Tumor-associated macrophages recruit CCR6+ regulatory T cells and promote the development of colorectal cancer via enhancing CCL20 production in mice

PLoS One. 2011 Apr 29;6(4):e19495. doi: 10.1371/journal.pone.0019495.


Background: Tumor-associated macrophages (TAMs) remodel the colorectal cancer (CRC) microenvironment. Yet, findings on the role of TAMs in CRC seem to be contradictory compared with other cancers. FoxP3(+) regulatory T (Treg)-cells dominantly infiltrate CRC. However, the underlying molecular mechanism in which TAMs may contribute to the trafficking of Treg-cells to the tumor mass remains unknown.

Methodology/principal findings: CRC was either induced by N-methyl-N-nitrosourea (MNU) and H. pylori or established by subcutaneous injection of mouse colorectal tumor cell line (CMT93) in mice. CMT93 cells were co-cultured with primary macrophages in a transwell apparatus. Recruitment of FoxP3 green fluorescence protein positive (FoxP3(GFP+)) Treg-cells was assessed using the IVIS Imaging System or immunofluorescence staining. A role for macrophages in trafficking of Treg-cells and in the development of CRC was investigated in CD11b diphtheria toxin receptor (CD11b-DTR) transgenic C57BL/6J mice in which macrophages can be selectively depleted. Treg-cells remarkably infiltrated solid tumor, and predominantly expressed the homing chemokine receptor (CCR) 6 in the induced CRC model. Both CMT93 cancer cells and macrophages produced a large amount of CCL20, the sole ligand of CCR6 in vitro and in vivo. Injection of recombinant mouse CCL20 into tumor sites promoted its development with a marked recruitment of Treg-cells in the graft CRC model. Conditional macrophage ablation decreased CCL20 levels, blocked Treg-cell recruitment and inhibited tumor growth in CD11b-DTR mice grafted with CMT93.

Conclusions/significance: TAMs recruit CCR6(+) Treg-cells to tumor mass and promote its development via enhancing the production of CCL20 in a CRC mouse model.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CD11b Antigen / biosynthesis
  • Chemokine CCL20 / metabolism*
  • Female
  • Forkhead Transcription Factors / biosynthesis
  • Green Fluorescent Proteins / metabolism
  • Helicobacter pylori / metabolism
  • Lymphocytes, Tumor-Infiltrating / cytology
  • Macrophages / cytology*
  • Macrophages / metabolism
  • Methylnitrosourea / pharmacology
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Microscopy, Fluorescence / methods
  • Receptors, CCR6 / biosynthesis*
  • T-Lymphocytes, Regulatory / cytology*


  • CCL20 protein, mouse
  • CCR6 protein, mouse
  • CD11b Antigen
  • Chemokine CCL20
  • Forkhead Transcription Factors
  • Foxp3 protein, mouse
  • Receptors, CCR6
  • Green Fluorescent Proteins
  • Methylnitrosourea