Effect of macrophages on breast cancer cell proliferation, and on expression of hormone receptors, uPAR and HER-2

Malignant tumors, including breast cancers, are frequently infiltrated with innate immune cells and tumor-associated macrophages (TAMs) represent the major inflammatory component in stroma of many tumors. In this study, we examined the immunoreactivity of the macrophage markers CD68 and CD163 as well as the hormone receptors estrogen receptor α (ERα), progesterone receptor (PR), estrogen receptor β1 (ERβ1), human epidermal growth factor receptor 2 (HER-2), matrix metalloproteinase 9 (MMP-9), urokinase-type plasminogen activator receptor (uPAR) and the proliferations marker Ki67 in 17 breast cancer biopsies. The quantitative score for CD68(+) and CD163(+) strongly indicate M2 phenotype dominance in the currently investigated biopsies. We found that an increasing level of macrophages was negatively associated with ERα or PR, whereas a positive association was observed for Ki-67 or uPAR. No significant association could be seen between the level of macrophage and HER-2, ERβ1 or MMP-9 expression. Effect of conditioned media (CM) generated from cultured human M1 and M2 macrophage phenotypes were investigated on the proliferation and expression of selected markers in the T47D breast cancer cell line. We found that in contrast to the in vivo situation, in particularly the CM from M1 macrophages decreased the growth and Ki67 expression in T47D, and significantly increased ERβ1 mRNA levels. Moreover, in accordance to the in vivo situation the CM from the macrophages decreased the expression of ERα protein as well as ERα or PR mRNA. In conclusion our results show that macrophages alone have the capability to decrease the tumor cell expression of ERα and PR in vitro. In the tumor environment in vivo macrophages also contribute to an increase in tumor cell expression of uPAR and Ki67, suggesting that macrophages are involved in impairing the prognosis for breast cancer patients.