scispace - formally typeset
Search or ask a question
Journal ArticleDOI

mTORC1 is essential for leukemia propagation but not stem cell self-renewal

01 Jun 2012-Journal of Clinical Investigation (American Society for Clinical Investigation)-Vol. 122, Iss: 6, pp 2114-2129
TL;DR: Transplantation of Raptor-deficient undifferentiated AML cells in a limiting dilution revealed that mTORC1 is essential for leukemia initiation, and it was demonstrated that the reactivation of m TORC1 in those cells restored their leukemia-initiating capacity.
Abstract: Although dysregulation of mTOR complex 1 (mTORC1) promotes leukemogenesis, how mTORC1 affects established leukemia is unclear. We investigated the role of mTORC1 in mouse hematopoiesis using a mouse model of conditional deletion of Raptor, an essential component of mTORC1. Raptor deficiency impaired granulocyte and B cell development but did not alter survival or proliferation of hematopoietic progenitor cells. In a mouse model of acute myeloid leukemia (AML), Raptor deficiency significantly suppressed leukemia progression by causing apoptosis of differentiated, but not undifferentiated, leukemia cells. mTORC1 did not control cell cycle or cell growth in undifferentiated AML cells in vivo. Transplantation of Raptor-deficient undifferentiated AML cells in a limiting dilution revealed that mTORC1 is essential for leukemia initiation. Strikingly, a subset of AML cells with undifferentiated phenotypes survived long-term in the absence of mTORC1 activity. We further demonstrated that the reactivation of mTORC1 in those cells restored their leukemia-initiating capacity. Thus, AML cells lacking mTORC1 activity can self-renew as AML stem cells. Our findings provide mechanistic insight into how residual tumor cells circumvent anticancer therapies and drive tumor recurrence.

Content maybe subject to copyright    Report

Citations
More filters
Journal Article
TL;DR: Research data show that more resistant stem cells than common cancer cells exist in cancer patients, and to identify unrecognized differences between cancer stem cells and cancer cells might be able to develop effective classification, diagnose and treat for cancer.
Abstract: Stem cells are defined as cells able to both extensively self-renew and differentiate into progenitors. Research data show that more resistant stem cells than common cancer cells exist in cancer patients.To identify unrecognized differences between cancer stem cells and cancer cells might be able to develope effective classification,diagnose and treat ment for cancer.

2,194 citations

Journal ArticleDOI
TL;DR: It is shown that phosphorylation of the autophagy-adaptor protein p62 markedly increases p62's binding affinity for Keap1, an adaptor of the Cul3-ubiquitin E3 ligase complex responsible for degrading Nrf2, and that inhibitors of the interaction between phosphorylated p62 and Keap 1 have potential as therapeutic agents against human HCC.

824 citations


Cites background from "mTORC1 is essential for leukemia pr..."

  • ...Phosphorylation of p62 and induction of Nqo1 both decreased upon As(III) exposure in MEFs lacking Raptor (Hoshii et al., 2012), a component of the mTORC1 complex (Figures S2B and S2C)....

    [...]

Journal ArticleDOI
TL;DR: A comprehensive review of the current understanding of the mechanisms and regulation of autophagy in embryonic stem cells, several tissue stem cells (particularly hematopoietic stem cells), as well as a number of cancer stem cells is provided.
Abstract: Autophagy is a highly conserved cellular process by which cytoplasmic components are sequestered in autophagosomes and delivered to lysosomes for degradation. As a major intracellular degradation and recycling pathway, autophagy is crucial for maintaining cellular homeostasis as well as remodeling during normal development, and dysfunctions in autophagy have been associated with a variety of pathologies including cancer, inflammatory bowel disease and neurodegenerative disease. Stem cells are unique in their ability to self-renew and differentiate into various cells in the body, which are important in development, tissue renewal and a range of disease processes. Therefore, it is predicted that autophagy would be crucial for the quality control mechanisms and maintenance of cellular homeostasis in various stem cells given their relatively long life in the organisms. In contrast to the extensive body of knowledge available for somatic cells, the role of autophagy in the maintenance and function of stem cells is only beginning to be revealed as a result of recent studies. Here we provide a comprehensive review of the current understanding of the mechanisms and regulation of autophagy in embryonic stem cells, several tissue stem cells (particularly hematopoietic stem cells), as well as a number of cancer stem cells. We discuss how recent studies of different knockout mice models have defined the roles of various autophagy genes and related pathways in the regulation of the maintenance, expansion and differentiation of various stem cells. We also highlight the many unanswered questions that will help to drive further research at the intersection of autophagy and stem cell biology in the near future.

255 citations


Cites background from "mTORC1 is essential for leukemia pr..."

  • ...Conversely, the deletion of the MTORC1 component RAPTOR, therefore theoretically causing an increase in autophagy, results in a decrease of this myeloid population.(91) However, it remains to be shown definitively that loss or gain of autophagy contributes to this phenotype, as MTOR inhibition signals for many other important cellular functions such as inhibition of protein translation, mitochondrial biogenesis, cell growth, motility and proliferation....

    [...]

Journal ArticleDOI
14 Nov 2013-Blood
TL;DR: It is shown that glutamine removal inhibits mTORC1 and induces apoptosis in AML cells, and that l-ases upregulate glutamine synthase expression in leukemic cells and that a GS knockdown enhances l-ase-induced apoptotic response in someAML cells.

238 citations


Cites background from "mTORC1 is essential for leukemia pr..."

