SIRT1 and neoplasm: Ubiquitination (via SCF-FBXW7, RNF20, RNF139) or deacetylation (via SIRT1) promotes SREBP1 degradation, inhibiting fatty acid metabolism and maintaining lipid homeostasis. mTORC1 activation and SREBP1 acetylation enhance its stability and promote lipid metabolism, supporting tumor growth.