CCL2 and cancer: Adipocytes in the vicinity of BC tissue can be converted into cancer-associated adipocytes (CAAs), which promote cancer cell proliferation, enhance angiogenesis and change the extracellular matrix by secreting various cytokines such as IL-6, hepatocyte growth factor (HGF) and chemokine (C–C motif) ligand 2 (CCL2), playing an active role in the process of tumorigenesis and progression [9].