LINE-1 retrotransposition modulates metabolic stress and promotes cuproptosis resistance in lung squamous cell carcinoma by disrupting mitochondrial membrane homeostasis

Lung squamous cell carcinoma (LUSC) is one of the common pathological subtypes of non-small cell lung cancer, which poses significant treatment challenges due to poor response to conventional therapies and lack of effective biomarkers. Long Interspersed Nuclear Element-1 (LINE-1, L1) is a critical transposable element that has dramatically shaped the human genome and plays important roles in carcinogenesis and cancer progression. However, the functions of LINE-1 in LUSC still remain largely unknown. To elucidate the molecular mechanisms by which L1-ATP8B1 (a typical high-frequency pathogenic LINE-1 chimeric transcript in LUSC) regulates mitochondrial dynamics and cellular metabolism in LUSC, we employed a combination of in vitro and in vivo experimental models. We systematically analyzed the effects of L1-ATP8B1 on mitochondrial membrane components, key protein expression, and the underlying molecular mechanisms governing its regulation of protein expression. Additionally, we evaluated the therapeutic efficacy of a combinatorial pharmacological strategy using the reverse transcriptase inhibitor Nevirapine (NVR) and the glutathione synthesis inhibitor buthionine sulfoximine (BSO) in LUSC xenograft models. Our findings demonstrate that L1-ATP8B1 reduces the accumulation of cardiolipin, a mitochondria-specific membrane phospholipid, thereby enhancing oxidative phosphorylation and cellular energy generation. Notably, L1-ATP8B1 disrupts mitochondrial membrane homeostasis by suppressing the expression of prohibitin 1 (a critical mitochondrial membrane protein) through a mechanism involving cardiolipin-dependent SUMOylation and TRIM21-mediated ubiquitination. Furthermore, L1-ATP8B1 promotes cuproptosis resistance in LUSC cells by increasing intracellular glutathione levels. Importantly, the combinatorial treatment with NVR and BSO effectively mitigated the growth of LUSC xenografts in vivo. Our findings reveal that L1-ATP8B1 plays a critical role in mitochondrial dysfunction and LUSC aggressiveness, suggesting it may serve as a promising prognostic biomarker and a novel therapeutic target for improving clinical outcomes in LUSC patients.