Remarkably, although their functional interactions with ERα clearly differ, the activities of these three HOX proteins, HOXA1, HOXB7, and HOXB13, have been linked to Tamoxifen resistance and poor prognosis of breast cancer (51, 78–80), most probably reflecting roles in different cancer cell processes, possibly at different stages of tumor development. This evidence concerns the gene HOXB13 and breast carcinoma.