colony -stimulating factor (GM-CSF), and interleukin-3 (IL-3), as well as G-C SF, when tested individually, generated significant numbers of GM colo nies in some JCML patients. All two-factor combinations generated sign ificantly more GM colonies in JCML compared with normal controls. In p articular, GM-CSF plus SCF exerted an interaction equivalent to the al l-factor combination in most patients. Significant differences in the size and constituent cells of GM colonies stimulated by GM-CSF plus SC F were also observed. These results suggest that one possible mechanis m for the excessive cell production in JCML is the strong proliferatio n of GM progenitors induced by hematopoietic factors, especially SCF. According to immunofluorescent analysis, however, it is unlikely that this multiplication is due to an increase in the cell surface expressi on of c-kit receptors on JCML progenitors.