Azacitidine differentially affects CD4pos T-cell polarization in vitro and in vivo in high risk myelodysplastic syndromes

CD4pos T-cell subsets play a role in myelodysplastic syndromes (MDS) pathogenesis and may be affected upon 5-azacitidine (Aza) treatment. Aza enhanced human TH1 frequencies in vitro but not in vivo. The proportion of functional FoxP3pos regulatory T cells (Treg) was enhanced by Aza in vitro (p < 0.0002), and a modest, temporary increase was observed in vivo (p = 0.08). The overall number of TH17 was reduced both in vitro (p < 0.03) and in vivo (p < 0.006), indicating that Aza directly affects CD4pos polarization during activation in vitro. Upon in vivo treatment in high risk MDS patients, particularly the TH17-Treg axis is affected.