Functional characterization of human Cd33+ and Cd11b+ myeloid-derived suppressor cell subsets induced from peripheral blood mononuclear cells co-cultured with a diverse set of human tumor cell lines

J Transl Med. 2011 Jun 9;9:90. doi: 10.1186/1479-5876-9-90.


Background: Tumor immune tolerance can derive from the recruitment of suppressor cell populations, including myeloid-derived suppressor cells (MDSC). In cancer patients, MDSC accumulation correlates with increased tumor burden, but the mechanisms of MDSC induction remain poorly understood.

Methods: This study examined the ability of human tumor cell lines to induce MDSC from healthy donor PBMC using in vitro co-culture methods. These human MDSC were then characterized for morphology, phenotype, gene expression, and function.

Results: Of over 100 tumor cell lines examined, 45 generated canonical CD33+HLA-DR(low)Lineage- MDSC, with high frequency of induction by cervical, ovarian, colorectal, renal cell, and head and neck carcinoma cell lines. CD33+ MDSC could be induced by cancer cell lines from all tumor types with the notable exception of those derived from breast cancer (0/9, regardless of hormone and HER2 status). Upon further examination, these and others with infrequent CD33+ MDSC generation were found to induce a second subset characterized as CD11b+CD33(low)HLA-DR(low)Lineage-. Gene and protein expression, antibody neutralization, and cytokine-induction studies determined that the induction of CD33+ MDSC depended upon over-expression of IL-1β, IL-6, TNFα, VEGF, and GM-CSF, while CD11b+ MDSC induction correlated with over-expression of FLT3L and TGFβ. Morphologically, both CD33+ and CD11b+ MDSC subsets appeared as immature myeloid cells and had significantly up-regulated expression of iNOS, NADPH oxidase, and arginase-1 genes. Furthermore, increased expression of transcription factors HIF1α, STAT3, and C/EBPβ distinguished MDSC from normal counterparts.

Conclusions: These studies demonstrate the universal nature of MDSC induction by human solid tumors and characterize two distinct MDSC subsets: CD33+HLA-DR(low)HIF1α+/STAT3+ and CD11b+HLA-DR(low)C/EBPβ+, which should enable the development of novel diagnostic and therapeutic reagents for cancer immunotherapy.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Antigens, CD / metabolism*
  • Antigens, Differentiation, Myelomonocytic / metabolism*
  • CD11b Antigen / metabolism*
  • CD28 Antigens / metabolism
  • CD3 Complex / metabolism
  • Cell Line, Tumor
  • Cell Proliferation
  • Cell Shape
  • Coculture Techniques
  • Cytokines / metabolism
  • Female
  • Gene Expression Regulation
  • HLA-DR Antigens / metabolism
  • Humans
  • Leukocytes, Mononuclear / cytology*
  • Lymphocyte Activation / immunology
  • Male
  • Membrane Proteins / metabolism
  • Middle Aged
  • Models, Biological
  • Myeloid Cells / cytology*
  • Myeloid Cells / metabolism*
  • Phenotype
  • Sialic Acid Binding Ig-like Lectin 3
  • T-Lymphocytes / cytology
  • T-Lymphocytes / metabolism
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transforming Growth Factor beta / metabolism
  • Young Adult


  • Antigens, CD
  • Antigens, Differentiation, Myelomonocytic
  • CD11b Antigen
  • CD28 Antigens
  • CD3 Complex
  • CD33 protein, human
  • Cytokines
  • HLA-DR Antigens
  • Membrane Proteins
  • Sialic Acid Binding Ig-like Lectin 3
  • Transcription Factors
  • Transforming Growth Factor beta
  • flt3 ligand protein