The interaction of CXCL12, which is secreted by bone marrow stromal cells including fibroblasts and endothelial cells, to C-X-C motif chemokine receptor 4 (CXCR4), which is aberrantly expressed in tumor cells, allows tumor cells to directionally migrate to bone [114] mainly through upregulating the two most crucial downstream pathways comprising IP3K and MAPK pathways. The gene discussed is CXCL12; the disease is neoplasm.