Expression of the CXCR4 receptor, which is upregulated on cancer cells in both primary and metastatic tumors, mirrors that of CXCL12, suggesting that CXCR4-bearing cancer cells are actively guided by CXCL12 gradients to exit the primary tumor and metastasize to distant organs [12]. This evidence concerns the gene CXCR4 and metastatic neoplasm.