CCL17 and breast cancer: CCL11 expression is induced by hypoxia in breast cancer cells to recruit CCR5+ macrophages,50 whereas CCL17 and CCL22 secreted by tumor cells, TAMs, and/or DCs can attract CCR4-expressing CD4+ Th17, Treg, and Th2 cells and monocytes with protumor or antitumor activities.51 Activin-A secretion by melanoma cells clearly stimulated tumor growth independently of CD4+ cells and IL-4.