To gain evidence of the link between ERG methylation and prostate cancer progression, we took advantage of the Pb-Cre4;Rosa26ERG/ERG (ERG mice) with prostate-specific expression of ERG and of the combined Pb-Cre4;Ptenflox/flox;Rosa26ERG/ERG (ERG/PTEN mice) with prostate-specific ERG expression and PTEN deletion. The gene discussed is ERG; the disease is prostate cancer.