Characterization of a novel transplantable orthotopic murine xenograft model of a human bladder transitional cell tumor (BIU-87)

For the evaluation of anti-human bladder cancer immunotoxin approaches, the orthotopic nude murine model that mimics the human counterpart is essential for preclinical evaluation of new treatment modalities. The objective of this study was to develop and characterize such a model. To accomplish this, the established human bladder transitional cell carcinoma (TCC) cell line, BIU-87, was transplanted orthotopically into immunodeficient nude mice. BIU-87 TCC cells were grown in monolayer cell culture and instilled intravesically as single cell suspensions into bladders that had been conditioned with mild acid washing. Tumor growth was assessed weekly by subjecting the mice to magnetic resonance imaging (MRI). At intervals following implantation and MRI tumor detection, the animals were sacrificed for necropsy, histological examination and immunocytochemical studies. The overall tumor establishment was 93% (52/56 mice) at 7-36 days, while in a subgroup of animals sacrificed at 12-13 days, 40 out of 42 animals (95%) developed TCC, the majority of which was superficial. Tumor stage was assessed by gross pathology and light microscopy. Histological examination of the tumor specimens confirmed the presence of grade II-III TCC. Immunocytochemistry confirmed that the tumor model maintained the features of BIU-87 cells. The changes seen on MRI correlated well with the extent of tumor invasion identified histologically. Carcinoma in situ could be detected histologically 7-9 days post-inoculation, and progressed to papillary tumor or invasive disease thereafter. The orthotopic BIU-87 TCC model is highly reproducible and is ideal for preclinical studies on experimental intravesical therapies.