These variant ARs lack the ligand-binding domain (LBD) encoded by exons 5–8; however, many of them have been shown to be constitutively (AR-V3, -V4, -V7, and -V12) [5,14,15,16] or conditionally (AR-V1 and AR-V9) [5,15] active androgen-independent transcription factors in prostate cancer cells. The gene discussed is AR; the disease is prostate cancer.