Bone colonizing PC-3 cells induce the expression of active MMP-9 at earlier time periods suggesting that CXCL12/CXCR4-mediated homing of PC cells to bone would functionally link with the expression of MMP-9 in local bone tumor microenvironment and induce invasive bone tumor growth [5]. The gene discussed is CXCR4; the disease is bone neoplasm.