Implantable Synthetic Immune Niche for Spatiotemporal Modulation of Tumor‐Derived Immunosuppression and Systemic Antitumor Immunity: Postoperative Immunotherapy

Abstract The development of biomaterial‐based immune niches that can modulate immunosuppressive factors in tumor microenvironment (TME) will be a key technology for improving current cancer immunotherapy. Here, implantable, engineered 3D porous scaffolds are designed to generate synergistic action between myeloid‐derived suppressor cell (MDSC)‐depleting agents, which can accommodate the establishment of a permissive immunogenic microenvironment to counteract tumor‐induced immunosuppression, and cancer vaccines consisting of whole tumor lysates and nanogel‐based adjuvants, which can generate tumor antigen‐specific T cell responses. The local peritumoral implantation of the synthetic immune niche (termed immuneCare‐DISC, iCD) as a postsurgical treatment in an advanced‐stage primary 4T1 breast tumor model generates systemic antitumor immunity and prevents tumor recurrence at the surgical site as well as the migration of residual tumor cells into the lungs, resulting in 100% survival. These therapeutic outcomes are achieved through the inhibition of immunosuppressive MDSCs in tumors and spleens by releasing gemcitabine and recruitment/activation of dendritic cells, enhanced population of CD4⁺ and CD8⁺ T cells, and increased IFN‐γ production by cancer vaccines from the iCD. This combined spatiotemporal modulation of tumor‐derived immunosuppression and vaccine‐induced immune stimulation through the iCD is expected to provide an immune niche for prevention of postoperative tumor recurrence and metastasis.