Anti-Angiogenic Effects of the Superantigen Staphylococcal Enterotoxin B and Bacillus Calmette-Guérin Immunotherapy for Nonmuscle Invasive Bladder Cancer

Abstract

We compared and characterized the effects of intravesical bacillus Calmette-Guérin and/or staphylococcal enterotoxin B for nonmuscle invasive bladder cancer. A total of 75 female Fisher 344 rats were anesthetized. Of the rats 15 received 0.3 ml saline (control) and 60 received 1.5 mg/kg MNU (N-methyl-n-nitrosourea) intravesically every other week for 6 weeks. The rats were divided into 5 groups. The MNU and control groups received 0.3 ml saline. The bacillus Calmette-Guérin group received 10(6) cfu bacillus Calmette-Guérin. The staphylococcal enterotoxin B group received 10 μg/ml staphylococcal enterotoxin B. The bacillus Calmette-Guérin plus staphylococcal enterotoxin B group received the 2 treatments simultaneously. Each group was treated intravesically for 6 weeks. At 15 weeks all bladders were collected for histopathological and immunological evaluation, and Western blot. Papillary carcinoma (pTa) and high grade intraepithelial neoplasia (carcinoma in situ) were more common in the MNU group. Papillary hyperplasia was more common in the bacillus Calmette-Guérin and enterotoxin groups. Flat hyperplasia was more common in the bacillus Calmette-Guérin plus enterotoxin group. No significant toxicity was observed. The apoptosis and cellular proliferation indexes decreased in the bacillus Calmette-Guérin, enterotoxin and bacillus Calmette-Guérin plus enterotoxin groups compared to the MNU group. Intensified vascular endothelial growth factor, matrix metalloproteinase-9, Ki-67 and insulin-like growth factor receptor-1 immunoreactivity was verified in the MNU group, moderate in the bacillus Calmette-Guérin and enterotoxin groups, and weak in the bacillus Calmette-Guérin plus enterotoxin and control groups. In contrast, intense endostatin immunoreactivity was verified in the control and bacillus Calmette-Guérin plus enterotoxin groups. Bacillus Calmette-Guérin and staphylococcal enterotoxin B showed similar anti-angiogenic effects. Bacillus Calmette-Guérin plus enterotoxin treatment had additional activity compared to that of monotherapy. It was more effective in restoring apoptosis and balancing cellular proliferation, and it correlated with increased endostatin, and decreased vascular endothelial growth factor, matrix metalloproteinase-9, Ki-67 and insulin-like growth factor receptor-1 reactivity.