FKBP4 and Familial prostate cancer: Both natural and synthetic androgens can upregulate the expression of FKBP51 through AR binding to the enhancer region of the FKBP5 gene (Davies et al., 2005), suggesting that this may be an automatic regulatory pathway aimed at enhancing androgen sensitivity, which makes FKBP51 a potentially important factor in the etiology of prostate cancer (Maeda et al., 2022).