However, even with these limitations, many of the findings discussed have been validated by the fact that the same chemokine systems appear to be involved in mediating bone metastasis regardless of the cancer of origin, in particular CCL2/CCR2, CCL3/CCR1, IL-8/CXCR1, and CXCL12/CXCR4. This evidence concerns the gene CXCL12 and cancer.