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

• Published in: Leukemia 2017-02, Vol.31 (2), p.414-422
• Main Authors: Fang, Y, Yang, Y, Hua, C, Xu, S, Zhou, M, Guo, H, Wang, N, Zhao, X, Huang, L, Yu, F, Cheng, H, Wang, M L, Meng, L, Cheng, T, Yuan, W, Ma, D, Zhou, J
• Format: Article
• Language: English
• Subjects: 13/1; 13/31; 631/532/2443; 631/67/71; 64/60; 692/308/2171; 692/699/67/1990/283; Acute myeloid leukemia; Analysis; Animals; Biology; Cancer Research; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cell Line; Cell Self Renewal - genetics; Cell Survival - genetics; Cell Transformation, Neoplastic; Cells (Biology); Cluster Analysis; Critical Care Medicine; Depletion; Epigenetics; Forkhead Box Protein O3 - genetics; Forkhead Box Protein O3 - metabolism; FOXO3 protein; Gene Expression Profiling; Gene Knockdown Techniques; Genetic aspects; Health aspects; Hematology; Hospitals; Intensive; Internal Medicine; Leukemia; Leukemia, Myeloid, Acute - genetics; Leukemia, Myeloid, Acute - metabolism; Leukemogenesis; Mechanistic Target of Rapamycin Complex 1; Medical schools; Medicine; Medicine & Public Health; Mice; Mice, Knockout; Multiprotein Complexes - metabolism; Negative feedback; Neoplastic Stem Cells - metabolism; Oncology; original-article; Rapamycin-Insensitive Companion of mTOR Protein; Resting Phase, Cell Cycle - genetics; Roles; Signal Transduction; Signaling; Stem cells; TOR Serine-Threonine Kinases - metabolism
• ISSN: 0887-6924; 1476-5551
• DOI: 10.1038/leu.2016.223

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.