The histone methyltransferase inhibitor, DZNep, up-regulates TXNIP, increases ROS production, and targets leukemia cells in AML

Abstract Recent studies have shown that 3-Deazaneplanocin A (DZNep), a histone methyltransferase inhibitor, disrupts polycomb-repressive complex 2 (PRC2), and preferentially induces apoptosis in cancer cells, including acute myeloid leukemia (AML). However, the underlying molecular mechanisms are not well understood. The present study demonstrates that DZNep induces robust apoptosis in AML cell lines, primary cells, and targets CD34+CD38− leukemia stem cell (LSC)–enriched subpopulations. Using RNA interference (RNAi), gene expression profiling, and ChIP, we identified that TXNIP, a major redox control molecule, plays a crucial role in DZNep-induced apoptosis. We show that disruption of PRC2, either by DZNep treatment or EZH2 knockdown, reactivates TXNIP, inhibits thioredoxin activity, and increases reactive oxygen species (ROS), leading to apoptosis. Furthermore, we show that TXNIP is down-regulated in AML and is a direct target of PRC2-mediated gene silencing. Consistent with the ROS accumulation on DZNep treatment, we also see a signature of endoplasmic reticulum (ER) stress-regulated genes, commonly associated with cell survival, down-regulated by DZNep. Taken together, we uncover a novel molecular mechanism of DZNep-mediated apoptosis and propose that EZH2 may be a potential new target for epigenetic treatment in AML.

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Oxidative Stress and ROS-Mediated Signaling in Leukemia: Novel Promising Perspectives to Eradicate Chemoresistant Cells in Myeloid Leukemia

International Journal of Molecular Sciences ◽

10.3390/ijms22052470 ◽

2021 ◽

Vol 22 (5) ◽

pp. 2470

Author(s):

Silvia Trombetti ◽

Elena Cesaro ◽

Rosa Catapano ◽

Raffaele Sessa ◽

Alessandra Lo Bianco ◽

...

Keyword(s):

Oxidative Stress ◽

Myeloid Leukemia ◽

Molecular Mechanisms ◽

Hematological Malignancies ◽

Leukemic Cells ◽

Leukemia Cells ◽

Ros Production ◽

Oxygen Species ◽

Cellular Redox ◽

Ros Homeostasis

Myeloid leukemic cells are intrinsically under oxidative stress due to impaired reactive oxygen species (ROS) homeostasis, a common signature of several hematological malignancies. The present review focuses on the molecular mechanisms of aberrant ROS production in myeloid leukemia cells as well as on the redox-dependent signaling pathways involved in the leukemogenic process. Finally, the relevance of new chemotherapy options that specifically exert their pharmacological activity by altering the cellular redox imbalance will be discussed as an effective strategy to eradicate chemoresistant cells.

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DJ-1 Plays an Important Role in Homoharringtonine-Induced Apoptosis of Imatinib-Resistant Chronic Myeloid Leukemia Cells

Blood ◽

10.1182/blood.v124.21.5956.5956 ◽

2014 ◽

Vol 124 (21) ◽

pp. 5956-5956

Author(s):

Xuan Zhou ◽

Na Xu ◽

Rong Li ◽

Lin Li ◽

Li Ding ◽

...

Keyword(s):

Chronic Myeloid Leukemia ◽

Myeloid Leukemia ◽

Molecular Mechanisms ◽

Annexin V ◽

K562 Cells ◽

Molecular Therapy ◽

Leukemia Cells ◽

Control Group ◽

Imatinib Resistant ◽

Induced Apoptosis

Abstract Background and Objective: Although the treatment of chronic myeloid leukemia (CML) has improved since the introduction of tyrosine kinase inhibitors (TKI), cases of resistance have been reported and resulted in challenges to the treatment. Recent studies have suggested that Homoharringtonine (HHT), a cephalotaxine ester, has demonstrated a clinical activity in imatinib-resistant CML patients, however, the molecular mechanisms underlying this phenomenon are unknown. Our previous study found that treatment with HHT significantly increased apoptosis of K562 cells. Moreover, the protein DJ-1, identified by two-dimensional polyacrylamide gel electrophoresis and mass spectrometry, was demonstrated to decrease after HHT treatment. Therefore, we performed the experiment to address the hypothesis that DJ-1 might play an important role in Homoharringtonine-induced apoptosis of Imatinib-resistant chronic myeloid leukemia cells Methods and Results: To find the pivotal protein by HHT, Imatinib-resistant K562 cells were treated with HHT (10 ug/ml) for 5 h, 12 h, 24 h respectively and the control group without HHT were harvested to assess apoptosis with Annexin V-FITC and propidium iodide per the manufacturer’s protocol and analyzed by ﬂow cytometry. The data indicated a time dependent induction of apoptosis by HHT, with the number of apoptotic cells (FITC-Annexin-V and PI double-positive cells) signiﬁcantly increasing from 2.2± 1.5 % in control to 35.9 ± 6.7% in cells treated with HHT for 24 h (P<0.01). The protein DJ-1 expression change upon HHT treatment which were analyzed with western blot, found that the protein level of DJ-1 had significantly decreased after the treatment of HHT for 24 h. Furthermore, primary cells from six CML patients and three healthy donors were obtained with informed consent and divided into three groups: the CML-CP group (three newly diagnosed patients in the chronic phase), the imatinib-resistant CML group(three imatinib-resistant patients in the blastic phase) and the control group. Mononuclear cells were all cultured in vitro in the absence and presence of 10 mg/ml HHT for 5 h and 24 h. The results showed that DJ-1 expression in primary leukemia cells (both CML-CP group and imatinib-resistant CML group) were found to be decreased after HHT treatment and the expression level of DJ-1 seemed lower in the healthy donor as compared to primary CML cells, moreover, the protein changes induced by HHT were significantly different among three groups and the protein changes were not as significant in CML-CP cells as in imatinib-resistant CML cells (P<0.05). Conclusions: These findings indicated that DJ-1 might play an important role in Homoharringtonine-induced apoptosis of Imatinib-resistant chronic myeloid leukemia cells. Further study may help to assess a promising potential of this protein to be used as a target for a molecular therapy. Disclosures No relevant conflicts of interest to declare.

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