SUMOylation Protects FASN Against Proteasomal Degradation in Breast Cancer Cells Treated with Grape Leaf Extract

Existing therapeutic strategies for breast cancer are limited by tumor recurrence anddrug-resistance. Antioxidant plant-derived compounds such as flavonoids reduce adverse outcomesand have been identified as a potential source of antineoplastic agent with less undesirable sideeects. Here, we describe the novel regulation of fatty-acid synthase (FASN), the key enzyme in denovo fatty-acid synthesis, whereby Vitis vinifera L. cv Vermentino leaf hydroalcoholic extract lowersits protein stability that is regulated by small ubiquitin-like modifier (SUMO)ylation. The phenoliccompounds characterization was performed by liquid chromatography-mass spectrometry (LC-MS),whereas mass spectrometry (LC-MS/MS), Western blotting/co-immunoprecipitation (Co-IP) andRT-PCR, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), clonogenicity assays,and FACS analysis were used to measure the expression of targets and tumorigenicity.Vermentino extract exhibits antitumorigenic eects, and we went on to determine that FASNand ubiquitin-conjugating enzyme 9 (UBC9), the sole E2 enzyme required for SUMOylation,were significantly reduced. Moreover, FASN was found SUMOylated in human breast cancertissues and cell lines, and lack of SUMOylation caused by SUMO2 silencing reduced FASN proteinstability. These results suggest that SUMOylation protects FASN against proteasomal degradationand may exert oncogenic activity through alteration of lipid metabolism, whereas Vermentinoextract inhibits these eects which supports the additional validation of the therapeutic value of thiscompound in breast cancer.