CCL17 and cancer: Unlike M2 macrophages, M1→M2 began to secrete certain IL-4-induced chemokines only after co-culture with cancer cell spheroids, for instance, CCL17 (M1→M2: 0.02 ng/mL; S + M1→M2: 0.12 ng/mL, p = 0.0004) and CCL24 (M1→M2: 0.5 ng/mL; S + M1→M2: 2.4 ng/mL, p = 0.0016) (Figure 6).