There is current interest in high affinity antagonists which bind to the CXCR4 receptor to prevent HIV entry and/or abrogate CXCL12 signalling.13 Preventing CXCL12-initiated CXCR4 signalling has resulted in a reduction in tumour growth, metastasis inhibition and increase in sensitivity to standard therapies in breast cancer, pancreatic cancer and gliomas.14–16 AMD3100 (PlerixaforTM) is a cyclam-based CXCR4 antagonist which is used clinically, in combination with G-CSF, as a hematopoietic stem cell mobilization agent. This evidence concerns the gene CXCR4 and breast cancer.