β2 adrenergic receptor–mediated signaling regulates the immunosuppressive potential of myeloid-derived suppressor cells
Hemn Mohammadpour, … , Scott I. Abrams, Elizabeth A. Repasky
Hemn Mohammadpour, … , Scott I. Abrams, Elizabeth A. Repasky
Published December 2, 2019; First published September 30, 2019
Citation Information: J Clin Invest. 2019;129(12):5537-5552. https://doi.org/10.1172/JCI129502.
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Categories: Research Article Immunology Oncology

β2 adrenergic receptor–mediated signaling regulates the immunosuppressive potential of myeloid-derived suppressor cells

Abstract

Catecholamines released by sympathetic nerves can activate adrenergic receptors present on nearly every cell type, including myeloid-derived suppressor cells (MDSCs). Using in vitro systems, murine tumor models in wild-type and genetically modified (β2-AR–/–) mice, and adoptive transfer approaches, we found that the degree of β2-AR signaling significantly influences MDSC frequency and survival in tumors and other tissues. It also modulates their expression of immunosuppressive molecules such as arginase-I and PD-L1 and alters their ability to suppress the proliferation of T cells. The regulatory functions of β2-AR signaling in MDSCs were also found to be dependent upon STAT3 phosphorylation. Moreover, we observed that the β2-AR–mediated increase in MDSC survival is dependent upon Fas-FasL interactions, and this is consistent with gene expression analyses, which reveal a greater expression of apoptosis-related genes in β2-AR–/– MDSCs. Our data reveal the potential of β2-AR signaling to increase the generation of MDSCs from both murine and human peripheral blood cells and that the immunosuppressive function of MDSCs can be mitigated by treatment with β-AR antagonists, or enhanced by β-AR agonists. This strongly supports the possibility that reducing stress-induced activation of β2-ARs could help to overcome immune suppression and enhance the efficacy of immunotherapy and other cancer therapies.

Authors

Hemn Mohammadpour, Cameron R. MacDonald, Guanxi Qiao, Minhui Chen, Bowen Dong, Bonnie L. Hylander, Philip L. McCarthy, Scott I. Abrams, Elizabeth A. Repasky

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Figure 6

Propranolol suppresses tumor growth and decreases MDSC accumulation in the spleen and tumor tissue.

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Propranolol suppresses tumor growth and decreases MDSC accumulation in t...
(A) Tumor growth kinetics in WT or β2-AR–/– mice orthotopically injected with 4T1 tumor cells receiving PBS or propranolol (i.p. daily injection) (n = 10). (B) Absolute number of MDSCs in spleen and tumor of WT mice treated with PBS or propranolol. (C) Tumor tissue was collected in WT 4T1 tumor–bearing mice at day 25 and stained for Gr-1 (×20 magnification), CD31 (×4 magnification), and VEGF-α (×10 magnification) (n = 5). (D) Representative flow cytometry plot of MDSCs in WT or β2-AR–/– 4T1 tumor–bearing mice receiving saline or 6-OHDA (50 mg/kg, i.p., weekly injection) (n = 6–10 mice from 2 replicates). (E) Percentage and absolute number of MDSCs in tumor and spleen of 4T1 tumor–bearing mice receiving saline or 6-OHDA (50 mg/kg, i.p., weekly injection) (n = 5). Two-way ANOVA was used to analyze statistical significance among tumor growth in different groups. These data are presented as mean ± SEM. Other data are presented as median ± minimum to maximum, and the Student’s t test was used to analyze statistical significance between 2 groups. In all panels, *P < 0.05, **P < 0.01, and ****P < 0.0001. A P value less than 0.05 was considered significant.