TGM2 regulated by transcription factor NR3C1 drives p38 MAPK-mediated tumor progression and immune evasion in lung squamous cell carcinoma

Abstract

Background: Lung squamous cell carcinoma (LUSC) is highly malignant with limited therapeutic targets. Prior studies indicate transglutaminase 2 (TGM2) regulates the tumor microenvironment, but its mechanisms in driving LUSC progression and immune evasion remain unclear. Methods: The prognostic value of TGM2 was analyzed using the TCGA LUSC cohort. Key genes were screened via random forest algorithm. Functional validation was performed in NCI-H520 and SK-MES-1 cell lines. Proteomics, GSEA, and TIMER2.0 assessed downstream pathways and immune infiltration. Transcriptional regulatory databases predicted the upstream transcription factors of TGM2, which was then validated by chromatin immunoprecipitation (ChIP)-qPCR. Results: TGM2 was an independent prognostic factor for LUSC. High TGM2 expression correlated with reduced overall survival (OS, P = 0.00018) and disease-free survival (DFS, P = 0.00019). TGM2 promoted proliferation, migration, invasion, clonogenicity, and suppressed apoptosis in LUSC cells by activating p38 MAPK signaling. Elevated TGM2 levels were associated with an immunosuppressive microenvironment: decreased Th1 (R = -0.186, P < 0.0001) and NK cell infiltration (R = -0.116, P = 0.0092), and increased M2 macrophage (R = 0.164–0.528, P < 0.0001) and cancer-associated fibroblast infiltration (R = 0.469, P < 0.0001). NR3C1 was identified as a key transcription factor regulating TGM2. ChIP-qPCR analysis confirmed that NR3C1 binds to a specific site (921-935) within the TGM2 promoter, and their expression showed a strong positive correlation (R = 0.53, P < 0.0001). Conclusion: TGM2 drives LUSC progression via p38 MAPK activation and shapes an immunosuppressive microenvironment, which is transcriptionally regulated by NR3C1. This study supports TGM2 as a prognostic biomarker and suggests its potential as a therapeutic target, which may inform future combination immunotherapy strategies.