ANXA1 Promotes Endoplasmic Reticulum–Mitochondria Calcium Coupling to Sustain Lenvatinib Resistance in Hepatocellular Carcinoma

Abstract Lenvatinib is the most widely used first-line treatment for advanced hepatocellular carcinoma (HCC). Nevertheless, drug resistance remains a major clinical challenge, highlighting the need to identify the underlying mechanistic drivers. Here, we identified a role for annexin A1 (ANXA1) in promoting lenvatinib resistance by supporting endoplasmic reticulum (ER)–mitochondria communication. Live-cell structured illumination microscopy revealed that ANXA1 deficiency induced the dissociation of ER–mitochondria contact sites (ERMCS), and Ca2+ kinetic analysis revealed that ANXA1 enhanced mitochondrial Ca2+ coupling. ANXA1 promoted ERMCS by directly binding the ER–mitochondria Ca2+ transfer tethers GRP75 and ITPR1 and promoting their interaction. Functionally, ANXA1 sustained oxidative phosphorylation following lenvatinib treatment and promoted cell survival. We further found that ANXA1 RNA stability was governed by an 8-oxoguanine modification–mediated ROS feedback loop. Therapeutically, photoacoustic imaging–guided in vivo analyses demonstrated that targeting this epigenetic–organelle communication feedback loop resensitized HCC to lenvatinib treatment, inhibiting peritumoral angiogenesis and improving the intratumoral hypoxic microenvironment. These findings uncover ERMCS formation as a driver of lenvatinib resistance in HCC, establishing a potential therapeutic strategy for targeting organelle communication to reverse drug resistance.