MMPs have been shown to be involved in the metastatic growth of prostate tumors in the bone and also appear to be activated at earlier time periods of tumor growth [14]; therefore, these data provide a mechanistic connection between “homing” of cancer cells to distant sites mediated by CXCL12/CXCR4 axis and followed by expression of MMPs which mediate invasion and proliferation. The gene discussed is CXCR4; the disease is neoplasm.