Tumor-stroma contributes to immunotherapeutic resistance in non-small cell lung cancer via SEMA3C-mediated immunosuppressive tumor microenvironment.

BACKGROUND: The tumor-stroma proportion (TSP) was a critical factor influencing clinical outcomes in non-small cell lung cancer (NSCLC). However, the underlying molecular mechanisms driving TSP-associated aggressiveness and its contribution to immune checkpoint blockade (ICB) resistance remained poorly understood. METHODS: Using H&E staining data from the TCGA-NSCLC cohort, patients were stratified into TSP-high and low groups. Transcriptomic profiling and single-cell RNA sequencing (scRNA-seq) were employed to identify the TSP signatures. Functional validation was conducted to investigate the role of SEMA3C in cancer-associated fibroblasts (CAFs) and its influence to tumor cells and T cells. RESULTS: TSP-high status independently predicted worse overall survival (OS) and correlated with ICB resistance. Transcriptomic analysis identified seven TSP-related genes enriched in stromal fibroblasts. Among these signatures, SEMA3C emerged as the key TSP biomarker associated with an immunosuppressive tumor microenvironment (TME) and ICB resistance in NSCLC. Functionally, SEMA3C knockdown in CAFs suppressed their migratory capacity and collagen production. Co-culture experiments demonstrated that compared to SEMA3C-knockdown CAFs, control CAFs significantly enhanced tumor cell migration and invasion while suppressing the activation and proliferation of CD8⁺ T cells. Strikingly, in vivo targeting of SEMA3C inhibited tumor growth. CONCLUSION: TSP served as an independent prognostic biomarker and predictor of ICB resistance in NSCLC. SEMA3C was identified as a crucial mediator within this axis, promoting tumor malignancy and fostering an immunosuppressive TME characterized by stromal remodeling and excluded anti-tumor immunity. This study established TSP as a clinically relevant stratification tool and revealed stromal-immune crosstalk.