The effect of Id4 leading to decreased proliferation and S-phase arrest in DU145 prostate cancer cell line may be due to increase in the expression of tumor suppressors E-cadherin, p27, p21 and the bHLH transcription factors E12/E47 [64-67] and/or activation of previously silenced tumor suppressors. The gene discussed is CDKN1A; the disease is prostate cancer.