Role of humoral and cellular factors on the growth of blast progenitors of acute myeloblastic leukemia in serum-free culture

To determine the growth requirement of leukemic blast progenitors in acute myeloblastic leukemia (AML), leukemic cells from the peripheral blood of eight AML patients were cultured in the serum-free culture system. Blast progenitors made colonies in methylcellulose culture and showed exponential growth in suspension culture, although the growth of blast progenitors in the absence of fetal calf serum (FCS) in some patients was inferior to that in the FCS-enhanced culture system. Recombinant human granulocyte colony-stimulating factor (rhG-CSF) stimulated the growth of blast progenitors in a dose-responsive manner. When cells were cultured at high cell density, blast colonies were formed even in the absence of CSF. Irradiated blasts also supported the growth of intact blast progenitors. These results confirm the finding noted in the FCS-enhanced culture studies that granulopoietic factor, G-CSF, plays an important role on the leukemic growth. The importance of cell to cell interaction for the growth of blast progenitors was also confirmed.