Drug-Loaded Bacillus Calmette-Guérin Bacteria for Immuno-Chemo Combo Therapy in Bladder Cancer

Intravesical Bacillus Calmette-Guérin (BCG) is a well-established strategy for managing high-risk nonmuscle-invasive bladder cancer (NMIBC); however, over half of patients still experience disease recurrence or progression. Although the combined intravesical instillation of various chemotherapeutic drugs is implemented in clinical trials to enhance the BCG therapy, the outcome is far from satisfying due to severe irritative effects and treatment intolerance at high doses. Therefore, it is adopted the "biotin-streptavidin strategy" to doxorubicin (DOX)-encapsulated nanoparticles within live BCG bacteria (DOX@BCG) to improve treatment outcomes. Adherence of BCG to the bladder epithelium helps precisely target DOX@BCG to the local tumor cells and simultaneously increases intratumoral transport of therapeutic drugs. DOX@BCG effectively inhibits cancer progression and prolongs the survival of rats/mice with orthotopic bladder cancer owing to synergism between BCG-immunotherapy, DOX-chemotherapy, and DOX-induced immunogenic tumor cell death; furthermore, it exhibits improved tolerance and biosafety, and establishes antitumor immunity in the tumor microenvironment. Therefore, the drug-loaded live BCG bacterial delivery system holds considerable potential for clinical translation in the intravesical treatment of bladder cancer.