SIRT1 and neoplasm: SIRT1 was considered as both a tumor suppressor and a tumor promoter.52 SIRT1 inhibits expression and/or the activity of several oncogenes, leading to reduced cell proliferation, increased apoptosis and tumor suppression.53, 54 In response to DNA damage, SIRT1 promotes DNA repair and maintains genome integrity.13, 33, 55 However, on the other hand, SIRT1 protein is overexpressed in many cancer types.52 More importantly, SIRT1 inactivates p53, leading to the downregulation of p53-mediated growth arrest and apoptosis,31, 32, 33, 34 which results in an increased risk of cancer.