PERK/NRF2 and autophagy form a resistance mechanism against G9a inhibition in leukemia stem cells
Open Access
- 15 April 2020
- journal article
- research article
- Published by Springer Science and Business Media LLC in Journal of Experimental & Clinical Cancer Research
- Vol. 39 (1), 1-14
- https://doi.org/10.1186/s13046-020-01565-3
Abstract
The histone methyltransferase G9a has recently been identified as a potential target for epigenetic therapy of acute myeloid leukemia (AML). However, the effect of G9a inhibition on leukemia stem cells (LSCs), which are responsible for AML drug resistance and recurrence, is unclear. In this study, we investigated the underlying mechanisms of the LSC resistance to G9a inhibition. We evaluated the effects of G9a inhibition on the unfolded protein response and autophagy in AML and LSC-like cell lines and in primary CD34+CD38− leukemic blasts from patients with AML and investigated the underlying mechanisms. The effects of treatment on cells were evaluated by flow cytometry, western blotting, confocal microscopy, reactive oxygen species (ROS) production assay. The G9a inhibitor BIX-01294 effectively induced apoptosis in AML cell lines; however, the effect was limited in KG1 LSC-like cells. BIX-01294 treatment or siRNA-mediated G9a knockdown led to the activation of the PERK/NRF2 pathway and HO-1 upregulation in KG1 cells. Phosphorylation of p38 and intracellular generation of reactive oxygen species (ROS) were suppressed. Pharmacological or siRNA-mediated inhibition of the PERK/NRF2 pathway synergistically enhanced BIX-01294-induced apoptosis, with suppressed HO-1 expression, increased p38 phosphorylation, and elevated ROS generation, indicating that activated PERK/NRF2 signaling suppressed ROS-induced apoptosis in KG1 cells. By contrast, cotreatment of normal hematopoietic stem cells with BIX-01294 and a PERK inhibitor had no significant proapoptotic effect. Additionally, G9a inhibition induced autophagy flux in KG1 cells, while autophagy inhibitors significantly increased the BIX-01294-induced apoptosis. This prosurvival autophagy was not abrogated by PERK/NRF2 inhibition. PERK/NRF2 signaling plays a key role in protecting LSCs against ROS-induced apoptosis, thus conferring resistance to G9a inhibitors. Treatment with PERK/NRF2 or autophagy inhibitors could overcome resistance to G9a inhibition and eliminate LSCs, suggesting the potential clinical utility of these unique targeted therapies against AML.Keywords
Funding Information
- National Research Foundation of Korea (NRF-2018R1C1B5047502)
- Yuhan Corporation
This publication has 53 references indexed in Scilit:
- Autophagy and chemotherapy resistance: a promising therapeutic target for cancer treatmentCell Death & Disease, 2013
- The high Nrf2 expression in human acute myeloid leukemia is driven by NF-κB and underlies its chemo-resistanceBlood, 2012
- The PERK-eIF2α phosphorylation arm is a pro-survival pathway of BCR-ABL signaling and confers resistance to imatinib treatment in chronic myeloid leukemia cellsCell Cycle, 2012
- Redox signaling loops in the unfolded protein responseCellular Signalling, 2012
- Discovery of 7-Methyl-5-(1-{[3-(trifluoromethyl)phenyl]acetyl}-2,3-dihydro-1H-indol-5-yl)-7H-pyrrolo[2,3-d]pyrimidin-4-amine (GSK2606414), a Potent and Selective First-in-Class Inhibitor of Protein Kinase R (PKR)-like Endoplasmic Reticulum Kinase (PERK)Journal of Medicinal Chemistry, 2012
- Resistance of leukemic stem-like cells in AML cell line KG1a to natural killer cell-mediated cytotoxicityCancer Letters, 2012
- Epigenetic regulation of miRNA genes in acute leukemiaLeukemia, 2011
- Epigenetic modifications as therapeutic targetsNature Biotechnology, 2010
- Signal integration in the endoplasmic reticulum unfolded protein responseNature Reviews Molecular Cell Biology, 2007
- Induction of Apoptosis by ASK1, a Mammalian MAPKKK That Activates SAPK/JNK and p38 Signaling PathwaysScience, 1997