HSP90AA1 and cancer: In cancer cells, Hsp90 is responsible for uncontrolled proliferation and apoptotic resistance by means of the regulation of several so-called clients, including steroid hormone receptors, kinases (e.g., Akt, Raf-1, Bcr-Abl, Cdk4, and Wee1), histone deacetylases (i.e., HDAC1 and HDAC6), and other oncogenic proteins [21,22].