Engineered Bacteria for Enhanced Radiotherapy against Breast Carcinoma

Radiotherapy is widely applied for multiple malignant tumors ablation in the clinic. However, redundant doses of X-rays might destroy normal tissue in the periphery of tumor sites. Here, we developed an integrated nanosystem (Bac@BNP) composed of engineered bacteria (Bac) and Bi₂S₃ nanoparticles (BNPs) for sensitizing radiotherapy. Bac could target and colonize in tumor sites alternatively, which overexpressed cytolysin A (ClyA) protein to regulate the cell cycle from a radioresistant phase to a radiosensitive phase. Simultaneously, peptide-modified BNPs, as a radiosensitizer with a high-Z element, was released from the surface of Bac owing to the matrix metalloproteinase-2 (MMP-2) response in the tumor microenvironment. Under X-ray irradiation, BNPs could enhance the radiotherapy sensitivity by triggering the intracellular generation of reactive oxygen species (ROS), coupled with DNA damage. In this constructed nanosystem, the combination of Bac@BNP and X-ray irradiation led to significant suppression of breast carcinoma in murine models with reduced side effects.