CD4 and breast cancer: Among many examples of these chemokines’ activities, CXCL2 and CCL2 have been shown to recruit myeloid-derived suppressor cells (MDSC) [39, 40]; CCL2 and CCL5 have been implicated in recruitment of tumor-supporting macrophages [41-43]; CCL5 has been shown to have direct pro-tumorigenic activity in metastatic colon cancer [44]; CCL18 induces epithelial-mesenchymal transition in breast cancer [45]; and CCL20 recruits IL-22-producing CD4+ T cells that contribute to tumorigenesis in colon cancer [46].