There are over 200 protein substrates of Hsp90 [2], many of which are the key factors in cancer development and progression, including tyrosine kinases (e.g., Src), serine-threonine kinases (e.g., Raf-1, AKT), cell cycle kinases (e.g., Wee1, POLO-1) [3,4], transcription factors (such as HIF-1), steroid receptors (e.g., estrogen, androgen, progesterone or glucocorticoid) and non-steroid receptors (e.g., HER2), as well as mutated forms of p53 [4,5]. This evidence concerns the gene HSP90AB1 and cancer.