CXCR4 and neoplasm: The CXCL12‐ CXCR4 axis formed by the interplay between CXCL12 and its specific receptor CXCR4, and the paired axis plays an important role in modulating the immunity and inflammation response, whose function is thought as regulating the development and function of hematopoietic system and lymphatic system, and participating in the development of central nervous system and tumor [30].