Effect of Recombinant Human D‐Factor on the Growth of Leukemic Blast Progenitors from Acute Myeloblastic Leukemia Patients

We studied the effects of D‐factor on the growth of leukemic blast progenitors from 15 patients with acute myeloblastic leukemia and two leukemia cell lines in methylcellulose and suspension cultures. When stimulated by granulocyte colony‐stimulating factor (G‐CSF), granulocyte‐macrophage colony‐stimulating factor or interleukin‐3, leukemic blast progenitors undergo terminal division with limited differentiation in methylcellulose culture, forming blast colonies. Leukemic blast progenitors can renew themselves. The self‐renewal can be detected as secondary colony formation after replating primary blast colonies in fresh methylcellulose media and by the growth of clonogenic cells in suspension culture. D‐Factor suppressed primary and secondary colony formation in methylcellulose culture. Furthermore, D‐factor suppressed clonogenic cell recovery in suspension culture. The suppression by D‐factor of the growth of leukemic blast progenitors was not significantly dependent upon the colony‐stimulating factors used as growth‐stimulating factors. High concentration of G‐CSF did not overcome the suppressive effect of D‐factor. The results indicate that D‐factor is effective in suppressing not only terminal division but also self‐renewal of leukemic blast progenitors.