Importantly, some studies have shown that the overexpression of Hsp90β in breast cancer, as part of a set of proteins involved in regulating estrogen receptor α activity, correlates with adverse clinical outcomes [10]; a variety of Hsp90 inhibitors are in clinical trials for breast cancer treatment [11], further highlighting the potential of Hsp90 as a therapeutic target. This evidence concerns the gene HSP90AA1 and breast cancer.