This review summarizes the downstream cell signaling transduction of CXCL12/CXCR4/CXCR7 axis (abbreviation: CXCL12 axis) and the role of CXCL12 axis in tumor progression, growth, survival, angiogenesis, metastasis, and chemoresistance. The gene discussed is CXCR4; the disease is neoplasm.