CCL2 and breast cancer: CAAs secrete more chemokine (C–C motif) ligand 2 (CCL2) [6], chemokine (C–C motif) ligand 5 (CCL5) [7], interleukin-1β (IL-1β), interleukin-6 (IL-6) [1], tumor necrosis factor-alpha (TNF-α), vascular endothelial growth factor (VEGF), leptin [8], etc., which can promote the invasion and metastasis of breast cancer (Fig. 1).