CCL2 and neoplasm: Activation of macrophages by tumor-derived exosomes regulates tumor invasion and metastasis through reducing the release of tissue inhibitor of metalloproteinase-1 (TIMP1), IFNγ, and interleukin-16 (IL-16), and by increasing secretion of IL-8, C-C motif ligand 2 (CCL2), major intrinsic proteins (MIPs), and interleukin-1 receptor antagonist (IL-1Ra).