CCL2 and neoplasm: Tumour derived exosomes enriched in immunosuppressive proteins including the chemokines/chemoattractant (CSF-1), monocyte chemoattractant protein-1/C-C chemokine 2 (MCP-1/CCL-2), and TGF-β, are also enhanced during hypoxia, leading to the macrophage recruitment and M2-like polarization both in vitro and in vivo [108].