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Blood. 2019 May 17. pii: blood.2019898114. doi: 10.1182/blood.2019898114. [Epub ahead of print]

Cysteine depletion targets leukemia stem cells through inhibition of electron transport complex II.

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Medicine, University of Colorado, Medical School, United States.
Hematology, University of Colorado Anschutz Medical Campus, United States.
of Biochemistry and Molecular Genetics, University of Colorado Denver, United States.
University of Colorado, United States.
University of Colorado Denver, United States.
Medicine, University of Colorado Denver Anschutz Medical Campus, United States.
Medicine, University of Colorado, United States


We have previously demonstrated that oxidative phosphorylation is required for the survival of human leukemia stem cells (LSCs) from acute myeloid leukemia (AML) patients. More recently, we demonstrated that LSCs in de novo AML patients rely on amino acid metabolism to drive oxidative phosphorylation. Notably, while overall levels of amino acids contribute to LSC energy metabolism, our current findings suggest that cysteine may be of particular importance for LSC survival. We demonstrate that exogenous cysteine is metabolized exclusively to glutathione. Upon cysteine depletion, glutathione synthesis is impaired, leading to reduced glutathionylation of succinate dehydrogenase A (SDHA), a key component of electron transport chain complex (ETC) II. Loss of SDHA glutathionylation impairs ETC II activity, thereby inhibiting oxidative phosphorylation, reducing production of ATP and leading to LSC death. Given the role of cysteine in driving LSC energy production we tested cysteine depletion as a potential therapeutic strategy. Using a novel cysteine-degrading enzyme we demonstrate selective eradication of LSCs, with no detectable effect on normal hematopoietic stem/progenitor cells. Together, these findings indicate that LSCs are aberrantly reliant on cysteine to sustain energy metabolism and that targeting this axis may represent a useful therapeutic strategy.


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