CXCR4, a G-protein-coupled receptor for the CXCL12 homeostatic chemokine promoting cell trafficking including the colonization of hematopoietic stem cells in bone marrow67, the homing of tumor cell to organs with high levels of CXCL12 (e.g. lymph nodes, lungs, liver, and bone marrow), and bone metastasis in PCa52,53, indeed mediates the function of Ac-KLF5 in osteoclastogenesis and bone metastaticlesion. The gene discussed is CXCR4; the disease is neoplasm.