Recombinant Mycobacterium bovis BCG for immunotherapy in nonmuscle invasive bladder cancer

In the past three decades, intravesical instillation of Mycobacterium bovis bacille Calmette-Guérin (BCG) has been used for treating bladder cancer and it still remains at the forefront of immunotherapy for cancer patients. Although BCG-based therapy is the most effective intravesical therapy for this kind of tumor and represents the only agent known to reduce progression into muscle invasive bladder cancer, BCG is ineffective in approximately 30-40 % of cases and disease recurs in up to 50 % of patients. Since that BCG is considered an effective vehicle for delivery of antigens due to its unique characteristics, the genetic manipulation of these mycobacteria has been appealing in the search for less toxic and more potent therapeutic agents for bladder cancer immunotherapy. Herein, we discuss current advances in recombinant BCG construction, research, concerns, and future directions to promote the development of this promising immunotherapeutic approach for bladder cancer.