Our present functional analysis characterized that HNF4α could perform a tumor suppressor function in prostate cancer, as evidenced by its overexpression could induce cell-cycle arrest and cellular senescence in prostatic epithelial and prostate cancer cells, and conversely its knockdown could confer resistance to either oncogene-induced or drug-induced cellular senescence in prostatic cells. The gene discussed is HNF4A; the disease is Familial prostate cancer.