Preferential gene transfer to BBN-induced rat bladder tumor by simple instillation of adenoviral vector

We examined the efficacy and safety of intravesical instillation of adenoviral vectors to develop gene therapy protocols for bladder cancer. In this study, an adenoviral vector containing the beta-galactosidase gene was instilled into the rat bladder with N-butyl-N-(4-hydroxybutyl) nitrosamine-induced tumors. We evaluated the effect of the glycosaminoglycan (GAG) layer on adenoviral transduction of bladder urothelium. In addition, we determined the systemic distribution of the adenoviral vector after instillation.

An adenoviral vector containing either the beta-galactosidase or the herpes simplex virus thymidine kinase gene was transurethrally instilled into the bladder, after which efficacy of gene transfer was evaluated by staining with 5-bromo-4-chloro-3-indolyl-beta-D-galactopyraminoside, and the distribution of the gene was examined by reverse transcriptase-polymerase chain reaction. To determine the extent to which the GAG layer may have inhibited gene transfer by the adenoviral vector, prior to instillation of adenoviral vector, normal bladders were pretreated with either phosphate-buffered saline or HCl, which would destroy the mucosal GAG layer.

We found that intravesical instillation of an adenoviral vector caused preferential gene transfer to the tumor cells and that expression of the transferred gene occurred exclusively in the bladder. Removing the GAG layer rendered the normal bladder highly susceptible to adenoviral gene transfer, indicating that GAG on normal mucosa prevented adenoviral gene transfer.

BBN-induced bladder tumors were preferentially transduced by instillation of adenoviral vectors probably due to the lack of GAG layers on their surface. Intravesical instillation of adenoviral vectors does not result in systemic infection. These results encourage the consideration of gene therapy in the treatment of human bladder cancer.