The mechanism of action of BCG therapy for bladder cancer—a current perspective

Despite nearly four decades of clinical experience with Bacillus Calmette–Guérin (BCG) for bladder cancer, the mechanism of its therapeutic effect is still under investigationThe requirements for effective BCG therapy include an intact immune system, live BCG, and close contact of BCG with bladder cancer cellsImportant constituents of the cellular inflammatory response to BCG include CD4+ and CD8+ lymphocytes, natural killer cells, and granulocytesImportant elements of the humoral immune response to BCG include TRAIL (tumour necrosis factor-related apoptosis-inducing ligand), IL-2, IL-8, IL-18, IL-12, interferon (IFN)-γ, and tumour necrosis factor (TNF)Bladder cancer cells and benign urothelial cells might have a role in the initial recognition and processing of BCG, leading to immune system recruitmentFuture investigation will hopefully lead to the discovery of clinically useful predictors of response to BCG and development of recombinant BCG strains with improved efficacy and decreased toxicity