The PON1-NDUFA4 axis maintains mitochondrial respiratory fitness and drives lenvatinib tolerance in hepatocellular carcinoma.

Metabolic plasticity driven by mitochondrial oxidative phosphorylation (OXPHOS) is increasingly recognized as a key determinant of therapeutic tolerance in hepatocellular carcinoma (HCC), but the upstream regulators that preserve electron transport chain stability during treatment remain poorly defined. In this study, we identified paraoxonase-1 (PON1) as a clinically relevant regulator of mitochondrial metabolism and lenvatinib response in HCC. PON1 was markedly upregulated in HCC and independently associated with poor overall and recurrence-free survival. Functionally, PON1 promoted tumor growth and conferred robust tolerance to lenvatinib. Mechanistically, PON1 directly interacted with and stabilized NDUFA4, a key component required for complex IV assembly, thereby maintaining mitochondrial membrane potential, complex IV integrity, and OXPHOS-dependent adenosine triphosphate production while limiting reactive oxygen species accumulation. Genetic silencing of PON1 or NDUFA4 impaired mitochondrial respiration, increased oxidative stress, and restored lenvatinib sensitivity in HCC cells and xenograft models. Structure-guided virtual screening identified the Food and Drug Administration-approved CFTR corrector lumacaftor as a potent modulator of PON1 that disrupted the PON1-NDUFA4 interaction and enhanced the antitumor efficacy of lenvatinib in vivo. These findings identify the PON1-NDUFA4 axis as a previously unrecognized metabolic vulnerability that sustains mitochondrial respiratory fitness and lenvatinib resistance in HCC. Targeting mitochondrial protein-stabilizing mechanisms such as PON1-NDUFA4 may offer a broadly applicable strategy for overcoming therapy resistance in liver cancer and other aggressive malignancies. Implications: These findings establish mitochondrial protein stabilization as an actionable therapeutic vulnerability and provide a rationale for combination strategies to overcome targeted therapy resistance in HCC.