Astragalus polysaccharide-based thermoresponsive hydrogel loaded with β-elemene nanoemulsion in combination with anti-PD-L1 therapy for triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is classified as an immunologically cold tumor, which markedly weakens the therapeutic efficacy of immune checkpoint blockade (ICB) represented by anti-PD-L1 therapy. To overcome this limitation, an astragalus polysaccharide (APS)-based thermoresponsive hydrogel loaded with a β-elemene (ELE) nanoemulsion (ELE-NE-gel) was developed in this study with the aim of enhancing ICB efficacy by inducing immunogenic cell death (ICD) and remodeling the tumor immune microenvironment. In vitro assays proved that ELE-NE-gel efficiently eliminated 4 T1 cells and successfully triggered immunogenic cell death (ICD). As the hydrogel scaffold, APS also exhibited prominent intrinsic immunomodulatory capacity. In the murine TNBC model, combined ELE-NE-gel and anti-PD-L1 treatment exerted superior antitumor effects compared with monotherapy. This enhanced therapeutic effect resulted from the complementary functions of the hydrogel components: ELE induced ICD, whereas APS reprogrammed tumor-associated macrophages (TAMs) from immunosuppressive M2 phenotype to the antitumor M1 phenotype. Together, these effects promoted dendritic cell maturation and enhanced the activation of tumor-infiltrating T lymphocytes. Furthermore, machine learning analysis of clinical transcriptomic data identified the PI3K/AKT-signaling pathway as a potential therapeutic target in TNBC. This finding was experimentally validated by q-PCR and Western blotting. Collectively, our findings establish ELE-NE-gel as both an effective ICD inducer and an immunomodulatory platform that acts synergistically with anti-PD-L1 therapy. This combinatorial strategy, preliminarily validated in vivo, suppressed TNBC progression through downregulation of the PI3K/AKT-signaling pathway as an important immunotherapeutic approach for TNBC.