J Biol Chem, Vol. 273, Issue 27, 16921-16926, July 3, 1998

Induction of the Erythropoietin Receptor Gene and Acquisition of Responsiveness to Erythropoietin by Stem Cell Factor in HML/SE, a Human Leukemic Cell Line

Takeshi Sato, Sumiko Watanabe^§, Eizaburo Ishii^¶, Kohichiro Tsuji, and Tatsutoshi Nakahata

From the Departments of  Clinical Oncology and ^§ Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan and the ^¶ Department of Hematology and Oncology, Nagano Children's Hospital, 3100 Toyoshina, Toyoshina-cho, Minamiazumi-gun, Nagano 399-82, Japan

HML/SE is a cytokine-dependent cell line established from childhood acute megakaryoblastic leukemia. Granulocyte-macrophage colony-stimulating factor or stem cell factor (SCF) alone could stimulate proliferation of HML/SE cells, however interleukin-3, interleukin-6, granulocyte colony-stimulating factor and thrombopoietin could not. Although erythropoietin (EPO) alone stimulated neither proliferation nor differentiation of HML/SE cells, it did stimulate proliferation of HML/SE cells and production of hemoglobin in the presence of SCF. SCF activated the human EPO receptor promoter and induced EPO receptor gene expression. Given these results, we speculate that HML/SE cells acquired responsiveness to EPO via the EPO receptor induced by SCF. Mutation analysis of putative transcription factor binding sites in the human EPO receptor promoter suggested that Sp1, rather than the GATA-1 binding site, contributed to the induction of the hEPOR gene. Although it is well documented that hematopoietic stem cells and primitive progenitors require both an early-acting cytokine and a lineage-specific cytokine to differentiate to a certain lineage, related mechanisms are not well understood. HML/SE may serve as an excellent model system to analyze functions of early-acting cytokine SCF and lineage-specific cytokine EPO related to proliferation and differentiation of hematopoietic stem cells.