It is worth noting that in luminal breast cancer cells, exposure to estradiol has no impact on total PAX2 mRNA and protein levels; in addition, total levels of PAX2 protein are comparable in luminal versus non-luminal breast cancer cells in vitro, similar to clinical data showing the presence of PAX2 in luminal as well as non-luminal tumours in vivo [14,15]. This evidence concerns the gene PAX2 and breast cancer.