Immunotherapy-based combination remodels the immunosuppressive microenvironment and enhances efficacy in advanced SMARCA4-deficient non-small cell lung cancer.

SMARCA4-deficient non-small cell lung cancer (SD-NSCLC) is associated with poor prognosis and lacks a standard treatment strategy. This multicenter retrospective study evaluated immunotherapy-based regimens and characterized the immune features of advanced SD-NSCLC using next-generation sequencing, flow cytometry, multiplex immunofluorescence, single-cell RNA and TCR sequencing, and a CRISPR/Cas9-mediated SMARCA4 knockout model. A total of 162 patients with advanced SD-NSCLC were enrolled from four Chinese cancer centers. Genomic analysis identified TP53, KEAP1, STK11, and KRAS as the primary co-mutated genes. Compared to single-agent chemotherapy, immunotherapy combined with chemotherapy and antiangiogenesis therapy demonstrated significantly longer median progression-free survival (mPFS) (12.10 vs. 2.77 months, p < 0.001). Furthermore, responders to this combination also exhibited elevated CD8+ T cell infiltration (p < 0.01). In vivo, the three-drug combination regimen significantly inhibited the growth of SMARCA4-knock-out mouse tumor cells in mice, increased infiltration of CD8+ T cells, and reduced the presence of regulatory T cells (Tregs) in the tumor microenvironment. In this mouse model, single-cell RNA-seq revealed a significant decrease in CTLA4+ Tregs with active intercellular communication following anti-PD-1 therapy. Ex vivo experiments demonstrated that treatment with anti-PD-1 markedly reduced the proportion of Tregs and concurrently increased the proportions of IFN-γ and TNF-α producing cells. Lastly, single-cell TCR-seq confirmed the expansion of specific TCR clones, particularly within CCR7+ and LEF1+ naive T cells. Collectively, these findings suggest that immunotherapy-based combination regimens may provide substantial clinical benefit for patients with SD-NSCLC by enhancing CD8+ T cell activity, suppressing CTLA4+ Tregs, and expanding tumor-reactive TCR clones.