5-Azacitidine in aggressive myelodysplastic syndromes regulates chromatin structure at PU.1 gene and cell differentiation capacity

Abstract

Epigenetic 5-azacitidine (AZA) therapy of high-risk myelodysplastic syndromes (MDS) and acute myelogenous leukemia (AML) represents a promising, albeit not fully understood, approach. Hematopoietic transcription factor PU.1 is dynamically regulated by upstream regulatory element (URE), whose deletion causes downregulation of PU.1 leading to AML in mouse. In this study a significant group of the high-risk MDS patients, as well as MDS cell lines, displayed downregulation of PU.1 expression within CD34 þ cells, which was associated with DNA methylation of the URE. AZA treatment in vitro significantly demethylated URE, leading to upregulation of PU.1 followed by derepression of its transcriptional targets and onset of myeloid differentiation. Addition of colony-stimulating factors (CSFs; granulocyte-CSF, granulocyte --macrophage-CSF and macrophage-CSF) modulated AZA-mediated effects on reprogramming of histone modifications at the URE and cell differentiation outcome. Our data collectively support the importance of modifying the URE chromatin structure as a regulatory mechanism of AZA-mediated activation of PU.1 and induction of the myeloid program in MDS.

Biomodulatory therapy induces complete molecular remission in chemorefractory acute myeloid leukemia

“…The most common APA-related adverse events were hematologic toxicities grade 1-4 (Table 1) Combined transcriptional targeting by PPARγ and RAR ligands as well as AZA treatment have been shown to induce myeloid differentiation and to attenuate leukemia cell growth. 4,[9][10][11] The induction of molecular CR, strong myeloid differentiation in leukemia blasts ( Figure 1C) and in residual hematopoiesis ( Figure 1B and data not shown) during APA treatment emphasizes our hypothesis that combined biomodulation with APA might act synergistically on leukemic differentiation and growth control. Previous data had already suggested that metronomic biomodulatory therapy approaches differentially target hallmarks of cancer, i.e.…”

Epigenetic therapy of cancer stem and progenitor cells by targeting DNA methylation machineries

“…For example, Aza-dC facilitates tumor necrosis factor alpha-induced monocytic differentiation of two AML cell lines NB4 and U937 by demethylation of DIF2 (also known as IER3) promoter and thus up-regulation of the gene [60] . Similarly, an upstream regulatory element within PU.1 promoter has been shown to be demethylated by Aza leading to an upregulation of PU.1 and its target genes [61] . Co-treatment of CD34 + cells derived from MDS patients by Aza and granulocyte colony-stimulating factor led to myeloid differentiation [61] .…”

“…Similarly, an upstream regulatory element within PU.1 promoter has been shown to be demethylated by Aza leading to an upregulation of PU.1 and its target genes [61] . Co-treatment of CD34 + cells derived from MDS patients by Aza and granulocyte colony-stimulating factor led to myeloid differentiation [61] . Another study has shown that AzadC induces expression of olfactomedin 4 (OLFM4), of which an over-expression led to apoptosis and differentiation HL60 cell line [62] .…”

Both mature KIR+ and immature KIR− NK cells control pediatric acute B-cell precursor leukemia in NOD.Cg-Prkdcscid IL2rgtmWjl/Sz mice

“…In line with the observation that 5-aza-cytidine may promote the differentiation of malignantly transformed cells by inducing the reexpression of epigenetically downregulated PU.1 36 and considering the crucial role that PU.1 plays in the regulation of NK-cell differentiation and homeostasis, 37 we assume that the re-expression of PU.1 might have promoted NK-cell differentiation in our model. In addition, it has been shown for low (but not high dose) 5-aza-cytidine therapy that this may increase the number of cells in the S phase, and may thus promote cell-cycle progression.…”