This is because Hsp90 is commonly overexpressed in prostate cancer compared to normal prostate cells (Cardillo and Ippoliti, 2006); prostate cancer cells are selectively sensitive to Hsp90-directed agents; and Hsp90 clients include the androgen receptor (Trepel et al., 2010), a major driver of prostate tumorigenesis. This evidence concerns the gene AR and Familial prostate cancer.