E2F1 and Familial prostate cancer: Nevertheless, the expression of ID4 is epigenetically silenced in prostate cancer and, very recently, it has been demonstrated that ectopic over-expression of ID4 promotes cellular senescence in prostate cancer cell line DU145 by increasing the expression of p16, p21, p27, E-cadherin and vimentin, but down-regulating E2F1 expression.