Development of an orthotopic bladder tumor model in mice and demonstration of antitumor efficacy with an oncolytic adenovirus CG8840 for the treatment of bladder cancer

Proc Amer Assoc Cancer Res, Volume 45, 2004 5134 Replication-restricted oncolytic adenoviruses (OAV) have been developed for a number of tumor indications and many of them are under active investigation in clinical trials. We had earlier developed an OAV CG8840 for the treatment of uroplakin II-positive bladder tumor. In vitro studies demonstrated the preferential cytolytic activity of the virus and its efficacy in subcutaneous bladder tumor models in nude mice. Orthotopic animal models of bladder cancer more closely model the location and behavior of bladder tumors in human than non-orthotopic models. An orthotopic tumor model using the human bladder transitional cell carcinoma cell line SW780 was established on the luminal surface of the nude mice bladder. Initial seeding of the tumor cells involved the instillation of 1 x 106 tumor cells in a volume of 100 μl into the bladder lumen with a 25G catheter. The mouth of the urethra was closed with a purse string for 1 hr to allow time for attachment of the tumor cells to the bladder wall. Employing the Xenogen imaging system, in vivo imaging of the orthotopic tumor growth in mice was made possible through the use of a luciferase-expressing subclone SW780-Luc. The growth of the orthotopic tumors was assessed through the changes in the measured photon counts of the tumors. Growth in tumors sufficient for efficacy studies was observed within two weeks. The human origin of the tumors in the bladder was confirmed by immuno-histochemical staining with human anti-cytokeratin staining. Orthotopic tumors of SW780-Luc cells in bladder closely resembled superficial tumors in humans histologically. We had earlier demonstrated the enhancement in the infectivity of bladder epithelium with adenovirus following pretreatment with dodecyl-β-D-Maltoside (Ramesh et al., 2003). Similar pretreatment with 0.1% dodecyl-β-D-Maltoside was required for the efficient infection of the orthotopic tumors with adenovirus. Studies were undertaken to test the efficacy of the uroplakin II-positive bladder tumor-specific OAV CG8840 in reducing the tumor burden following intravesical instillation of the virus. Treatment of orthotopic SW780 bladder tumors with three doses of CG8840 (1x 1010 vp/treatment for 3 consecutive weeks) was efficacious in reducing tumor burden. A non-bladder specific OAV exhibited no antitumor activity. Immuno-histochemical examination of the bladder after 6 weeks showed complete absence of tumor cell in CG8840 treated mice. This simplified technique consistently produced a high incidence of superficial human tumor in mice. This will also be a useful model to conduct intravesical anti-tumor efficacy studies of OAV in combination with other therapeutic agents.