ID4 and prostate cancer: 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.