The Histone Methyltransferase Inhibitor, DZNep, Upregulates TXNIP, Increases ROS Production and Targets Leukemia Cells In AML

Targeting epigenetic abnormalities is an emerging therapeutic strategy in AML. Unlike inhibition of DNA methylation and histone deacetylase, inhibition of histone methylation, has been under-explored in AML.

A novel histone methytransferase inhibitor, DZNep, was used to treat a panel of AML cell lines (in vitro and in mouse models), primary patient cells and leukemia stem cells (LSCs). Flow cytometry was used to determine apoptosis and reactive oxygen species (ROS) production. RNA interference (RNAi), gene expression profiling (GEP), and chromatin immunoprecipitation (ChIP) were used to study the molecular mechanism of DZNep.

DZNep depleted EZH2, a histone methyltransferase, and induced robust apoptosis in AML cell lines, both in vitro and in mouse model, in primary AML cells, and targeted LSCs while sparing normal haematopoietic stem cells. On GEP, polymerase chain reaction (PCR) and western blot, TXNIP, a major redox control molecule, was one of the most upregulated molecules upon DZNep treatment. Either DZNep treatment or EZH2 knockdown reactivated TXNIP and increased ROS, leading to apoptosis. TXNIP over-expression also produced the same phenotype. Furthermore, TXNIP was downregulated in AML and a direct target of EZH2-mediated gene silencing. We also saw a signature of downregulation of endoplasmic reticulum (ER)-stress regulated pro-survival genes, suggesting a novel function of EZH2 in regulation of stress response.

DZNep and EZH2 inhibition has therapeutic potential in AML, in which treatment has not change in 20 years. We delineated that the effect of DZNep is specifically mediated through EZH2 and TXNIP, and highlighted the importance of histone methylation, redox regulation and ER stress in AML biology.

No relevant conflicts of interest to declare.