The effect of imatinib mesylate on the erythroid colony formation from patients with polycythemia vera in the presence of different cytokines.

It has been shown that imatinib mesylate, a drug used in the treatment of chronic myelogenous leukemia, inhibits the effect of stem cell factor, which has a central role in erythropoiesis. In some polycythemia vera (PV) patients, it has inhibited autonomous erythroid colony growth in vitro and decreased the need for phlebotomy. In this study we have investigated the effect of insulin like growth factor (IGF)-I, stem cell factor (SCF) and erythropoietin (Epo) with interleukin (IL)-3, granulocyte macrophage-colony stimulating factor (GM-CSF) and granulocyte-colony stimulating factor (G-CSF) in the presence of imatinib mesylate on the erythroid progenitors derived from peripheral blood mononuclear cells of three patients with PV and four healthy controls in semisolid medium. Erythroid colony formation from hematopoietic progenitors obtained from healthy controls was observed only in the presence of all cytokines. However, the number of erythroid colonies could not reach that of patients with PV. Inhibition of imatinib mesylate on erythroid colony growth was evident. Hematopoietic progenitors of patients with PV displayed two types of colony formation: the first type was exogenous cytokine-independent and was hypersensitive to current cytokines, and the second displayed hypersensitivity to current exogenous cytokines, but was exogenous cytokine-dependent. For both types, the inhibitory effect of imatinib mesylate was striking in the presence of all cytokines including IL-3, GM-CSF and Epo. There is no direct evidence yet that imatinib mesylate could inhibit the effect of IL-3, G-CSF, GM-CSF, Epo and IGF-I on erythropoiesis. Considering former studies together with results of this study, it can be argued that imatinib mesylate is effective in PV on the intersecting signal transduction mechanisms in which stem cell factor and its receptor may have a part.