Peptide hydrogels loaded with irradiated tumor cell secretions enhance cancer immunotherapy

In advanced stage patients, traditional cancer chemotherapies often demonstrate limited tumor growth inhibition and fail to elicit sufficient anti-tumor immunity required for long-lasting responses. Herein, we developed a therapeutic peptide hydrogel manufactured using a PEG cross-linked melittin-peptide scaffold that not only itself induces tumor cell killing, but also encapsulates the processed cell secretions of autologous, irradiated tumor cells. MLT-RADA-Polyethylene glycol (MRP) loaded with the concentrated ultrafiltration (UF) retentate from irradiated tumor cell media, denoted as UF@MRP effectively reshapes the tumor microenvironment (TME) by stimulating dendritic cell maturation and reprogramming macrophages toward a tumoricidal M1 phenotype. In multiple murine tumor models, in which immune checkpoint blockade (ICB) alone did not control advanced disease, intratumoral administration of UF@MRP enhanced ICB efficacy, leading to prolonged survival. The combination of UF@MRP and ICB appears to be an effective approach to rapidly kill tumor cells, diminish immunosuppression in the TME, and activate host adaptive immune responses, all of which work in concert in an immunotherapy regime to control established and aggressive tumors.