Macrophage-derived MMP14 fosters immunosuppressive tumor microenvironment by regulating soluble semaphorin 4D

High expression of semaphorin 4D (SEMA4D) in tumor cells fosters an immunosuppressive tumor microenvironment (TME), yet the underlying tumor-macrophage crosstalk remains poorly understood. Here, we investigated this regulatory axis using in vitro co-cultures and SEMA4D gain- and loss-of-function models to assess macrophage polarization and CD8⁺ T cell effector functions. To delineate the mechanism of soluble SEMA4D (sSEMA4D) generation in vivo, we utilized a macrophage-specific matrix metalloproteinase 14 conditional knockout (MMP14cKO) mouse model and conducted an in vivo recombinant sSEMA4D (rsSEMA4D) rescue experiment. We found that tumor-derived SEMA4D drove the polarization of tumor-associated macrophages (TAMs) toward the M2 phenotype and suppressed the infiltration and function of CD8 + T cells. Mechanistically, this suppression was mediated by sSEMA4D, whose generation is promoted by TAM-derived MMP14. Genetic ablation of MMP14 in TAMs significantly reduced sSEMA4D levels, reversing M2 polarization while promoting robust M1 macrophage and CD8⁺ T cell infiltration into the tumor core, ultimately driving tumor regression. Crucially, exogenous rsSEMA4D supplementation fully abrogated these antitumor benefits in MMP14cKO mice, re-establishing the immunosuppressive TME. Our study reveals a novel mechanism of immune exclusion wherein TAM-derived MMP14 promotes the release of immunosuppressive sSEMA4D. Targeting the macrophage-MMP14–SEMA4D regulatory axis represents a promising therapeutic strategy for enhancing antitumor immunity.