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Stem cell biology

Rictor has a pivotal role in maintaining quiescence as well as stemness of leukemia stem cells in MLL-driven leukemia

Abstract

Little is known about the roles of Rictor/mTORC2 in the leukemogenesis of acute myeloid leukemia. Here, we demonstrated that Rictor is essential for the maintenance of mixed lineage leukemia (MLL)-driven leukemia by preventing leukemia stem cells (LSCs) from exhaustion. Rictor depletion led to a reactive activation of mTORC1 signaling by facilitating the assembly of mTORC1. Hyperactivated mTORC1 signaling in turn drove LSCs into cycling, compromised the quiescence of LSCs and eventually exhausted their capacity to generate leukemia. At the same time, loss of Rictor had led to a reactive activation of FoxO3a in leukemia cells, which acts as negative feedback to restrain greater over-reactivation of mTORC1 activity and paradoxically protects leukemia cells from exhaustion. Simultaneous depletion of Rictor and FoxO3a enabled rapid exhaustion of MLL LSCs and a quick eradication of MLL leukemia. As such, our present findings highlighted a pivotal regulatory axis of Rictor-FoxO3a in maintaining quiescence and the stemness of LSCs.

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Acknowledgements

We thank Jiang J (Department of Developmental Biology, University of Texas Southwestern Medical Center at Dallas) for discussions and suggestions and Dr MA Magnuson from Vanderbilt University for providing the Rictorfl/fl mice. This work was supported in part by the ‘863’ Program (2012AA02A507) and ‘973’ Program (2012CB966604) of the China Ministry of Science and Technology; National Natural Science Funds of China (81025011, 81230052, 81090414, 81572565, 81500137).

Author contributions

Conception and design: Y Fang, Y Yang, JF Zhou. Development of methodology: Y Fang, Y Yang, CL Hua, M Zhou. Acquisition of data: Y Fang, Y Yang, CL Hua, SM Xu, HD Guo, N Wang, H Cheng. Analysis and interpretation of data (for example, statistical analysis, flow cytometry interpretation): Y Fang, Y Yang, CL Hua, SM Xu, XJ Zhao, L Huang, F Yu. Writing, review and/or revision of the manuscript: Y Fang, Y Yang, JF Zhou. Administrative, technical or material support: L Meng, T Cheng, Michael L Wang. Study supervision: WP Yuan, D Ma, JF Zhou.

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Correspondence to W Yuan, D Ma or J Zhou.

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Supplementary Information accompanies this paper on the Leukemia website

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Fang, Y., Yang, Y., Hua, C. et al. Rictor has a pivotal role in maintaining quiescence as well as stemness of leukemia stem cells in MLL-driven leukemia. Leukemia 31, 414–422 (2017). https://doi.org/10.1038/leu.2016.223

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