AR and prostate cancer: Although the AR AF-2 can bind to a restricted set of LxxLL motifs (Ding et al. 1998; He et al. 1999; Needham et al. 2000) and is relatively potent (Wang et al. 2001), it usually displays weak independent activity at typical androgen-regulated genes, with significant activity observed only in the presence of high levels of p160 coactivators, as detected in some prostate cancers (He et al. 1999; Gregory et al. 2001).