The distribution of macrophages with a M1 or M2 phenotype in relation to prognosis and the molecular characteristics of colorectal cancer

PLoS One. 2012;7(10):e47045. doi: 10.1371/journal.pone.0047045. Epub 2012 Oct 15.


High macrophage infiltration has been correlated to improved survival in colorectal cancer (CRC). Tumor associated macrophages (TAMs) play complex roles in tumorigenesis since they are believed to hold both tumor preventing (M1 macrophages) and tumor promoting (M2 macrophages) activities. Here we have applied an immunohistochemical approach to determine the degree of infiltrating macrophages with a M1 or M2 phenotype in clinical specimens of CRC in relation to prognosis, both in CRC in general but also in subgroups of CRC defined by microsatellite instability (MSI) screening status and the CpG island methylator phenotype (CIMP). A total of 485 consecutive CRC specimens were stained for nitric oxide synthase 2 (NOS2) (also denoted iNOS) as a marker for the M1 macrophage phenotype and the scavenger receptor CD163 as a marker for the M2 macrophage phenotype. The average infiltration of NOS2 and CD163 expressing macrophages along the invasive tumor front was semi-quantitatively evaluated using a four-graded scale. Two subtypes of macrophages, displaying M1 (NOS2(+)) or M2 (CD163(+)) phenotypes, were recognized. We observed a significant correlation between the amount of NOS2(+) and CD163(+) cells (P<0.0001). A strong inverse correlation to tumor stage was found for both NOS2 (P<0.0001) and CD163 (P<0.0001) infiltration. Furthermore, patients harbouring tumors highly infiltrated by NOS2(+) cells had a significantly better prognosis than those infiltrated by few NOS2(+) cells, and this was found to be independent of MSI screening status and CIMP status. No significant difference was found on cancer-specific survival in groups of CRC with different NOS2/CD163 ratios. In conclusion, an increased infiltration of macrophages with a M1 phenotype at the tumor front is accompanied by a concomitant increase in macrophages with a M2 phenotype, and in a stage dependent manner correlated to a better prognosis in patients with CRC.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, CD / analysis
  • Antigens, CD / immunology*
  • Antigens, Differentiation, Myelomonocytic / analysis
  • Antigens, Differentiation, Myelomonocytic / immunology*
  • Colon / immunology
  • Colon / metabolism
  • Colon / pathology
  • Colorectal Neoplasms / diagnosis*
  • Colorectal Neoplasms / genetics
  • Colorectal Neoplasms / immunology
  • Colorectal Neoplasms / pathology
  • CpG Islands
  • DNA Methylation
  • Humans
  • Immunohistochemistry
  • Macrophages / immunology
  • Macrophages / metabolism
  • Macrophages / pathology*
  • Microsatellite Instability
  • Nitric Oxide Synthase Type II / analysis
  • Nitric Oxide Synthase Type II / immunology*
  • Phenotype
  • Prognosis
  • Receptors, Cell Surface / analysis
  • Receptors, Cell Surface / immunology*
  • Rectum / immunology
  • Rectum / metabolism
  • Rectum / pathology


  • Antigens, CD
  • Antigens, Differentiation, Myelomonocytic
  • CD163 antigen
  • Receptors, Cell Surface
  • NOS2 protein, human
  • Nitric Oxide Synthase Type II

Grant support

This study was supported by grants from the Swedish Cancer Society (grant no. CAN 2011/839, Palmqvist;, Swedish Research Council (grant no. B03488901, Palmqvist;, Cutting-Edge Research Grant from the County Council of Västerbotten, Sweden (grant no. VLL-132981, Palmqvist), Cancer Research Foundation in Northern Sweden (grant no. AMP 09-619, Edin;, and Tore Nilsons Foundation (Edin, The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.