Blasts from patients with acute myelogenous leukemia express functional receptors for stem cell factor

Abstract

Stem cell factor (SCF) acts in concert with lineage-specific growth factors to stimulate the growth of hematopoietic colonies. To determine if neoplastic human hematopoietic cells would also respond to SCF, we cultured marrow mononuclear cells from 20 patients with newly diagnosed acute myelogenous leukemia (AML) and two normal donors with SCF, interleukin 3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), or combinations of growth factors in semisolid medium, and assessed colony growth. SCF receptors (c-kit receptors) were quantitated by equilibrium binding studies with 125I-SCF, and binding parameters were estimated using the ligand program. The cellular distribution of c-kit receptors was determined by autoradiography. Our results show that SCF alone or in combination with IL-3 or GM-CSF increased both the number and size of colonies in 10 of the patients. Receptors for SCF were identified on the blasts from all 20 AML patients. The number of receptors ranged from 600 to 29,000 per cell. In the majority of patients, both high- and low-affinity binding sites were identified. Neither the number of receptors per cell nor the finding of one or two classes of receptors correlated with growth response to SCF. Autoradiographic analysis of 125I-SCF binding to normal marrow mononuclear cells revealed grains associated with blasts and megakaryocytes. Grain counts on blasts from 10 AML patients and on normal marrow blasts suggested that high-affinity c-kit receptor expression on AML blasts is lower than or similar to that of normal blasts. These results identify c-kit receptors on human AML blasts, and indicate that SCF acts synergistically with IL-3 or GM-CSF to stimulate colony growth from the marrow cells of a portion of patients with AML.

A novel recombinant dual human SCF expressed in and purified from silkworm, Bombyx mori, possesses higher bioactivity than recombinant monomeric human SCF

“…The K d value of rdhSCF (29.4 pm,) was higher than that of rhSCF (45.2 pm). This result agreed with other published results about the binding affinity of SCF to its receptor (8,27,28), indicating that higher binding affinity to receptor should be responsible for After incubation, the activity was assayed as described under ÔMaterials and methodsÕ. The ED50 of rdhSCF, E. coliderived rhSCF and insect-derived rhSCF were 0.33, 2.87 and 3.03 ng/mL, respectively.…”

Growth factor receptor profile of CD34+ cells in AML and B‐lineage ALL and in their normal bone marrow counterparts

“…The broad range of expression of these receptors could, however, correlate with the heterogeneous response of the cells to growth factors described in other reports. IL-3 (38,39), SCF (31,41), IL-6 (35, 42) and G-CSF (36,43) stimulated the proliferation of the leukaemic cells in only some of the AML patients. IL-3 (40,44,45) and IL-7 (46±48) induced a proliferative response in part of the B-lineage ALL samples.…”

“…In this study, AML and B-lineage ALL CD34 + cells expressed the same growth factor receptors as their normal counterparts, but often at different levels. In other reports, the receptor expression on the leukaemic cells seemed not to be different from normal, but mononuclear cell suspensions were examined and these contained different cell types and maturation stages (30,31). When a cut-off for positivity was set at 20% of positive cells, all AML samples could be identi®ed Reactivity expressed as percentage of CD34 + bone marrow cells and as percentage of acute leukaemia samples.…”

High frequency of concomitant mastocytosis in patients with acute myeloid leukemia exhibiting the transforming KIT mutation D816V

“…The ligand of KIT, stem cell factor (SCF), promotes growth and colony-formation of myeloid progenitor cells as well as the differentiation of MC (Zsebo et al, 1990;Tsai et al, 1991;Valent et al, 1992;Kirshenbaum et al, 1992). It has also been described that in a group of patients with AML, blast cells express KIT and grow in response to the KIT-ligand SCF (Bü hring et al, 1991;Broudy et al, 1992). A number of previous and more recent studies have shown that certain somatic mutations in KIT can lead to autophosphorylation of the receptor and consecutive autonomous growth of affected cells (Furitsu et al, 1993;Ashman et al, 2000;Feger et al, 2002).…”