Hydroxyurea reduces the levels of the fetal gene repressors ZBTB7A/LRF and BCL11A in erythroid cells .

OBJECTIVES

Hydroxyurea (HU) is the most widely used therapy for adults and children with sickle cell disease (SCD). It is believed to act largely by inducing the transcription of fetal genes to generate fetal hemoglobin (HbF), which inhibits the pathological polymerization of sickle hemoglobin (HbS). The mechanisms by which hydroxyurea elevates HbF are unclear. We explored the hypothesis that hydroxyurea induces HbF expression by inhibiting the expression of 2 gene repressors, BCL11A and ZBTB7A (also known as LRF), which normally bind the gene promoters to inhibit their expression after birth.

METHODS

We treated immortalized murine erythroleukemia cells and normal human donor CD34 hematopoietic stem and progenitor cell-derived erythroblasts with hydroxyurea and measured the effects on globin, BCL11A and ZBTB7A protein and mRNA expression.

RESULTS

Treating murine erythroleukemia cells or human CD34 hematopoietic stem and progenitor cell-derived erythroblasts with hydroxyurea reduced the protein levels of BCL11A and ZBTB7A compared to the vehicle-treated control. mRNA levels were reduced in both cell types upon hydroxyurea treatment. However, mRNA levels were only reduced in human CD34 hematopoietic stem and progenitor cell-derived erythroblasts.

CONCLUSIONS

Hydroxyurea can act in erythroid cells to reduce the levels and activity of two direct fetal transcriptional repressors with accompanying de-repression of the genes and induction of HbF, which may explain the mechanism of action leading to amelioration of symptoms in SCD patients treated with this drug.