Juvenile chronic myelogenous leukemia multilineage CD34+ cells: Aberrant growth and differentiation properties

Juvenile chronic myelogenous leukemia (JCML) is a hematologic malignancy of monocyte-macrophage lineage in which leukemic progression is mediated in an autocrine manner by tumor necrosis factor (TNF-alpha), GM-CSF and possibly other growth factors. Cytogenetic data showing involvement of both erythroid and monocyte-macrophage lineages in the JCML leukemic clone, as well as an observed episode of B-lineage lymphoid blast crisis in JCML, has strengthened the thesis for a lymphohematopoietic pluripotent stem cell origin for the disorder. To study this further, JCML CD34(+) cells from bone marrow (BM) or spleen from six newly diagnosed patients were isolated and cultured in clonogenic assays with combinations of recombinant cytokines. Compared to control CD34(+) cells, JCML cells from all patients showed an aberrant growth pattern restricted almost exclusively to the monocyte-macrophage lineage. Most of the clonogenic activity was seen in a subsorted population of CD34(+), HLA-Dr(-) cells. Additionally, an exaggerated growth response to minute doses of GM-CSF that had no effect on control cells was observed with JCML CD34(+) cells. Recloning (''self-renewal'') of JCML CD34(+) cells was also strongly promoted by GM-CSP. JCML colonies also formed spontaneously in the absence of exogenous cytokines but were augmented by GM-CSF, interleukin 1 and TNF-alpha, the latter feature not seen with control CD34(+) cells from normal BM. The abnormal spontaneous growth pattern of CD34(+) JCML cells could be suppressed directly in vitro by anti-TNF-alpha antibodies and anti-GM-CSF antibodies alone or in combination, and by soluble TNF-alpha receptors (sTNF-R:Fc), consistent with the notion that JCML CD34(+) cells are stimulated by both cytokines in an autocrine manner. In malignant CD34(+) cells from one patient, the cytogenetic marker monosomy 7 proved leukemic involvement of monocyte-macrophage, erythroid and B-lymphoid lineages. We conclude that CD34(+) JCML cells of multilineage potential exhibit excessive and aberrant monocyte-macrophage colony formation, a property that was previously observed in JCML progenitors found in light density cell fractions. Thus, within the CD34(+) cellular compartment is a subpopulation of JCML ''stem'' cells that accounts for the abnormal leukemic proliferative activity in this disease.