Overexpression of SIRT1 has been detected in diverse primary solid tumors and hematopoietic malignancies of the breast, colon, prostate, liver and also some types of leukemia [8,13,14,15], while loss of SIRT1 in Sirt1−/− mice is associated with smaller prostates that exhibited a morphologic phenotype similar to that commonly observed within PIN lesions [4]. The gene discussed is SIRT1; the disease is prostate intraepithelial neoplasia.