CXCR4 and osteosarcoma: Studies show that CXCR4 plays an important role in metastasis of many cancers including breast [93-95], lung [96, 97], colorectal [98-100], gastric [101-103], ovarian [104, 105], prostate [106], pancreatic [107, 108], melanoma [100, 109-111], esophageal [112, 113], head and neck [114], bladder [115], osteosarcoma [116], neuroblastoma [117], glioblastoma [118, 119], and acute lymphoblastic leukemia [120].