Mycobacterial strains that stimulate the immune system most efficiently as candidates for the treatment of bladder cancer

Background: Intravesical bacillus Calmette-Guérin (BCG) application is widely used in the treatment of superficial bladder carcinoma. Despite being an effective therapy, the pathogenicity and lethal side effects of BCG limits its usage. Intensive research has been carried out to find less toxic and more potent therapeutic agents for the treatment of bladder cancer. Researchers have focused on Mycobacterium phlei as an alternative. The cell wall extract of M. phlei is sufficient for antitumoral activity. Our preliminary experiments indicate that the fractions rich in cell wall proteins cause activation of tumor necrosis factor (TNF)-α and interleukin (IL)-12. This study aims to identify powerful and less harmful mycobacteria among 88 strains in terms of how they stimulate the immune system. Methods: Eighty-eight mycobacterial strains were grown in Middlebrook 7H9 medium. The bacterial cells were sonicated after heat treatment. The supernatants were incubated with the monocytic cell line THP-1, followed by measurement of TNF-α and IL-12 response. Results and Conclusion: In addition to M. phlei, the following 12 mycobacterial strains were selected as candidates for superficial bladder tumor treatment: M. agri, M. aichiense, M. aurum, M. brumae, M. chitae, M. chubuense, M. diernhoferi, M. gadium, M. murale, M. obuense, M. tokaiense and M. vaccae.