Response of leukemic cells to the sequential combination of GM-CSF and G-CSF.

We designed two experiments using delayed stimulation by granulocyte/macrophage colony-stimulating factor (GM-CSF) or granulocyte colony-stimulating factor (G-CSF) with colony-type analysis in order to elucidate the characteristics of factor-dependent proliferation and differentiation of leukemic progenitor cells. Eight patients with acute myelogenous leukemia showing non-autonomous colony growth were selected. Three of the six cases showed that delayed addition of G-CSF to agar culture initiated by GM-CSF had no influence on the type and number of colonies; whereas, delayed addition of GM-CSF to G-CSF resulted in additional GM colonies. These findings were the same for normal bone marrow progenitors. In two cases, granulocytic colonies markedly increased with delayed addition of G-CSF to GM-CSF. Synergism occurred in one case where GM-CSF was used first. In the next experiment, regardless of whether CSF was used during the 48 hour preincubation, subsequent colony types were affected by the CSF used in agar culture. But colony numbers increased 1.5 fold in two of six cases by preincubation with GM-CSF, and 1.2 to 1.7 fold in all normal cases by preincubation with G-CSF. These results suggest that although there is a great heterogeneity in the response to CSF, some leukemic progenitors act like normal progenitors.