Abstract 5146: Establishment of an orthotopic bladder cancer model to evaluate continuous intravesical delivery of small molecule inhibitors in the nude rat

Bladder cancer is a disease with high unmet need, with no new treatments being registered in the last two decades. Intravesical delivery is an attractive option for organ-confined bladder cancer; indeed, non-muscle invasive disease is currently treated by intravesical administration of agents such as bacillus Calmette-Guerin (BCG) and mitomycin C, and neoadjuvant intravesical therapy has the potential to preserve the bladder and improve survival in M0 muscle invasive disease. Intravesical delivery has the potential to increase the therapeutic index compared with systemic dosing routes, particularly if the duration of exposure can be extended. In order to explore this concept, we have developed an orthotopic model of bladder cancer and a drug delivery method to administer gemcitabine into the nude rat bladder for one week. An orthotopic model of bladder cancer was established by serial passaging of MGH-U3 human bladder cancer cells into the muscle wall. Tumor take-rate and growth was monitored by ultrasound imaging. Serial ex vivo - in vivo passaging increased growth and take rate of the tumors in both orthotopic and subcutaneous locations. Orthotopic implantation of cells following two previous passages in vivo resulted in reproducible tumor growth and take rates of >90%. Immunohistochemistry analysis showed that the orthotopic tumors were stably epithelial in phenotype after three serial in vivo passages. Principal component analysis of gene expression (GE) data from RNA sequencing of the parental cell line, sequentially passaged cells growing ex vivo, and both subcutaneous and orthotopically implanted tumours after various numbers of passages revealed three clusters; two distinct but closely related clusters representing the orthotopic and subcutaneously growing tumors, and another distinct cluster representing the various cell lines. This analysis showed that in vitro/in vivo location of growth is a more important determinant of global GE than the process of serial passaging in vivo. We have used the iPRECIO programmable infusion pump system to continuously infuse gemcitabine into the bladders of rats with orthotopic bladder tumors. Infusion of 2.5 mg/day at a flow rate of 5 ul/h for 7 days resulted in urine concentrations in the range of 1- 10 mM (∼ 1000-fold greater than systemic plasma drug concentrations), a 4-fold increase of γH2AX and induction of both necrosis and apoptosis (10-fold induction of cleaved casapse 3) in the orthotopic tumors. This m