Efficacy of intravesical Bacillus Calmette-Guérin therapy against tumor immune escape in an orthotopic model of bladder cancer

The aim of this study was to evaluate the antitumor immune response of the Bacillus Calmette-Guérin (BCG) in an orthotopic bladder cancer model. The murine bladder cancer cell line MBT-2 was transurethrally implanted in the bladder of syngeneic female C3H/He mice. The animals were randomly divided into three treatment groups: Phosphate-buffered saline (PBS), low-dose BCG and high-dose BCG. The analyses of luciferin-stained tumor images 28 days after each treatment showed significant tumor growth inhibition in the high-dose group in comparison with that in the low-dose- or PBS-treated groups. In addition, the percentage of myeloid-derived suppressor cells in the high-dose group was significantly suppressed in comparison with that in the PBS and low-dose agent treatment groups. These findings are notable in terms of the clinical evaluations of this therapy for patients with bladder cancer. The outcomes of this study also provide important implications regarding antitumor immune responses in human cancer.