Herein, we showed that LXR-α acts as a tumor suppressor in prostate cancer with the following lines of supporting evidence: (1) LXR-α is down-regulated in prostate cancer tissues and high levels of LXR-α predicts a biomarker for prostate cancer; (2) Overexpression of LXR-α significantly inhibits the growth and metastasis of prostate cancer cells; and (3) The tumor suppressor function of LXR-α is mediated by the accumulation of the bona fide tumor suppressors, including p21 and p27. The gene discussed is NR1H3; the disease is prostate carcinoma.