TY - JOUR
T1 - SIRT3 overexpression and epigenetic silencing of catalase regulate ROS accumulation in CLL cells activating AXL signaling axis
AU - Maiti, Guru P.
AU - Sinha, Sutapa
AU - Mahmud, Hasan
AU - Boysen, Justin
AU - Mendez, Mariana T.
AU - Vesely, Sara K.
AU - Holter-Chakrabarty, Jennifer
AU - Kay, Neil E.
AU - Ghosh, Asish K.
N1 - Publisher Copyright:
© 2021, The Author(s).
PY - 2021/5
Y1 - 2021/5
N2 - Mitochondrial metabolism is the key source for abundant ROS in chronic lymphocytic leukemia (CLL) cells. Here, we detected significantly lower superoxide anion (O2−) levels with increased accumulation of hydrogen peroxide (H2O2) in CLL cells vs. normal B-cells. Further analysis indicated that mitochondrial superoxide dismutase (SOD)2, which converts O2− into H2O2 remained deacetylated in CLL cells due to SIRT3 overexpression resulting its constitutive activation. In addition, catalase expression was also reduced in CLL cells suggesting impairment of H2O2-conversion into water and O2 which may cause H2O2-accumulation. Importantly, we identified two CpG-islands in the catalase promoter and discovered that while the distal CpG-island (−3619 to −3765) remained methylated in both normal B-cells and CLL cells, variable degrees of methylation were discernible in the proximal CpG-island (−174 to −332) only in CLL cells. Finally, treatment of CLL cells with a demethylating agent increased catalase mRNA levels. Functionally, ROS accumulation in CLL cells activated the AXL survival axis while upregulated SIRT3, suggesting that CLL cells rapidly remove highly reactive O2− to avoid its cytotoxic effect but maintain increased H2O2-level to promote cell survival. Therefore, abrogation of aberrantly activated cell survival pathways using antioxidants can be an effective intervention in CLL therapy in combination with conventional agents.
AB - Mitochondrial metabolism is the key source for abundant ROS in chronic lymphocytic leukemia (CLL) cells. Here, we detected significantly lower superoxide anion (O2−) levels with increased accumulation of hydrogen peroxide (H2O2) in CLL cells vs. normal B-cells. Further analysis indicated that mitochondrial superoxide dismutase (SOD)2, which converts O2− into H2O2 remained deacetylated in CLL cells due to SIRT3 overexpression resulting its constitutive activation. In addition, catalase expression was also reduced in CLL cells suggesting impairment of H2O2-conversion into water and O2 which may cause H2O2-accumulation. Importantly, we identified two CpG-islands in the catalase promoter and discovered that while the distal CpG-island (−3619 to −3765) remained methylated in both normal B-cells and CLL cells, variable degrees of methylation were discernible in the proximal CpG-island (−174 to −332) only in CLL cells. Finally, treatment of CLL cells with a demethylating agent increased catalase mRNA levels. Functionally, ROS accumulation in CLL cells activated the AXL survival axis while upregulated SIRT3, suggesting that CLL cells rapidly remove highly reactive O2− to avoid its cytotoxic effect but maintain increased H2O2-level to promote cell survival. Therefore, abrogation of aberrantly activated cell survival pathways using antioxidants can be an effective intervention in CLL therapy in combination with conventional agents.
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U2 - 10.1038/s41408-021-00484-6
DO - 10.1038/s41408-021-00484-6
M3 - Article
C2 - 34001853
AN - SCOPUS:85106231492
SN - 2044-5385
VL - 11
JO - Blood cancer journal
JF - Blood cancer journal
IS - 5
M1 - 93
ER -