Localization and expression of inducible nitric oxide synthase in patients after BCG treatment for bladder cancer

Treatment with Bacillus Calmette Guerin (BCG) bladder instillations is an established treatment modality for superficial urinary bladder cancer and carcinoma in situ (CIS), but the anti-tumor mechanisms following BCG instillations remain largely unknown. Previous data show increased nitric oxide (NO) concentrations in the urinary bladder from patients treated with BCG suggesting that NO-formation may be involved in the BCG mediated effect. In the present study we evaluated 11 patients with urinary bladder cancer who had received BCG treatment and 11 tumor free control subjects. We performed immunohistochemistry, Western blot and real-time polymerase chain reaction (PCR) on bladder biopsies to establish inducible nitric oxide synthase (iNOS) protein levels and localization as well as iNOS mRNA expression. Endogenous NO formation in the bladder was also measured. In patients with bladder cancer who had received BCG treatment iNOS-like immunoreactivity was found in the urothelial cells but also in macrophages in the submucosa. Furthermore, endogenously formed NO was significantly increased (p<0.001) in the BCG treated patients and they had a ten-fold increase in mRNA expression for iNOS compared to healthy controls (p=0.003). In conclusion iNOS was found to be localized to the urothelium and macrophages underlying it. Our study also confirms elevated levels of endogenously formed NO and increased mRNA expression and protein levels for iNOS in patients with BCG treated bladder cancer. These data further support the notion that NO may be involved in the anti-tumor mechanism that BCG exerts on bladder cancer cells.