N-methyl-N-nitrosourea induced rat bladder carcinogenesis model

The N-methyl- N-nitrosourea (MNU) rat model of bladder cancer was chosen because it recapitulates human NMIBC, with carcinoma in situ (CIS), non-invasive papillary carcinoma (Ta), and high-grade invasive papillary carcinoma (T1) histologies, and progresses from dysplasia to NMIBC to MIBC (19). In addition, this model has been recently validated as a model reflective of human NMIBC, particularly with regard to its immune competency and clinical and immunologic response to intravesical immunotherapy and chemotherapy (20). In this model, the presence of NMIBC progresses from week 8 to week 15, at which point all rats have NMIBC. Fischer 344 female rats (age, 7 weeks) were anesthetized with an isoflurane vaporizer and nose cone system. After complete anesthesia and preparation of the surgical area, a 20G angiocatheter (BD) was placed into the rat’s urethra and the bladder was emptied of urine. MNU (1.5 mg/kg MNU dissolved in 0.30 mL of 0.9% saline, pH 6.0) was then instilled into the bladder under 45 minutes of continued sedation to prevent spontaneous micturition and allow absorption. To explore the potential for treatment to prevent recurrence, as previously described, we initiated treatment weekly from weeks 8 to 14. Treatment groups (n = 5 per group) included CDDP and PAA-CDDP NP dosed weekly. All formulations were delivered at a concentration of 0.7 mg/mLin 300 μL. Rats were sacrificed at week 15 for tissue analysis.