Pharmacological Induction of Human Fetal Globin Gene in Hydroxyurea-Resistant Primary Adult Erythroid Cells

Abstract

Pharmacological induction of the fetal γ globin gene and the consequent formation of HbF (α₂/γ₂) in adult erythroid cells are one feasible therapeutic strategy for sickle cell disease (SCD) and severe β-thalassemias. Hydroxyurea (HU) is the current drug of choice for SCD, but serious side effects limit its clinical use. Moreover, 30 to 50% of patients are irresponsive to HU treatment. We have used high-throughput screening to identify benzo[de]benzo[4,5]imidazo[2,1-a]isoquinolin-7-one and its derivatives (compounds I to VI) as potent γ globin inducers. Of the compounds, I to V exert superior γ globin induction and have better therapeutic potential than HU, likely because of their activation of the p38 mitogen-activated protein kinase (MAPK) signaling pathway and modulation of expression levels and/or chromosome binding of γ globin gene regulators, including BCL11A, and chromatin structure over the γ globin promoter. Unlike sodium butyrate (NaB), the global levels of acetylated histones H3 and H4 are not changed by compound II treatment. Remarkably, compound II induces the γ globin gene in HU-resistant primary human adult erythroid cells, the p38 signaling pathway of which appears to be irresponsive to HU and NaB as well as compound II. This study provides a new framework for the development of new and superior compounds for treating SCD and severe β-thalassemias.

ACKNOWLEDGMENTS

We thank Szu-Huei Wu of the Institute of Biotechnology and Pharmaceutical Research, NHRI, for preparation of the heterocyclic compound library used in our screening. We appreciate the technical assistance in HPLC analysis by Liang-in Lin and Su-Cheng Tseng in the National Taiwan University. The pLAR-β plasmid was a generous gift from M. Groudine (Fred Hutchinson Cancer Research Center). We also thank Miranda Loney for correcting grammatical errors and improving the quality of the manuscript.

This research was supported by a National Health Research Institute grant (NHRI-EX100-10011SI) and the Academia Sinica (AS), Taipei, Taiwan. C.-K.J.S. is an AS Senior Investigator Awardee.

Y.-C.C., R.-L.C., and Z.-S.L. designed and performed the experiments and analyzed the data; J.-S.S. and Y.-S.C provided critical compounds and helpful discussions during the course of this work; Y.-C.C. and C.-K.J.S. developed the project and wrote the manuscript.

We declare no conflict of interest.