In addition, GST-NT21MP, which is a synthetic 21-mer peptide antagonist of CXCR4 (NT21MP) derived from the viral macrophage inflammatory protein II, was found to block the CXCR4 pathway, thus decreasing SDF-1-induced cell growth, adhesion and migration capacities in breast cancer cell lines [123]. Here, CXCR4 is linked to breast cancer.