Targeting glutamine metabolism enhances tumor-specific immunity by modulating suppressive myeloid cells
Min-Hee Oh, … , Maureen R. Horton, Jonathan D. Powell
Min-Hee Oh, … , Maureen R. Horton, Jonathan D. Powell
Published April 23, 2020
Citation Information: J Clin Invest. 2020;130(7):3865-3884. https://doi.org/10.1172/JCI131859.
View: Text | PDF
Research Article Immunology Oncology

Targeting glutamine metabolism enhances tumor-specific immunity by modulating suppressive myeloid cells

Abstract

Myeloid cells comprise a major component of the tumor microenvironment (TME) that promotes tumor growth and immune evasion. By employing a small-molecule inhibitor of glutamine metabolism, not only were we able to inhibit tumor growth, but we markedly inhibited the generation and recruitment of myeloid-derived suppressor cells (MDSCs). Targeting tumor glutamine metabolism led to a decrease in CSF3 and hence recruitment of MDSCs as well as immunogenic cell death, leading to an increase in inflammatory tumor-associated macrophages (TAMs). Alternatively, inhibiting glutamine metabolism of the MDSCs themselves led to activation-induced cell death and conversion of MDSCs to inflammatory macrophages. Surprisingly, blocking glutamine metabolism also inhibited IDO expression of both the tumor and myeloid-derived cells, leading to a marked decrease in kynurenine levels. This in turn inhibited the development of metastasis and further enhanced antitumor immunity. Indeed, targeting glutamine metabolism rendered checkpoint blockade–resistant tumors susceptible to immunotherapy. Overall, our studies define an intimate interplay between the unique metabolism of tumors and the metabolism of suppressive immune cells.

Authors

Min-Hee Oh, Im-Hong Sun, Liang Zhao, Robert D. Leone, Im-Meng Sun, Wei Xu, Samuel L. Collins, Ada J. Tam, Richard L. Blosser, Chirag H. Patel, Judson M. Englert, Matthew L. Arwood, Jiayu Wen, Yee Chan-Li, Lukáš Tenora, Pavel Majer, Rana Rais, Barbara S. Slusher, Maureen R. Horton, Jonathan D. Powell

×

Figure 3

Glutamine antagonism reduces MDSCs by increasing cell death and inhibiting tumor CSF3 secretion.

Options: View larger image (or click on image) Download as PowerPoint
Glutamine antagonism reduces MDSCs by increasing cell death and inhibiti...
(A) MDSCs from 4T1 tumor–bearing mice were treated with DON (1 μM) for 24 hours, and the active caspase-3 level was analyzed by immunoblot. Actin was used as loading control. (B–D) 4T1 tumor–bearing mice were treated with JHU083 (1 mg/kg) starting on day 14 after tumor inoculation. (B) After 7 hours of the first treatment and following every daily treatment, active caspase-3 on PMN-MDSCs and Mo-MDSCs from blood was analyzed by flow cytometry at the indicated time points (n = 5/group). (C) Cell numbers and percentages of MDSCs from tumor-infiltrating leukocytes (TIL) were counted and analyzed by flow cytometry (n = 5/group). (D) Serum (n = 16/group) and tumors (n = 4/group) were collected from 4T1 tumor–bearing mice and CSF3 was measured by ELISA (top). After 6 hours of treatment with or without DON (1 μM), Csf3 mRNA levels were measured in 4T1 cells (bottom left) (n = 3 technical replicates). Csf3 mRNA levels were measured from in vivo 4T1 tumor lysates by q-PCR (n = 5 mice) (bottom right). (E) Percentages of PMN-MDSCs and Mo-MDSCs from empty vector (EV) 4T1 or CSF3-overexpressing (OE) 4T1 tumor–bearing mice were analyzed by flow cytometry. (F) C/EBPβ levels were measured by immunoblotting of GFP+ sorted tumor cells from 4T1 tumor–bearing mice (left) and 4T1 tumor cells with or without DON (1 μM) treated for 24 hours (right). (G) PMN-MDSCs and Mo-MDSCs from EV 4T1 or C/EBPβ-OE 4T1 tumor–bearing mice were analyzed by flow cytometry. Data are representative of at least 2 (E–G) or 3 (A–D) independent experiments and are presented as the mean ± SD. NS, not significant. *P < 0.05; **P < 0.01; ***P < 0.005; ****P < 0.001 by 2-way ANOVA with post hoc multiple t tests (B, C, E, and G) or unpaired t test (D).