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

Abstract 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.