Metabolic gatekeeper ACAD9 coordinates linoleic acid metabolism and redox homeostasis via mitochondrial complex I to drive ovarian cancer progression

Balancing high metabolic activity with redox homeostasis is crucial for cancer progression, particularly in high-grade serous ovarian cancer (HGSOC), which thrives in a lipid-rich environment abundance in free fatty acids, yet the key molecular regulators of this balance remain undefined. Through an in vivo genome-wide CRISPR/Cas9 knockout screen in an orthotopic ovarian cancer (OC) mouse model, we identify ACAD9 as a pivotal driver of OC progression, with its elevated expression correlating with poor patient prognosis. Multi-omics integration analysis and mechanism studies reveal ACAD9's dual role in maintaining OC metabolic homeostasis. ACAD9 preserves electron transport chain integrity and regulates linoleic acid (LA) metabolism to sustain energy production while mitigating oxidative stress. ACAD9 deficiency triggers mitochondrial respiratory collapse, inducing metabolic crisis marked by oxidative phosphorylation failure and reactive oxygen species (ROS) accumulation. Strikingly, under LA-enriched condition, ACAD9 loss redirects LA flux from β-oxidation toward membrane lipid biosynthesis, increasing polyunsaturated fatty acids incorporation. This membrane remodeling synergizes with ROS overload to create a “perfect storm” triggering ferroptosis. Our findings elucidate the dual metabolic guardianship of ACAD9 in OC, demonstrating its critical role in orchestrating mitochondrial respiration and lipid homeostasis to evade ferroptosis, which offer a potential target for the treatment of OC.