CCL5 and osteosarcoma: MSCs, in turn, stimulate the migration of osteosarcoma cells by C-C motif chemokine ligand 5 (CCL5)/RANTES secretion (Xu et al., 2009), thereby favoring the spread of cancer by providing metastatic osteosarcoma cells with a favorable microenvironment (Tsukamoto et al., 2012).