Inhibition by retinoic acid of myeloid progenitors in chronic myeloid leukemia and myeloproliferative disease: increased sensitivity in blastic phase of chronic myeloid leukemia

Abstract

The effects of all-trans retinoic acid (RA) were tested on the growth in vitro of myeloid progenitors from peripheral blood or bone marrow, in 25 patients with chronic myeloid leukemia (CML), ten of whom were either in accelerated or blastic phase, and in nine patients with myeloproliferative disease (MPD). The responses were compared with 12 normal bone marrow controls obtained from patients with lymphoma. Clonal growth in CML blastic and accelerated phase was inhibited to the greatest degree (mean 49 +/- 9% (SEM) of control at 0.3 microM RA). The responses in CML chronic phase and MPD were more heterogeneous, but significant inhibition was seen at higher concentrations of RA (50 +/- 12% CML chronic phase, 58 +/- 26% MPD at 3.0 microM RA). At 0.3 microM and 1.0 microM RA there were significant differences between the CML chronic phase and the CML blastic phase patients (p less than 0.02 and p less than 0.05 respectively). At these concentrations there was no significant inhibition on normal bone marrow myeloid progenitors. Inhibition was independent of the proportions of progenitors in S phase, as assessed by tritiated thymidine suicide. Preincubation of cells from selected patients with RA for 48 hours before culture in agar resulted in a significant degree of inhibition (48 +/- 8% of control). Inhibition was prevented by delaying the addition of RA from 24 to 48 hours from the beginning of the culture, indicating that RA exerts an early direct effect on myeloid progenitors.