Survival of the fittest: how myeloid-derived suppressor cells survive in the inhospitable tumor microenvironment

  • Suzanne Ostrand-RosenbergEmail author
  • Daniel W. Beury
  • Katherine H. Parker
  • Lucas A. Horn
Focussed Research Review


Myeloid-derived suppressor cells (MDSC) are present in most cancer patients where they are significant contributors to the immune suppressive tumor microenvironment (TME). The TME is a hostile locale due to deficiencies in oxygen (hypoxia) and nutrients, and the presence of reactive oxygen species (ROS). The survival of tumor cells within the TME is partially governed by two mechanisms: (1) Activation of the transcription factor Nuclear Factor Erythroid-derived 2-like 2 (Nrf2) which turns on genes that attenuate oxidative stress; and (2) The presence of High Mobility Group Box Protein-1 (HMGB1), a damage-associated molecular pattern molecule (DAMP) that induces autophagy and protects against apoptosis. Because Nrf2 and HMGB1 promote tumor cell survival, we speculated that Nrf2 and HMGB1 may facilitate MDSC survival. We tested this hypothesis using Nrf2+/+ and Nrf2−/− BALB/c and C57BL/6 mice and pharmacological inhibitors of HMGB1. In vitro and in vivo studies demonstrated that Nrf2 increased the suppressive potency and quantity of tumor-infiltrating MDSC by up-regulating MDSC production of H2O2 and decreasing MDSC apoptosis. Decreased apoptosis was accompanied by a decrease in the production of MDSC, demonstrating that MDSC levels are homeostatically regulated. Pharmacological inhibition of autophagy increased MDSC apoptosis, indicating that autophagy increases MDSC half-life. Inhibition of HMGB1 also increased MDSC apoptosis and reduced MDSC autophagy. These results combined with our previous findings that HMGB1 drives the accumulation of MDSC demonstrate that HMGB1 maintains MDSC viability by inducing autophagy. Collectively, these findings identify Nrf2 and HMGB1 as important factors that enable MDSC to survive in the TME.


MDSC Immune suppression Oxidative stress Autophagy High mobility group box protein 1 HMGB1 



Anti-oxidant response elements


Checkpoint blockade inhibitors


Cytotoxic T-lymphocyte-associated protein 4


Damage-associated molecular pattern


High mobility group box protein 1


Kelch-like ECH-associated protein 1


Myeloid-derived suppressor cells


Monocytic MDSC


Mammalian target of rapamycin


Nuclear factor erythroid-2-related factor 2


Programmed cell death protein 1


Programmed death-ligand 1


Propidium iodide


Polymorphonuclear or granulocytic MDSC


Receptor for advanced glycation endproducts


Reactive oxygen species


Tumor-infiltrating MDSC




Tumor microenvironment



The authors thank Ms. Virginia Clements for her outstanding technical support, and the undergraduate students at UMBC who participated in some of the original studies.

Author contributions

DWB, KHP, and LAH performed experiments. All authors developed the concepts, designed experiments, analyzed data, and wrote and edited the manuscript.


Original research described in this article was supported by US National Institutes of Health Grants R01CA84232, R01CA115880, and R01GM021248. Daniel W. Beury was partially supported by a US Department of Defense fellowship W81XWH-11-1-0115.

Compliance with ethical standards

Conflict of interest

The authors declare they have no conflict of interest.

Research involving animals

Original research described in this article was approved by the UMBC Institutional Animal Care and Use Committee, protocol #SO01691417.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of Biological SciencesUniversity of Maryland Baltimore County (UMBC)BaltimoreUSA
  2. 2.Department of PathologyUniversity of UtahSalt Lake CityUSA
  3. 3.Huntsman Cancer InstituteUniversity of UtahSalt Lake CityUSA

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