CXCR4 and breast cancer: The CXCR4 protein, a crucial G protein coupled receptor expressed on the cell membrane, exhibits high expression in TNBC compared to other subtypes of breast cancer, and is correlated with unfavorable prognostic outcomes.[16] Therefore, CXCR4 represents an optimal guidance target in TNBC and its small molecule inhibitor AMD3100 approved by FDA in 2008 is chosen to link to the nanoparticles.