Ultrasound-Driven Lysis of Tumor-Resident Bacteria Awakens Innate Immunity for Systemic Cancer Therapy

Abstract Tumor-resident bacteria establish a profound immunosuppressive microenvironment that compromises cancer immunotherapy. While ablating these microbes holds therapeutic promise, broad-spectrum antibiotics can cause systemic dysbiosis, and the Gram-negative outer membrane can restrict the entry of conventional sonosensitizers, limiting the antibacterial efficacy of sonodynamic therapy (SDT). Here, we report an ultrasound-driven, bacteria-targeted immunotherapy utilizing polyarginine-functionalized peptide-sonosensitizer conjugates to achieve the in situ pulverization of the tumor Fusobacterium nucleatum (F. nucleatum), thereby eliciting potent innate antitumor immunity. The cationic conjugates electrostatically intercalate into Gram-negative bacterial membranes, inflicting a structural predisruption. Subsequent ultrasound irradiation synergizes localized sonochemical oxidation with mechanical shear forces to thoroughly shatter the bacteria. This targeted microbial fragmentation liberates massive quantities of pathogen-associated molecular patterns (PAMPs) that, unlike tumor-derived signals from conventional SDT, decisively reprogram macrophages toward an antitumor M1 phenotype to awaken innate immunity. Synchronized with tumor-specific antigens released via conjugate-induced immunogenic cell death, the liberated PAMPs synergistically amplify antigen presentation and optimally drive dendritic cell maturation. In a bacteria-colonized murine colorectal cancer model, this localized therapy markedly suppressed primary tumor growth and elicited both a pronounced abscopal effect against distant tumors and antitumor immune memory. By repurposing complicit bacteria into potent endogenous adjuvants, this ultrasound-driven strategy reverses bacteria-mediated immunosuppression, offering a transformative paradigm for treating microbiome-colonized solid tumors.