Identification and Analysis of Human Erythropoietin Receptors on a Factor - Dependent Cell Line , TF -

We have recently established a novel cell line, TF-1 , from bone marrow cells of a patient with erythroleukemia. that showed an absolute growth dependency on each of three hematopoietic growth factors: erythropoietin (EPO) granulocyte-macrophage colony-stimulating factor (GM-CSF), and interleukin 3 (11-3). EPO stimulated the proliferation of TF-1 cells even at the physiologic concentration (0.03 U/mi). We performed binding experiments on TF-1 cells using radioiodinated EPO. The binding of radioiodinated EPO to TF-1 was specific, timeand temperature-dependent, and saturable. Scatchard analysis of the saturation binding data suggested the existence of a single class of binding sites (kd = 0.40 nmol/L; number of binding