Macrophage-derived fibronectin suppresses antitumor immunity via tissue stiffening and immunosuppressive cell induction in cancer mouse models.

Both tumor-associated macrophage (TAM) and tumor stiffness may support immunosuppression and limit immunotherapy response, particularly in non-small cell lung cancer (NSCLC). TAMs influence extracellular matrix (ECM) remodeling, but whether they also affect tumor stiffness, or are regulated by mechanical signals in turn, remains to be investigated. Here, we use single-cell transcriptomics of primary NSCLC samples to show that TAMs are associated with an immunosuppressive niche and are also a major source of the ECM component fibronectin (FN1). Mechanistically, macrophage-specific FN1 deficiency induces pro-inflammatory macrophages in a subcutaneous tumor mouse model, reduces ECM stiffness, increases lymphocyte infiltration into tumors, strengthens antitumor immunity, and enhances immune checkpoint blockade efficacy. Within TAMs, FN1-mediated cytoskeleton assembly and autophagy induction impair macrophage glycolysis by inhibiting the RAC1-mTOR axis, thereby limiting the antitumor activity of macrophages. Collectively, these findings highlight macrophage-derived FN1 as a mechanical cue for aggravating immunosuppression and as an intervention target to supplement immunotherapy in NSCLC.