Many leukemia cells have elevated CXCR4 levels9, which allows them not only to acquire high ability of migration and invasion to targeted organs to cause tumor metastasis but also to home to the bone marrow to get favorable conditions for survival and growth in responses to CXCL12 secreted by stromal cells or endothelial cells in the microenvironment. The gene discussed is CXCL12; the disease is neoplasm.