Altered monocyte differentiation and macrophage polarization patterns in patients with breast cancer.

BACKGROUND: Macrophage heterogeneity is the main feature of the tumour microenvironment. Breast cancer is one of the most life-threatening cancers. However, macrophage polarization patterns in different tumour stages and the importance of its relationship to human epidermal growth factor receptor 2 (HER2) in breast cancer remains highly unclear. The present study investigated the patterns of monocyte differentiation and macrophage polarization in breast cancer.

METHODS: Patients with breast cancer (n = 48) and healthy controls (n = 39) were prospectively recruited. The percentages and subsets of circulating macrophage-like cells were analysed by flow cytometry, and the polarization patterns of these cells in the peripheral blood of patients with breast cancer were compared with those of healthy controls. In addition, macrophage polarization patterns in different stages and HER2 status in breast cancer were investigated.

RESULTS: The percentages of circulating macrophages, which are defined as PM-2 K+ cells in the peripheral blood, were significantly higher in patients with breast cancer than in healthy controls. The percentages of M1-like macrophages were significantly lower, but those of M2-like macrophages were significantly higher in patients with breast cancer than in healthy controls. The percentage of M2c-like macrophages was significantly higher in advanced (stages II and III) breast cancer. However, the patterns of macrophage polarization were not associated with HER2 status in breast cancer.

CONCLUSIONS: Aberrant macrophage polarization was observed in breast cancer and was correlated with breast cancer stage. These quantitative data may provide new molecular biomarkers and potential therapeutic targets in breast cancer.