SIRT1 and neoplasm: For instance, Mahmud et al. demonstrated that the downstream anti-proliferative activity of acetylated FOXO3, a tumor suppressor whose activity is vulnerable to posttranslational modifications, is activated upon SIRT1 gene silencing in BT474 breast cancer cells, suggesting that SIRT1 deacetylates and inhibits FOXO3 activity to promote breast cancer [48].