Effect of recombinant human M-CSF on the proliferation of leukemic blast progenitors in AML patients

We studied the effects of recombinant human macrophage colony-stimulating factor (M-CSF) on the leukemic blast progenitors from 10 acute myeloblastic leukemia patients. Recombinant human (rh)M-CSF stimulated leukemic blast progenitors in methylcellulose in four patients, but the colonies by rhM-CSF were smaller in size and number than those by rh-granulocyte-CSF or human bladder carcinoma cell line 5637 conditioned medium. rhM-CSF did not increase the number of clonogenic cells in long-term suspension culture. The blast colony formation in methylcellulose and the exponential growth of clonogenic cells in long-term suspension culture are considered to reflect the terminal divisions and the self-renewal of blast progenitors, respectively. The results show that M-CSF stimulates terminal divisions weakly but does not stimulate self-renewal of leukemic blast progenitors. M-CSF did not induce differentiation of blasts either in methylcellulose or in suspension culture.