Recent advances in bacillus Calmette–Guerin immunotherapy in bladder cancer

Th1 cytokine-secreting recombinant Mycobacterium bovis bacillus Calmette-Guérin and prospective use in immunotherapy of bladder cancer

Intravesical instillation of Mycobacterium bovis bacillus Calmette-Guérin (BCG) has been used for treating bladder cancer for 3 decades. However, BCG therapy is ineffective in approximately 30–40% of cases. Since evidence supports the T helper type 1 (Th1) response to be essential in BCG-induced tumor destruction, studies have focused on enhancing BCG induction of Th1 immune responses. Although BCG in combination with Th1 cytokines (e.g., interferon-α) has demonstrated improved efficacy, combination therapy requires multiple applications and a large quantity of cytokines. On the other hand, genetic manipulation of BCG to secrete Th1 cytokines continues to be pursued with considerable interest. To date, a number of recombinant BCG (rBCG) strains capable of secreting functional Th1 cytokines have been developed and demonstrated to be superior to BCG. This paper discusses current rBCG research, concerns, and future directions with an intention to inspire the development of this very promising immunotherapeutic modality for bladder cancer.

Immunotherapy for urothelial carcinoma: current status and perspectives

Intravesical instillation of bacillus Calmette Guérin (BCG) for the treatment of urothelial carcinoma (UC) of the bladder is based on the BCG-induced immune response, which eradicates and prevents bladder cancer. The results of recent studies have suggested that not only major histocompatibility complex (MHC)-nonrestricted immune cells such as natural killer cells, macrophages, neutrophils, etc., but also MHC-restricted CD8⁺ T cells play an important role and are one of the main effectors in this therapy. Better understanding of the mechanism of BCG immunotherapy supports the idea that active immunotherapy through its augmented T cell response can have great potential for the treatment of advanced UC. In this review, progress in immunotherapy for UC is discussed based on data from basic, translational and clinical studies. We also review the escape mechanism of cancer cells from the immune system, and down-regulation of MHC class I molecules.

Role of innate cytokines in mycobacterial infection

Cells of the innate immune system produce cytokines and lipid mediators that strongly influence the outcome of mycobacterial infection. In the case of Mycobacterium tuberculosis, the lung is a critical site for this interaction. Here, we review current information on the role of the major innate cytokine pathways both in controlling initial infection as well as in promoting and maintaining adaptive T-cell responses that mediate host resistance or immunopathology. Understanding this important feature of the host-pathogen interaction can provide major insights into the mechanisms of virulence and can lead to new approaches for immunological intervention in tuberculosis and other mycobacterial diseases.

Gene therapy for cancer: bacteria-mediated anti-angiogenesis therapy

Several bacterial species have inherent ability to colonize solid tumors in vivo. However, their natural anti-tumor activity can be enhanced by genetic engineering that enables these bacteria express or transfer therapeutic molecules into target cells. In this review, we summarize latest research on cancer therapy using genetically modified bacteria with particular emphasis on blocking tumor angiogenesis. Despite recent progress, only a few recent studies on bacterial tumor therapy have focused on anti-angiogenesis. Bacteria-mediated anti-angiogenesis therapy for cancer, however, is an attractive approach given that solid tumors are often characterized by increased vascularization. Here, we discuss four different approaches for using modified bacteria as anti-cancer therapeutics--bactofection, DNA vaccination, alternative gene therapy and transkingdom RNA interference--with a specific focus on angiogenesis suppression. Critical areas and future directions for this field are also outlined.