Targeting glutamine uptake in AML.

Abstract : Cancer cells require nutrients and energy to adapt to increased biosynthetic activity and depend on mitochondrial oxidative phosphorylation (OXPHOS) and glycolysis. Whereas they exhibit a pronounced Warburg effect, their TCA cycle remains intact and becomes more dependent on glutamine metabolism through glutaminolysis[1]. Besides this role, intracellular glutamine is also essential for mTORC1 activation by leucine[2]. Many upstream signals regulate mTORC1 activation. Among them, a major process is the availability of leucine, which is required to activate the Rag (for Ras-related GTPases) proteins that enable the proper localization of mTORC1 at the lysosome surface close to its activator Rheb[3]. Leucine uptake into the cells is regulated by the bidirectional transporter SLC7A5/3A2, in exchange for glutamine. The level of leucine thereby depends on the intracellular glutamine concentrations, which is mainly mediated by the high affinity transporter SLC1A5. Thus, the cellular uptake and subsequent rapid efflux of glutamine in the presence of leucine make glutamine availability a limiting step for the activation of mTORC1. MTORC1 positively regulates protein translation through phosphorylation of protein S6 Kinase (P70S6K) and eukaryotic initiation factor 4E (eIF4E)-binding protein 1 (4E-BP1). Protein synthesis is controlled by the translational repressor 4E-BP1 whose phosphorylation at serine 65 is required to initiate the formation of the translation initiation complex. The dependence of acute myeloid leukemia (AML) cells to glutamine is little studied. In a recent work, we have tested the effects of glutamine depletion in AML cells[4]: leukemic cells are sensitive to glutamine removal leading to mTORC1 inhibition and apoptosis. The drug L-asparaginase (L-ase) also inhibits mTORC1 activity in AML cells, suppresses protein synthesis and induces apoptosis. The anti-leukemic effects of the two clinically available forms of L-ase, E Coli L-ase (Kidrolase®) and E. Chrysanthemi L-ase (Erwiniase®) are not mediated by the asparaginase activity of the enzyme. L-ases have also a glutaminase activity and transform extracellular glutamine into glutamate. Both L-ases induce dose and time-dependent mTORC1-inhibition which correlates with extra-cellular glutamine depletion[4]. Downstream of mTORC1, L-ase suppresses 4E-BP1 phosphorylation and inhibits [S 35
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Oncoscience, US National Library of Medicine, 2014, 1 ((1)), pp.1-2. eCollection 2014
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Nathalie Jacque, Didier Bouscary. Targeting glutamine uptake in AML.. Oncoscience, US National Library of Medicine, 2014, 1 ((1)), pp.1-2. eCollection 2014. 〈inserm-01158974〉

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