Stromal Cell‐dependent Growth of Leukemic Cells from Murine Erythroblastic Leukemia

Transplantable erythroblastic leukemia was induced by 300‐rad irradiation of C3H mice. Conditions for in vitro growth of the leukemic cells were studied. None of interleukin‐3, granulocyte/macrophage colony‐stimulating factor and erythropoietin could support the growth of the cells in vitro. In contrast, the leukemic cells grew into a stroma‐dependent cell line, ELM‐D, in close contact with the stromal cell layer of 900‐rad‐irradiated long‐term bone marrow culture. A stroma‐independent cell line, termed ELM‐I‐1, was further established from the non‐adherent population in the co‐culture of the leukemic cells, ELM‐D, with stromal cells. Reverse transcriptase activity was not detectable in ELM‐D or ELM‐I‐1 cells. Studies on binding and cross‐linking of (125)I‐erythropoietin showed that ELM‐I‐1 cells had erythropoietin receptors, and two major radiolabeled protein products with molecular weights of 120 kDa and 140 kDa were detected on sodium dodecyl sulfate/polyacrylamide gel electrophoresis under reducing conditions.