Mechanism of action of Histone Deacetylase inhibitor. Givinostat in Chronic Myeloproliferative neplasm

We investigated the mechanism of action of the histone deacetylase inhibitor Givinostat (GVS) in Janus kinase 2 (JAK2)V617F myeloproliferative neoplasm (MPN) cells. GVS inhibited colony formation and proliferation and induced apoptosis at doses two- to threefold lower in a panel of JAK2V617F MPN compared to JAK2 wild- type myeloid leukemia cell lines. By global gene expression analysis, we observed that GVS modulated 293 common genes in the JAK2V617F cell lines HEL and UKE1. In particular, the hematopoietic transcription factors NF-E2 and C-MYB were downmodulated by the drug specifically in JAK2V617F cells at both the RNA and protein level. GVS had a direct effect on the NF-E2 promoters, as demonstrated by specific enrichment of associated histone H3 acetylated at lysine 9. Modulation by GVS of NF-E2 was also observed in freshly isolated CD34+ cells from MPN patients, and was accompanied by inhibition of their proliferation and differentiation toward the erythroid lineage. We conclude that GVS acts on MPN cells through dual JAK2-STAT 5-extracellular signal- regulated kinase 1/2 inhibition and downmodulation of NF-E2 and C-MYB transcription. In the second part of the thesis we investigated whether clinically achievable concentrations of the histone deacetylase (HDAC) inhibitors givinostat and hydroxyurea induce synergistic cytotoxicity in Jak2V617F cells in vitro and through which possible mechanism. The results suggest that combined treatment with givinostat and hydroxyurea is a potential strategy for the management of Jak2V617F myeloproliferative neoplasms.