Among 92 two GPCRs that have been implicated in the metastasis of breast cancer cells, CXCR4 is the possibly the best characterised, with a significant majority of published research describing the role of this receptor in metastasis, while there are many more that have had very few studies into their involvement in metastatic cancer such as NPY1R/5R or RXFP1. This evidence concerns the gene CXCR4 and breast cancer.