Androgen receptor (AR) (NR3C4, nuclear receptor subfamily 3, group C, gene 4), a member of steroid hormone group of nuclear receptor superfamily, plays an essential role in the development and proliferation of prostate cancer (Tsai and O'Malley, 1994; Mangelsdorf et al., 1995; Nuclear Receptors Nomenclature Committee, 1999). The gene discussed is AR; the disease is Familial prostate cancer.