The role of macrophages during breast cancer development and response to chemotherapy

Macrophages play an important role in the immune system as a key host defense against pathogens. Non-polarized macrophages can differentiate into pro-inflammatory classical pathway-activated macrophages or anti-inflammatory alternative pathway-activated macrophages, both of which play central roles in breast cancer growth and progression in a process called polarization of macrophages. Classical pathway-activated and alternative pathway-activated macrophages can transform into each other and their transformational properties and orientation are determined by cytokines in the tumor microenvironment. Tumor-associated macrophages display many functions, such as tissue reforming, participating in inflammation and tumor growth in breast cancer progression. Some cytokines, such as interleukins and transcriptional activators, reside in the tumor microenvironment and influence tumor-associated macrophages. Chemotherapy is a common treatment for breast cancer and macrophages play an important role in mammary tumor cell migration, cancer invasion, and angiogenesis. This review summarizes the activities of tumor-associated macrophages in the mammary tumor, chemotherapeutic processes and some potential strategies for breast cancer therapy.