Extracellular vesicle–enriched SPP1 programs MMP11⁺ fibroblast states to drive immune exclusion in lung adenocarcinoma

Cancer-associated fibroblasts (CAFs) play a key role in stromal remodeling, immune exclusion, and therapeutic resistance in lung adenocarcinoma (LUAD). However, CAF heterogeneity has largely been defined by static phenotypic classifications, leaving unresolved whether tumor cells actively instruct fibroblast differentiation toward pathogenic states that drive immune evasion and immunotherapy resistance. Specifically, the mechanisms by which tumor-stroma communication programs CAF functional states remain poorly understood. We performed integrative single-cell RNA sequencing analyses to create a detailed stromal atlas of LUAD and elucidate fibroblast lineage trajectories. Mechanistic drivers of CAF programming were examined using tumor–fibroblast co-culture systems, extracellular vesicle (EV) isolation and functional fractionation, and quantitative EV proteomics. Causal signaling pathways were confirmed through genetic and pharmacologic perturbations. Clinical relevance was evaluated across multiple independent patient cohorts and by multiplex immunofluorescence in LUAD specimens. Therapeutic implications were tested in immunocompetent mouse tumor and metastasis models, including combination treatments with PD-1 blockade. Single-cell analysis showed that fibroblasts in LUAD follow a continuous differentiation path toward a myofibroblast-like state marked by MMP11 expression. This MMP11⁺ CAF subset exhibited a transcriptional program associated with extracellular matrix remodeling, collagen organization, and immune exclusion, and was correlated with poor clinical outcomes. Tumor cells had varying abilities to trigger this CAF program, which was primarily mediated by tumor-derived EVs rather than soluble factors. Comparative EV proteomics identified secreted phosphoprotein 1 (SPP1) as a selectively enriched cargo in EVs with high CAF-programming activity. Mechanistically, EV-associated SPP1 mainly interacted with CD44 on fibroblasts to activate PI3K–AKT signaling, leading to sustained differentiation into the MMP11⁺ CAF phenotype. Clinically, the presence of MMP11⁺ CAFs was associated with dense matrix buildup, immune exclusion, reduced intratumoral T-cell infiltration, and poor responses to chemo-immunotherapy. Disrupting the EV–SPP1 pathway reduced MMP11⁺ CAF development, attenuated stromal structure, revived anti-tumor T-cell immunity, and increased tumor sensitivity to PD-1 blockade in vivo. These findings define MMP11⁺ CAFs as a functionally pro-tumorigenic fibroblast state selectively programmed by tumor-derived EV-associated SPP1, providing mechanistic evidence linking stromal reprogramming to immune exclusion and immunotherapy resistance.