Sun_2026_Cancer.Res__

Hepatocellular carcinoma (HCC) frequently develops resistance to lenvatinib, a frontline tyrosine kinase inhibitor. Resistance arises from heterogeneous mechanisms involving metabolic reprogramming and mitochondrial adaptation, implicating regulators of these processes as potential therapeutic targets. Here, we identified alpha/beta hydrolase domain containing 6 (ABHD6) as a critical driver of lenvatinib resistance by perturbing mitochondrial dynamics. Ligand-binding at the S148 catalytic site allosterically controlled a molecular switch between canonical enzymatic and non-canonical scaffolding functions of ABHD6, and the pro-resistance function was independent of catalysis but required an unoccupied catalytic site. In resistant HCC, the Warburg effect elevated lactate, leading to K245 lactylation of ABHD6. This modification triggered the mitochondrial translocation of ABHD6, where it functioned as a scaffold that competitively bound the fission regulator FIS1 and displaced DRP1. Disruption of the fission machinery stabilized hyperfused mitochondria, thereby conferring lenvatinib resistance by suppressing drug-induced apoptosis and ROS generation. Both inhibiting lactate production and enforcing occupancy of the S148 site with substrates or a specific inhibitor blocked formation of the ABHD6-FIS1 complex, reactivated mitochondrial fission, and restored lenvatinib sensitivity. This study identified a lactate-driven functional switch in ABHD6 and established that targeting this allosteric mechanism is an effective therapeutic strategy to overcome lenvatinib resistance.