An Engineered Probiotic Consortium Based on Quorum-Sensing for Colorectal Cancer Immunotherapy

Recent progress in synthetic biology has empowered engineered probiotics to sense tumor-specific physicochemical signals, thereby facilitating targeted in situ drug delivery. Here, an engineered probiotic consortium capable of integrating multiple tumor microenvironment (TME) signals and orchestrating multi-therapeutic payloads release through an orthogonal quorum-sensing system is designed. The probiotic consortium can respond to three characteristic TME parameters, pH, hypoxia, and high-lactate levels, in order to achieve controlled release of lactate depletion enzyme (LdhA) for metabolic environment improvement and the programmed death ligand 1 (PD-L1) nanobody for immune checkpoint inhibition. Using the humanized PD-1 mouse model bearing hPD-L1 MC38 tumor and the humanized peripheral blood mononuclear cells (PBMC) mouse model bearing HT-29 tumor, it is demonstrated that this self-regulating microbial consortium achieves sustained oscillations and significantly suppresses tumor progression. Mechanistic studies reveal that the antitumor efficacy activates CD8⁺, CD4⁺, and IFN-γ⁺ T cells, coupled with diminished immunosuppressive Foxp3⁺ regulatory T cell infiltration. This work advances the development of engineered live biotherapeutic products for cancer therapy and provides a modular platform for microbial consortium-based precision medicine.