CXCR4 and osteosarcoma: The molecular characterization of primary cultures of CSCs isolated from post-surgery canine osteosarcoma specimens as well as by immunohistochemistry from tumor fixed sections, has highlighted analogies with humans on the overexpression of chemokine receptor type 4 (CXCR4) and its chemokine ligand type 12 (CXCL12) [43].