Myeloid derived suppressor cells (MDSC) are present in virtually all cancer patients, where they are induced and activated by inflammation. Because they are a major obstacle to immunotherapy of cancer, it is imperative to understand how these cells mediate their effects and communicate within the tumor microenvironment. The long-term objective of this collaborative program is to identify the molecules that MDSCs use to hijack the immune system and to use this information to re-program or neutralize MDSC. Preliminary evidence indicates that this intercellular communication is facilitated by exosomes, nanoscale membrane-bound vesicles shed by MDSC. We have identified several proteins in MDSC exosomes that have significant physiologic effects on other MDSC, and on macrophages, another population of myeloid cells that promote tumor growth. Preliminary experiments also indicate that proteins conjugated with ubiquitin chains are readily enriched from exosomes shed by MDSC. Protein modification by ubiquitination is a powerful signal, which is known to direct proteins to diverse cellular fates according to structural variations in te massive polyubiquitin tags. This multi-PI study will test the hypothesis that ubiquitinated protein in exosomes shed by MDSC and macrophages contribute to immune suppression. We will ask how ubiquitination marks cellular proteins for export as exosome cargo, and if ubiquitination is altered by inflammatory stimulation. Mass spectrometry has provided most of the information presently available about sites of ubiquitin conjugation on targeted proteins;however characterization of the linkages within ubiquitin chains remains a significant analytical challenge We will use novel synthetic methods to prepare polyubiquitins and proteins conjugated with polyubiquitins as standard reference compounds. We will use these standards to develop and test a proteomic strategy to characterize connection sites and their sequence in ubiquitin chains. This novel customized strategy, incorporating Asp-selective proteolysis, linkage-specific antibodies, LC-MS/MS and bioinformatics, will then be applied to characterize ubiquitin conjugates from exosomes shed by MDSC and macrophages. We will focus initially on chains with isopeptide bonds at K63, K48 and K11. These are considered to occur most frequently, have known functional correlations, and can be addressed by linkage-specific antibodies. Biological activity of selected ubiquitinated and other exosomal proteins will be validated by determining their ability to enhance pro-tumor activity and immune suppressive potency.

Public Health Relevance

Recently a family of cells has been shown to suppress the body's natural immune-response to tumor growth, and also to prevent the effectiveness of cancer immunotherapy. This project will characterize novel chemical signals by which suppressive myeloid cells control the immune- response, and provide new targets for intervention.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
Project #
Application #
Study Section
Enabling Bioanalytical and Imaging Technologies Study Section (EBIT)
Program Officer
Edmonds, Charles G
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Maryland College Park
Earth Sciences/Resources
College Park
United States
Zip Code
Rose, Rebecca L; Choksawangkarn, Waeowalee; Fenselau, Catherine (2018) Application of Higher Density Iron Oxide Nanoparticle Pellicles to Enrich the Plasma Membrane and Its Proteome from Cells in Suspension. Methods Mol Biol 1722:79-90
Ostrand-Rosenberg, Suzanne; Fenselau, Catherine (2018) Myeloid-Derived Suppressor Cells: Immune-Suppressive Cells That Impair Antitumor Immunity and Are Sculpted by Their Environment. J Immunol 200:422-431
Aebersold, Ruedi; Agar, Jeffrey N; Amster, I Jonathan et al. (2018) How many human proteoforms are there? Nat Chem Biol 14:206-214
Ostrand-Rosenberg, Suzanne (2018) Myeloid derived-suppressor cells: their role in cancer and obesity. Curr Opin Immunol 51:68-75
Adams, Katherine R; Chauhan, Sitara; Patel, Divya B et al. (2018) Ubiquitin Conjugation Probed by Inflammation in Myeloid-Derived Suppressor Cell Extracellular Vesicles. J Proteome Res 17:315-324
Chen, Dapeng; Gomes, Fabio; Abeykoon, Dulith et al. (2018) Top-Down Analysis of Branched Proteins Using Mass Spectrometry. Anal Chem 90:4032-4038
Geis-Asteggiante, LucĂ­a; Belew, Ashton T; Clements, Virginia K et al. (2018) Differential Content of Proteins, mRNAs, and miRNAs Suggests that MDSC and Their Exosomes May Mediate Distinct Immune Suppressive Functions. J Proteome Res 17:486-498
Horn, Lucas A; Long, Tiha M; Atkinson, Ryan et al. (2018) Soluble CD80 Protein Delays Tumor Growth and Promotes Tumor-Infiltrating Lymphocytes. Cancer Immunol Res 6:59-68
Singh, Rajesh K; Kazansky, Yaniv; Wathieu, Donald et al. (2017) Hydrophobic Patch of Ubiquitin is Important for its Optimal Activation by Ubiquitin Activating Enzyme E1. Anal Chem 89:7852-7860
Chauhan, Sitara; Danielson, Steven; Clements, Virginia et al. (2017) Surface Glycoproteins of Exosomes Shed by Myeloid-Derived Suppressor Cells Contribute to Function. J Proteome Res 16:238-246

Showing the most recent 10 out of 115 publications