Mycobacterium bovis Bacillus Calmette-Guérin (BCG) (BCG)

Mycobacterium bovis Bacillus Calmette-Guérin (BCG) is a live attenuated strain of the Mycobacterium bovis bacterium, originally developed as a vaccine for tuberculosis (StatPearls, 2023). Beyond its role in infectious disease prevention, BCG is a standard-of-care intravesical immunotherapy for non-muscle invasive bladder cancer (NCI, 2024). The therapeutic effect is mediated by the induction of a robust local immune response within the bladder wall, where BCG acts as a biological response modifier to recruit and activate various immune cells, including macrophages, natural killer cells, and T-lymphocytes (WHO, 2024). These cells, along with a cascade of Th1 cytokines, work together to identify and destroy cancerous urothelial cells. Because it is a live organism, BCG therapy carries a risk of systemic infection, particularly in immunocompromised patients, and its efficacy can be compromised by concurrent antibiotic or immunosuppressive therapy (StatPearls, 2023). It remains one of the most successful examples of immunotherapy in clinical practice.

Other names

Bacillus Calmette-GuérinBCG vaccineMycobacterium bovis BCGTICE BCGConnaught BCG

BCG acts as a biological response modifier by inducing a potent local immune response; in bladder cancer, it binds to the urothelium via fibronectin, is internalized by cells, and triggers the release of Th1 cytokines (IFN-gamma, IL-2, IL-12) and recruitment of cytotoxic T cells and natural killer cells to destroy tumor cells (StatPearls, 2023; NCI, 2024).