Effects of stem cell factor (SCF) on the in vitro growth of leukemic blast progenitors in acute non-lymphocytic leukemia.

We studied the effects of recombinant human stem cell factor (SCF) on the growth of leukemic blast progenitors obtained from 27 acute non-lymphocytic leukemia (ANLL) patients and 1 chronic myelocytic leukemia patient in myeloid crisis; the effects varied among the patients. While SCF did not have stimulatory effects in the cells of 7 patients, it stimulated primary and secondary blast colony formation in methylcellulose culture and the recovery of clonogenic cells in suspension cultures from 21 patients. SCF stimulated leukemic blast progenitors in a manner almost comparable to or more prominently than that of other CSFs, namely, IL-3, GM-CSF, and G-CSF, in 9 patients. One patient responded to SCF but not to the other CSFs. In another 11 patients, SCF was less effective on leukemic blast progenitors than the other CSFs tested. To explain the variable effects of SCF, we investigated the relation between the phenotype of leukemic blasts and responsiveness to this agent; the response was significantly higher in patients with CD34-positive blasts than in those with CD34-negative blasts. These results imply that responsiveness to SCF differs among leukemic blast progenitors originating at different hematopoietic stages. In some ANLL patients, SCF showed synergy with other CSFs, suggesting that SCF may be involved in the cytokine network affecting leukemic hematopoiesis.