We report in this paper that the
DNA-binding
drug mithramycin is a potent inducer of
gamma-globin mRNA accumulation and
fetal hemoglobin (HbF) production in erythroid cells from healthy human subjects and
beta-thalassemia patients. Erythroid precursors derived from peripheral blood were grown in 2-phase liquid culture. In this procedure, early erythroid progenitors proliferate and differentiate during phase 1 (in the absence of
erythropoietin) into late progenitors. In phase 2, in the presence of
erythropoietin, the latter cells continue their proliferation and mature into Hb-containing orthochromatic normoblasts. Compounds were added on days 4 to 5 of phase 2 (when cells started to synthesize Hb), and cells were harvested on day 12. Accumulation of mRNAs for
gamma-globin,
beta-globin,
alpha-globin,
glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and
beta-actin were measured by real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR); induction of HbF was analyzed by high-performance liquid chromatography (HPLC) and, at cellular level, by flow cytometry. We demonstrated that
mithramycin was able to up-regulate preferentially
gamma-globin mRNA production and to increase HbF accumulation, the percentage of HbF-containing cells, and their HbF content.
Mithramycin was more effective than
hydroxyurea, being, in addition, not cytotoxic. This was shown by the lack of cytotoxicity on erythroid and myeloid in vitro primary cell cultures treated with
mithramycin at concentrations effective for HbF induction. These results are of potential clinical significance because an increase of HbF alleviates the symptoms underlying
beta-thalassemia and
sickle cell anemia. The results of this report suggest that
mithramycin and its analogs warrant further evaluation as potential therapeutic drugs.