  • ...Recently, it was shown in a raptor deficiency mouse model thatmTORC1 inactivation induces apoptosis in differentiated leukemic cells and maintains immature leukemic cells with leukemia initiation potential in a dormant state, underlying the critical role of mTORC1 in leukemia.(4) In vitro, in primary AML cells, mTORC1 inhibition with rapamycin has cytostatic effects but does not induce apoptosis,(2-5) mainly because it does not inhibit 4E-BP1 phosphorylation on ser65....

    [...]

References
More filters
Journal ArticleDOI
01 Nov 2001-Nature
TL;DR: Stem cell biology has come of age: Unequivocal proof that stem cells exist in the haematopoietic system has given way to the prospective isolation of several tissue-specific stem and progenitor cells, the initial delineation of their properties and expressed genetic programmes, and the beginnings of their utility in regenerative medicine.
Abstract: Stem cell biology has come of age. Unequivocal proof that stem cells exist in the haematopoietic system has given way to the prospective isolation of several tissue-specific stem and progenitor cells, the initial delineation of their properties and expressed genetic programmes, and the beginnings of their utility in regenerative medicine. Perhaps the most important and useful property of stem cells is that of self-renewal. Through this property, striking parallels can be found between stem cells and cancer cells: tumours may often originate from the transformation of normal stem cells, similar signalling pathways may regulate self-renewal in stem cells and cancer cells, and cancer cells may include 'cancer stem cells' - rare cells with indefinite potential for self-renewal that drive tumorigenesis.

8,999 citations

Journal ArticleDOI
26 Jul 2002-Cell
TL;DR: It is reported that mTOR forms a stoichiometric complex with raptor, an evolutionarily conserved protein with at least two roles in the mTOR pathway that through its association with mTOR regulates cell size in response to nutrient levels.

2,902 citations


"mTORC1 is essential for leukemia pr..." refers result in this paper

  • ...Although mTORC1 reportedly controls cell size (cell growth) (34), we did not observe a decrease in the size of our Raptor-deficient AML cells (Figure 6B), and we found that the amount of protein per cell was comparable in control and Raptor-deficient AML stem cells (Figure 6, C and D)....

    [...]

Journal ArticleDOI
TL;DR: It is shown that rapamycin inhibits the assembly of mTORC2 and that, in many cell types, prolongedRapamycin treatment reduces the levels of m TORC2 below those needed to maintain Akt/PKB signaling.

2,621 citations


"mTORC1 is essential for leukemia pr..." refers background in this paper

  • ...We found that Raptor deficiency did not affect the expression level of Rictor, an essential component of mTORC2, but it is possible that long-term inactivation of mTORC1 in Raptordeficient AML cells affects the assembly and activity of mTORC2, leading to inhibition of AKT, in the same manner as prolonged rapamycin treatment (49)....

    [...]

  • ...On the other hand, prolonged rapamycin treatment is reported to suppress AKT via the disassembly of the mTORC2 complex in certain cell types (49)....

    [...]

Journal ArticleDOI
TL;DR: The data suggest that feedback down-regulation of receptor tyrosine kinase signaling is a frequent event in tumor cells with constitutive mTOR activation, and reversal of this feedback loop by rapamycin may attenuate its therapeutic effects, whereas combination therapy that ablates mTOR function and prevents Akt activation may have improved antitumor activity.
Abstract: Stimulation of the insulin and insulin-like growth factor I (IGF-I) receptor activates the phosphoinositide-3-kinase/Akt/mTOR pathway causing pleiotropic cellular effects including an mTOR-dependent loss in insulin receptor substrate-1 expression leading to feedback down-regulation of signaling through the pathway. In model systems, tumors exhibiting mutational activation of phosphoinositide-3-kinase/Akt kinase, a common event in cancers, are hypersensitive to mTOR inhibitors, including rapamycin. Despite the activity in model systems, in patients, mTOR inhibitors exhibit more modest antitumor activity. We now show that mTOR inhibition induces insulin receptor substrate-1 expression and abrogates feedback inhibition of the pathway, resulting in Akt activation both in cancer cell lines and in patient tumors treated with the rapamycin derivative, RAD001. IGF-I receptor inhibition prevents rapamycin-induced Akt activation and sensitizes tumor cells to inhibition of mTOR. In contrast, IGF-I reverses the antiproliferative effects of rapamycin in serum-free medium. The data suggest that feedback down-regulation of receptor tyrosine kinase signaling is a frequent event in tumor cells with constitutive mTOR activation. Reversal of this feedback loop by rapamycin may attenuate its therapeutic effects, whereas combination therapy that ablates mTOR function and prevents Akt activation may have improved antitumor activity.

2,423 citations


"mTORC1 is essential for leukemia pr..." refers background in this paper

  • ...org Volume 122 Number 6 June 2012 (32, 33), neither Raptor deficiency nor rapamycin resulted in hyperphosphorylation of AKT (S473) (Figure 6A and Supplemental Fig-...

    [...]

Journal ArticleDOI
TL;DR: Recent findings on the regulators and effectors of mTOR are highlighted and specific cases that serve as paradigms for the different modes of m TOR regulation and its control of translation are discussed.
Abstract: The process of translation requires substantial cellular resources. Cells have therefore evolved complex mechanisms to control overall protein synthesis as well as the translation of specific mRNAs that are crucial for cell growth and proliferation. At the heart of this process is the mammalian target of rapamycin (mTOR) signalling pathway, which senses and responds to nutrient availability, energy sufficiency, stress, hormones and mitogens to modulate protein synthesis. Here, we highlight recent findings on the regulators and effectors of mTOR and discuss specific cases that serve as paradigms for the different modes of mTOR regulation and its control of translation.

2,328 citations


"mTORC1 is essential for leukemia pr..." refers background in this paper

  • ...These target molecules control cell growth (size) and proliferation by modifying protein translation (1)....

    [...]