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

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.