SIRT1 and neoplasm: AMPK also regulates NAD+ biosynthesis and is activated by upstream signals such as Liver Kinase B1 (LKB1), Insulin Receptor Substrate (IRS), and sesquiterpenoids; LKB1 is deacetylated by Sirtuin 1 (SIRT1), forming a metabolic feedback loop that supports tumor progression (101).