CSF2 and acute myeloid leukemia: Cytokine-dependent—granulocyte macrophage colony stimulating factor (GM-CSF), stem cell factor (SCF), and Flt3 ligand (Flt3L)—AML cell proliferation in suspension cultures was investigated for all 79 patients, and proliferation was assayed as (3H)-thymidine incorporation after seven days of in vitro culture, when the proliferative response reflects an enrichment of clonogenic cells [42].