Construction of ammonia death-related lncRNA prognostic signature model and immunomodulatory effect in glioblastoma multiforme.

[BACKGROUND] Glioblastoma (GBM) is characterized by "glutamine addiction," a metabolic state that generates toxic ammonia byproducts. We explored the prognostic value of long non-coding RNAs (lncRNAs) associated with ammonia-induced cell death-a novel mechanism distinct from apoptosis and ferroptosis-to identify potential biomarkers and elucidate the metabolic-immune landscape of GBM.

[METHODS] Ammonia death-associated genes were identified via co-expression analysis in TCGA-GBM datasets. A prognostic signature was constructed using LASSO-Cox regression and validated in independent CGGA cohorts. Single-cell RNA sequencing (scRNA-seq) was utilized to characterize cellular heterogeneity and map ammonia death scores to specific cell populations. The expression of signature lncRNAs was validated in vitro using human GBM cell lines (U-251, U-87 MG) and normal human astrocytes via RT-qPCR.

[RESULTS] A robust three-lncRNA signature (LINC00645, AC011451.4, AC093627.22) was established. The high-risk score served as an independent predictor of significantly poorer overall survival (P < 0.001). scRNA-seq revealed that regulatory T cells (Tregs) and macrophages exhibited the highest ammonia death scores. Consistently, high-risk tumors displayed a profoundly immunosuppressive microenvironment, characterized by increased infiltration of M2 macrophages and Tregs, elevated ESTIMATE scores, and upregulation of immune checkpoints (e.g., PD-L1, IDO1). RT-qPCR results confirmed the dysregulated expression of these lncRNAs in GBM cells consistent with bioinformatic predictions.

[CONCLUSIONS] This novel signature effectively links metabolic ammonia stress to immune evasion in GBM. It serves as a reliable prognostic tool and suggests that targeting the ammonia death-related metabolic-immune axis could offer new avenues for personalizing immunotherapy.