Granulocyte-Macrophage Colony-Stimulating Factor-Dependent Growth and Erythropoietin-Induced Differentiation of a Human Cell Line MB-02

Abstract

AbstractPeripheral blood blasts from a patient with acute megakaryoblastic leukemia were placed into liquid cultures with recombinant growth factors. Growth, but not differentiation, was supported by interleukin-3 (IL-3) or granulocyte-macrophage colony-stimulating factor (GM-CSF) for the first 30 days of culture. Sustained growth occurred only with GM-CSF and gave rise to the cell line MB-02, which has been in continuous culture for over 1 year. The cell line retained the surface phenotype of the leukemic megakaryoblasts except for the loss of glycoproteins lb and IIb/IIIa, which were induced after exposure to phorbol esters. The induction of erythropoiesis occurred when GM-CSF–deprived cells were cultured with erythropoietin (Epo). Well-defined morphologic stages of differentiation ranging from primitive erythroblasts to nucleiextruding normoblasts were seen. Transforming growth factor-β inhibited GM-CSF- and Epo-dependent growth, but not erythroid maturation. Indirect immunofluorescence using globin chain-specific monoclonal antibodies detected fetal, but not adult hemoglobin in the uninduced cells, β-globin was induced and γ-globin was increased after Epo exposure. Both globin species accumulated in the developing erythrocytes until terminal differentiation. Quantitative S1 analysis of β-like globin transcripts showed very low levels of ϵ- and β-globin expression and high levels of γ-globin expression in cells maintained in GM-CSF. Five days after induction with Epo, e message decreased to barely detectable levels while γ and β transcripts increased threefold and 20-fold, respectively. This novel cell line not only retains many characteristics of the leukemic megakaryoblasts from which it was derived, but also can be induced to recapitulate apparent normal erythropoiesis.