In addition to MCP-1, GM-CSF selectively upregulated the expression of other genes by macrophages whose products play an important role in the development of breast cancer, including CCL17 and tumor necrosis factor superfamily member 11 (TNFSF11; also known as RANKL) by recruiting Tregs [8] and facilitating mammary tumorigenesis [9], respectively. Here, CCL17 is linked to breast cancer.