Collective observations based on our studies (Asirvatham et al., 2006; Carey et al., 2009; Chaudhary et al., 2005; Patel et al., 2014, 2015; Sharma et al., 2012, 2013) led us to hypothesize that ID4 could be involved in selectively regulating AR activity through FKBP52 in prostate cancer. Here, FKBP4 is linked to prostate cancer.