CCL2 and hepatocellular carcinoma: Zhou et al found that TANs as a main source of CCL2 and CCL17 in HCC, which adsorbed the macrophages and CCR4+ Treg cells to the tumor tissue.19 In return, Spary et al identified CCL2 derived fibroblasts recruited the monocytes in prostate cancer.20 On the other hand, CCL2 induce the production of CCL3 in human and murine macrophages, which this CCL3-CCR1 axis promotes metastasis in the mouse model21 (Figure 1).