Cell Reports
Volume 20, Issue 7, 15 August 2017, Pages 1654-1666
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Article
Pharmacologic or Genetic Targeting of Glutamine Synthetase Skews Macrophages toward an M1-like Phenotype and Inhibits Tumor Metastasis

https://doi.org/10.1016/j.celrep.2017.07.054Get rights and content
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Highlights

  • GS expression and activity are induced by M2 stimuli, especially under starvation

  • Inhibition of GS activity skews M2 macrophages toward an M1-like phenotype

  • Metabolic rewiring by GS loss favors immunostimulatory and antiangiogenic features

  • GS ablation in macrophages blocks vessels, immunosuppression, and metastasis

Summary

Glutamine-synthetase (GS), the glutamine-synthesizing enzyme from glutamate, controls important events, including the release of inflammatory mediators, mammalian target of rapamycin (mTOR) activation, and autophagy. However, its role in macrophages remains elusive. We report that pharmacologic inhibition of GS skews M2-polarized macrophages toward the M1-like phenotype, characterized by reduced intracellular glutamine and increased succinate with enhanced glucose flux through glycolysis, which could be partly related to HIF1α activation. As a result of these metabolic changes and HIF1α accumulation, GS-inhibited macrophages display an increased capacity to induce T cell recruitment, reduced T cell suppressive potential, and an impaired ability to foster endothelial cell branching or cancer cell motility. Genetic deletion of macrophagic GS in tumor-bearing mice promotes tumor vessel pruning, vascular normalization, accumulation of cytotoxic T cells, and metastasis inhibition. These data identify GS activity as mediator of the proangiogenic, immunosuppressive, and pro-metastatic function of M2-like macrophages and highlight the possibility of targeting this enzyme in the treatment of cancer metastasis.

Keywords

glutamine
glutamine synthetase
macrophages
succinate
HIF1α
metastasis
IL-10
starvation
metabolic rewiring

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12

These authors contributed equally

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