HSP90AA1 and neoplasm: AHA1, as a co-chaperone of Hsp90, generally enhances the function of Hsp90 through the hydrolyzation of adenosine triphosphate (ATP) to stimulate the ATPase activity of Hsp90.10–12 AHA1 promotes effective folding of Hsp90-dependent client proteins, such as steroid receptors and many kinases involved in cellular signaling, including FKBP52 and p23/Sba1.10,13 In addition, AHA1 regulates the activity of Hsp90 and its client proteins to affect tumor progression through post-translational modifications.14