title: Characterization of cytokine-induced myeloid-derived suppressor cells from normal human peripheral blood mononuclear cells.
abstract: Tumor immune tolerance can derive from the recruitment of suppressor cell populations, including myeloid-derived suppressor cells (MDSCs). In cancer patients, increased MDSCs correlate with more aggressive disease and a poor prognosis. Expression of 15 immune factors (TGFbeta, IL-1beta, IL-4, IL-6, IL-10, GM-CSF, M-CSF, IDO, fms-related tyrosine kinase 3 ligand, c-kit ligand, inducible NO synthase, arginase-1, TNF-alpha, cyclo-oxygenase 2, vascular endothelial growth factor [VEGF]) by MDSC-inducing human solid tumor cell lines was evaluated by RT-PCR. Based upon these data, cytokine mixtures were then tested for their ability to generate suppressive CD33(+) cells from healthy donor PBMCs in vitro by measuring their ability to inhibit the proliferation of, and IFN-gamma production by, fresh autologous human T cells after CD3/CD28 stimulation. Induced MDSCs were characterized with respect to their morphology, surface phenotype, and gene expression profile. MDSC-inducing cancer cell lines demonstrated multiple pathways for MDSC generation, including overexpression of IL-6, IL-1beta, cyclo-oxygenase 2, M-CSF, and IDO. CD33(+) cells with potent suppressive capacity were best generated in vitro by GM-CSF and IL-6, and secondarily by GM-CSF + IL-1beta, PGE(2), TNF-alpha, or VEGF. Characterization studies of cytokine-induced suppressive cells revealed CD33(+)CD11b(+)CD66b(+)HLA-DR(low)IL-13R alpha2(int) large mononuclear cells with abundant basophilic cytoplasm. Expression of inducible NO synthase, TGFbeta, NADPH oxidase, VEGF, and/or arginase-1 was also upregulated, and Transwell studies showed suppression of autologous T cells to be contact dependent. Suppressive CD33(+) cells generated from PBMCs by GM-CSF and IL-6 were consistent with human MDSCs. This study suggests that these cytokines are potential therapeutic targets for the inhibition of MDSC induction in cancer patients.
authors.affiliation: Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA.
authors.forename: Melissa G
authors.initials: MG
authors.lastname: Lechner
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Liebertz
authors.forename: Alan L
authors.initials: AL
authors.lastname: Epstein
mesh_terms: D015703:Antigens, CD / Q000378:metabolism*; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D018920:Coculture Techniques; D016207:Cytokines / Q000494:pharmacology*; D005434:Flow Cytometry; D020869:Gene Expression Profiling; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics; D006801:Humans; D016130:Immunophenotyping; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D022423:Myeloid Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009369:Neoplasms / Q000235:genetics / Q000473:pathology; D052247:Nitric Oxide Synthase Type II / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D063268:Sialic Acid Binding Ig-like Lectin 3; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics
chemical_list: D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; C571163:CD33 protein, human; D016207:Cytokines; D063268:Sialic Acid Binding Ig-like Lectin 3; D042461:Vascular Endothelial Growth Factor A; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D052247:Nitric Oxide Synthase Type II