MDSCs mediate angiogenesis and predispose canine mammary tumor cells for metastasis via IL-28/IL-28RA (IFN-λ) signaling

PLoS One. 2014 Jul 30;9(7):e103249. doi: 10.1371/journal.pone.0103249. eCollection 2014.

Abstract

Background: Myeloid-derived suppressor cells (MDSCs) function in immunosuppression and tumor development by induction of angiogenesis in a STAT3-dependent manner. Knowledge of MDSC biology is mainly limited to mice studies, and more clinical investigations using spontaneous tumor models are required. Here we performed in vitro experiments and clinical data analysis obtained from canine patients.

Methods: Using microarrays we examined changes in gene expression in canine mammary cancer cells due to their co-culture with MDSCs. Further, using Real-time rt-PCR, Western blot, IHC, siRNA, angiogenesis assay and migration/invasion tests we examined a role of the most important signaling pathway.

Results: In dogs with mammary cancer, the number of circulating MDSCs increases with tumor clinical stage. Microarray analysis revealed that MDSCs had significantly altered molecular pathways in tumor cells in vitro. Particularly important was the detected increased activation of IL-28/IL-28RA (IFN-λ) signaling. The highest expression of IL-28 was observed in stage III/IV mammary tumor-bearing dogs. IL-28 secreted by MDSCs stimulates STAT3 in tumor cells, which results in increased expression of angiogenic factors and subsequent induction of angiogenesis by endothelial cells, epithelial-mesenchymal transition (EMT) and increased migration of tumor cells in vitro. Knockdown of IL-28RA decreased angiogenesis, tumor cell invasion and migration.

Conclusions: We showed for the first time that MDSCs secrete IL-28 (IFN-λ), which promotes angiogenesis, EMT, invasion and migration of tumor cells. Thus, IL-28 may constitute an interesting target for further therapies. Moreover, the similarity in circulating MDSC levels at various tumor clinical stages between canine and human patients indicates canines as a good model for clinical trials of drugs targeting MDSCs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Count
  • Cell Line, Tumor
  • Cell Movement
  • Coculture Techniques
  • Dogs
  • Epithelial-Mesenchymal Transition
  • Immunophenotyping
  • Interferon-gamma / metabolism*
  • Keratins / genetics
  • Keratins / metabolism
  • Mammary Neoplasms, Animal / genetics
  • Mammary Neoplasms, Animal / immunology
  • Mammary Neoplasms, Animal / metabolism*
  • Mammary Neoplasms, Animal / pathology*
  • Myeloid Cells / metabolism*
  • Neovascularization, Pathologic / immunology
  • Neovascularization, Pathologic / metabolism*
  • Receptors, Cytokine / metabolism*
  • Signal Transduction*
  • Vimentin / genetics
  • Vimentin / metabolism

Substances

  • Receptors, Cytokine
  • Vimentin
  • interleukin 28alpha receptor
  • Keratins
  • Interferon-gamma

Grant support

This work was supported by grant no. IP 2011027171 from the Ministry of Science and Higher Education and COST Action CM1106. JM was supported by ‘Mazovia’ fellowship. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.