OMA-AML-1: A leukemic myeloid cell line with CD34⁺ progenitor and CD15⁺ spontaneously differentiating cell compartments

OMA-AML-1 was established from a patient with acute myelomonocytic (M4) leukemia at fifth relapse when blasts were greater than 85% CD34⁺, CD15^-. Leukemic cells were established in suspension culture and independently grown as subcutaneous tumors in SCID mice. Cells growing in suspension culture underwent differentiation by phenotypic and morphologic criteria. In contrast, cells grown as subcutaneous solid tumors in SCID mice maintained progenitor cell characteristics with high-density CD34 expression and lack of morphologic differentiation. A tendency toward differentiation to CD15⁺, CD34^- cells in vitro and self-renewal of CD34⁺, CD15^- cells in vivo was consistently demonstrated regardless of whether cells were initially grown in vitro or in vivo. The cell line maintains both a CD34⁺, CD15^- progenitor cell pool and a non-overlapping, CD15⁺, CD34^- differentiating cell compartment after more than 1 year in continuous culture. Cell cycle analysis and cloning experiments were consistent with terminal differentiation occurring in the CD15⁺, CD34^- population. The cell line shows concentration-dependent proliferative responses to interleukin (IL)-3, granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL-6, but not to granulocyte CSF (G-CSF). OMA-AML-1 appears to mimic several features of normal myeloid hematopoiesis and should prove useful for the study of normal and malignant myeloid differentiation.