Mechanical stress-induced STAT3/YAP signaling in fibroblasts programs immunosuppressive lymph node remodeling in lung squamous carcinoma.

Lung squamous cell carcinoma (LUSC) frequently metastasizes to lymph nodes, yet how tumor-intrinsic biomechanical cues influence nodal immune environments remains unclear. Here, we identify solid stress, generated during tumor expansion, as a key driver of pre-metastatic niche formation in tumor-draining lymph nodes (TDLNs). Using murine models with defined solid stress levels, we show that high-stress tumors induce early TDLN remodeling characterized by fibroblast activation and accumulation of immunosuppressive S100a8⁺ myeloid cells. Single-cell and spatial transcriptomics reveal that Col1a1⁺ fibroblasts upregulate STAT3 and YAP-dependent chemokines (CCL2, CSF1), establishing a fibroblast-myeloid signaling axis that supports myeloid recruitment and suppresses CD8⁺ T cell infiltration. Functional blockade of CCR2, CSF1R, STAT3, or YAP disrupts fibroblast-myeloid co-localization, restores antigen-presenting cell populations, and enhances CD8⁺ cytotoxic T cells activity, leading to reduced lymph node metastasis and improved survival. Mechanistically, chromatin accessibility and ChIP assays reveal direct binding of p-STAT3 and YAP at inflammatory enhancer elements in fibroblasts under mechanical strain. Cross-species spatial transcriptomic analysis confirms the inverse association between Col1a1⁺ fibroblast density and CD8A⁺ T cell presence in human LUSC tissues. Our findings uncover a mechano-immune circuit whereby tumor-derived solid stress activates fibroblast-STAT3/YAP signaling to remodel TDLNs into immunosuppressive, metastasis-permissive niches. Targeting this biomechanical axis offers a promising strategy to intercept early lymphatic dissemination in LUSC.