CCL17 and neoplasm: Once established, tumor-derived factors drive macrophages toward an immunosuppressive phenotype which impairs anti-tumor T cell activity, primarily through the secretion of anti-inflammatory cytokines/chemokines such as TGF-β, IL-10, CCL17, and CCL22 (Biswas and Mantovani, 2010; Jackaman et al., 2017).