Interestingly, significant positive correlation between CXCR7 and CXCL12 gene expression (Pearson = 0.3, p = 2.0 × 10–16) was observed in breast cancer patients, suggesting a biological role for the CXCR7/CXCL12 genetic circuit in breast cancer biology. The gene discussed is CXCL12; the disease is breast cancer.