CXCR4 and neoplasm: SDF-1α and its specific receptor CXCR4, which expressed on the membrane of tumor cells, form the SDF-1α/CXCR4 chemokine axis and play a pivotal role in migration, invasion and metastasis of some malignant tumors, such as melanoma, breast cancer and non-small cell lung cancer cells [27], [28].