The Distribution of Macrophages with a M1 or M2 Phenotype in Relation to Prognosis and the Molecular Characteristics of Colorectal Cancer

Abstract

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.

Influenza virus replication in macrophages: balancing protection and pathogenesis

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Extracellular HSP110 skews macrophage polarization in colorectal cancer

“…In general, tumor-associated macrophages can be found within or surrounding various tumors, where they either promote tumor progression, angiogenesis, migration of tumor cells and T helper 2 responses (so-called M2 or alternative macrophages), or, conversely, they promote resistance to tumors, inflammatory responses and T helper 1 responses (so-called M1 or classical macrophages). 15,16 Although macrophages have been found in colorectal tumor sections, 17,18 the correlation of their abundance with the prognosis of MSI neoplasms is not yet clear.…”

PLD4 promotes M1 macrophages to perform antitumor effects in colon cancer cells

“…TAMs have been shown to be highly plastic cells that can display both tumor preventing (M1 macrophages) and tumor promoting functions (M2 macrophages) (9,10). further studied on the distribution of M1 and M2 macrophage phenotypes in colorectal cancers showed that patients who had high numbers of infiltrating M1 macrophages obtained a significantly better prognosis (11). M1 macrophages stimulated cell-mediated responses via secreting pro-inflammatory cytokines such as IL-1, IL-6, IL-12, IL-23 and TNf-α.…”