Myeloid-derived suppressor cells have a central role in attenuated Listeria monocytogenes-based immunotherapy against metastatic breast cancer in young and old mice

Br J Cancer. 2013 Jun 11;108(11):2281-90. doi: 10.1038/bjc.2013.206. Epub 2013 May 2.


Background: Myeloid-derived suppressor cells (MDSCs) are present in large numbers in blood of mice and humans with cancer, and they strongly inhibit T-cell and natural killer (NK) cell responses, at young and old age. We found that a highly attenuated bacterium Listeria monocytogenes (Listeria(at))-infected MDSC and altered the immune-suppressing function of MDSC.

Methods: Young (3 months) and old (18 months) BALB/cByJ mice with metastatic breast cancer (4T1 model) were immunised with Listeria(at) semi-therapeutically (once before and twice after tumour development), and analysed for growth of metastases and primary tumour, in relation to MDSC-, CD8 T-cell and NK cell responses.

Results: We found that Listeria(at)-infected MDSC, which delivered Listeria(at) predominantly to the microenvironment of metastases and primary tumours, where they spread from MDSC into tumour cells (infected tumour cells will ultimately become a target for Listeria-activated immune cells). Immunotherapy with Listeria(at) significantly reduced the population of MDSC in blood and primary tumours, and converted a remaining subpopulation of MDSC into an immune-stimulating phenotype producing IL-12, in correlation with significantly improved T-cell and NK cell responses to Listeria(at) at both ages. This was accompanied with a dramatic reduction in the number of metastases and tumour growth at young and old age.

Conclusions: Although preclinical studies show that immunotherapy is less effective at old than at young age, our study demonstrates that Listeria(at)-based immunotherapy can be equally effective against metastatic breast cancer at both young and old age by targeting MDSC.

Publication types

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

MeSH terms

  • Age Factors
  • Animals
  • Female
  • Immunotherapy / methods
  • Interleukin-12 / biosynthesis
  • Interleukin-12 / immunology
  • Killer Cells, Natural / immunology
  • Killer Cells, Natural / microbiology
  • Listeria monocytogenes / immunology*
  • Mammary Neoplasms, Experimental / immunology
  • Mammary Neoplasms, Experimental / microbiology
  • Mammary Neoplasms, Experimental / therapy*
  • Mice
  • Mice, Inbred BALB C
  • Myeloid Cells / immunology
  • T-Lymphocytes / immunology
  • T-Lymphocytes / microbiology


  • Interleukin-12