Using samples from breast cancer patients, we found that AhR is frequently over-expressed in ER-negative human breast tumors, and this is closely correlated with elevated expression of the NF-кB subunit RelB and inflammatory markers such as IL-8 (CXCL1 in mouse) and COX-2 (Vogel et al., 2011). This evidence concerns the gene CXCL1 and breast cancer.