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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.

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Citations
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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)....

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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....

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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....

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References
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Journal ArticleDOI
TL;DR: TT2 cells can serve as a valuable vehicle for the production of mutant mice by segregating inside the blastomeres, localized in an inner cell mass of blastocysts, and colonized efficiently in each tissue of the pups.

462 citations

Journal ArticleDOI
TL;DR: 4E-BP1 plays a prominent role in mediating the effects of these pathways in tumors in which they are activated by mutation, and provides mechanistic bases for the limited activity of AKT and MEK inhibitors in tumors with comutation of both pathways.

369 citations


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

  • ...Although previous studies reported that inhibition of 4E-BP phosphorylation is associated with the induction of apoptosis in tumors (39, 40), it was assumed that other molecules downstream of mTORC1 cooperatively contribute to AML propagation....

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Journal ArticleDOI
TL;DR: This work shows for two independent datasets that clinically observed BCR-ABL1 transcript dynamics during imatinib treatment of CML can consistently be explained by a selective functional effect ofImatinib on proliferative leukemia stem cells, and suggests the general potential of imatin ib to induce a complete elimination of the malignant clone.
Abstract: Treatment of chronic myeloid leukemia (CML) with the tyrosine kinase inhibitor imatinib represents a successful application of molecularly targeted cancer therapy. A rapid hematologic and cytogenetic response can be induced in the majority of people, even in advanced disease. However, complete eradication of malignant cells, which are characterized by the expression of the BCR-ABL1 fusion protein, is rare. Reasons for the persistence of the malignant clone are currently not known and provide a substantial challenge for clinicians and biologists. Based on a mathematical modeling approach that quantitatively explains a broad range of phenomena, we show for two independent datasets that clinically observed BCR-ABL1 transcript dynamics during imatinib treatment of CML can consistently be explained by a selective functional effect of imatinib on proliferative leukemia stem cells. Our results suggest the general potential of imatinib to induce a complete elimination of the malignant clone. Moreover, we predict that the therapeutic benefit of imatinib can, under certain circumstances, be accelerated by combination with proliferation-stimulating treatment strategies.

337 citations


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

  • ...This is illustrated by the case of chronic myeloid leukemia patients treated with tyrosine kinase inhibitors (37, 38)....

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Journal ArticleDOI
TL;DR: Enriched expression of LSC maintenance and ESC-like program genes in normal myeloid progenitors and poor-prognosis human malignancies links the frequency of aberrantly self-renewing progenitor-like cancer stem cells (CSCs) to prognosis in human cancer.

336 citations


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

  • ...are associated with stem cell phenotypes in AML is similar to that in HSCs or embryonic stem cells (18, 22, 23)....

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Journal ArticleDOI
TL;DR: Inhibiting the FKBP12/rapamycin-sensitive subset of mTOR functions in leukemic cells enhanced aerobic glycolysis and decreased uncoupled mitochondrial respiration within 25 min, as shown by the synergy between the glycoleytic inhibitor 2-deoxyglucose and rapamycin in decreasing cell viability.
Abstract: mTOR is a central regulator of cellular growth and metabolism. Using metabolic profiling and numerous small-molecule probes, we investigated whether mTOR affects immediate control over cellular metabolism by posttranslational mechanisms. Inhibiting the FKBP12/rapamycin-sensitive subset of mTOR functions in leukemic cells enhanced aerobic glycolysis and decreased uncoupled mitochondrial respiration within 25 min. mTOR is in a complex with the mitochondrial outer-membrane protein Bcl-xl and VDAC1. Bcl-xl, but not VDAC1, is a kinase substrate for mTOR in vitro, and mTOR regulates the association of Bcl-xl with mTOR. Inhibition of mTOR not only enhances aerobic glycolysis, but also induces a state of increased dependence on aerobic glycolysis in leukemic cells, as shown by the synergy between the glycolytic inhibitor 2-deoxyglucose and rapamycin in decreasing cell viability.

320 citations


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

  • ...In addition, mTORC1 regulates mitochondrial biogenesis (2, 3) and autophagy (4)....

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