CCL8 and neoplasm: MSC exposure to tissue growth factor-beta (TGF-β) [62] or challenging MSCs with monocyte chemotactic protein-1 (MCP-1), chemokine (C-C motif) ligand 8 (CCL-8), and/or interleukin 8 (IL-8) [71] can increase the migration of MSCs towards the tumor.