Of particular interest also is the fact that our analysis of the publicly available gene data sets showed that while individual expression levels of CXCR4 and CCR7 did not correlate with any breast tumour characteristics, CXCR4 and CCR7 co-expression was highly significantly linked to the tumour grade, further emphasizing the role of the interaction between the two receptors in breast cancer progression. This evidence concerns the gene CXCR4 and breast cancer.