LINE-1 retrotransposition drives lipid metabolic reprogramming and immune suppression in lung squamous cell carcinoma via cPLA2/5-LOX axis

Background : Long interspersed nuclear element-1 (LINE-1; L1) retrotransposition is frequent in lung squamous cell carcinoma (LUSC), yet its functional impact remains largely unelucidated. We previously identified recurrent L1-ATP8B1 (L1 insertion in ATP8B1) associated with poor prognosis. Given ATP8B1's role in lipid homeostasis, we hypothesize L1-ATP8B1 drives lipid metabolic reprogramming to promote LUSC progression. Methods : We integrated transcriptomic analyses of The Cancer Genome Atlas (TCGA) and validation cohorts with targeted metabolomics, functional assays, and tumor-immune cell co-culture systems. Mechanistic studies were conducted via genetic perturbation, pharmacologic inhibition, and rescue experiments in both in vitro and in vivo models. Results : Gene Ontology and KEGG enrichment analysis revealed L1-ATP8B1 correlated with deregulated lipid metabolism, particularly arachidonic acid (AA) metabolism. Metabolomic profiling results confirmed elevated AA-derived 5-HETE and 5-oxo-ETE (the oxidation metabolite of 5-HETE) in L1-ATP8B1-over-expressing cells. Mechanistically, L1-ATP8B1 up-regulated the transcriptional levels of PLA2G4 and ALOX5 to enhance AA release and 5-HETE generation. Pharmacologic inhibition of the activity of their metabolic enzymes cytosolic phospholipase A₂ (cPLA₂) and 5-lipoxygenase (5-LOX) abrogated tumor progression, whereas exogenous 5-oxo-ETE rescued the effects. Further, we found L1-ATP8B1 induced immune suppression by recruiting myeloid-derived suppressor cells (MDSCs). Co-culture experiments demonstrated 5-oxo-ETE enhanced the immunosuppressive function of MDSCs by activating non-canonical NF-κB signaling, thereby inhibiting T cell proliferation and IFN-gamma production-an effect reversed by 5-LOX inhibition. Conclusions : Our findings uncover a previously unrecognized L1/cPLA2/5-LOX/NF-κB axis linking lipid metabolic reprogramming to LUSC immune evasion. L1-ATP8B1 drives tumor aggressiveness and immune suppression via lipid mediators. Targeting this pathway is a promising therapeutic strategy to overcome immune resistance in LUSC.