Received for publication April 5, 2007.
Revised July 25, 2007.
Accepted for publication July 25, 2007.

Identification of two New Synthetic Histone Deacetylase Inhibitors that Modulate Globin Gene Expression in Erythroid Cells from Normal Donors and Thalassemic Patients

Abstract

We have identified two new histone deacetylase (HDAC) inhibitors (9 and 24) capable to induce the expression of g-globin and/or -globin promoter-driven reporter genes in a synthetic model of Hb switch. Both compounds also increased, with different mechanisms, the /(+) ratio expressed in vitro by normal human erythroblasts. Compound 9, increased the levels of -globin mRNA, and the /(+) ratio (both by 2-fold). Compound 24, increased by 3-fold the level of -globin and decreased by 2-fold that of -globin mRNA, increasing the /(+) ratio by 6-fold, and raising (by 50%) the cell HbF content. Both compounds raised the acetylation state of histone H4 in primary cells, an indication that their activity was mediated through HDAC inhibition. Compound 9 and 24 were also tested as /(+) mRNA inducers in erythroblasts obtained from ⁰-thalassemic patients. Progenitor cells from ⁰-thalassemic patients generated in vitro morphologically normal pro-erythroblasts that, unlike normal cells, failed to mature in the presence of EPO and expressed low -globin levels, but levels of the alpha hemoglobin stabilizing protein (AHSP) mRNA 10-times higher than normal. Both compounds ameliorated the impaired in vitro maturation in ⁰-thalassemic erythroblasts decreasing AHSP expression down to normal levels. In the case of two patients (out of 5 analyzed), the improved erythroblast maturation was associated with detectable increases in the /(+) mRNA ratio. The low toxicity exerted by compounds 9 and 24 in all of the assays investigated suggests that these new HDAC inhibitors should be considered for personalized therapy of selected ⁰-thalassemic patients.

Key words: Regulation of gene expression, Regulation - post-transcriptional, Regulation - transcriptional, Transcription targets