A novel intravesical therapy for superficial bladder cancer in an orthotopic model: oncolytic reovirus therapy.

PURPOSE: To our knowledge this is the first report of intravesical oncolytic reovirus for therapy of superficial bladder cancer in an orthotopic bladder tumor model. Superficial bladder carcinomas are often multifocal and have high recurrences after surgical resection. In 20% of cases intravesical immunotherapy fails to prevent recurrence and complications from bacillus Calmette-Guerin (BCG) are common. Human reovirus is an oncolytic virus that selectively destroys cancer cells with an activated Ras pathway. We examined the ability of this virus to kill bladder cancer cells in vitro and inhibit tumor growth in vivo. MATERIALS AND METHODS: Following cytotoxicity assays in vitro dose escalation of intravesical reovirus was tested for tumor control and toxicity in a rat model. Treatments were done twice weekly for 3 weeks. In parallel intravesical BCG was studied. Animals were monitored on a daily basis for health status and by routine urine cytology. Animals underwent necropsy at study end point and appropriate tissues were taken for histology. RESULTS: Side effects in reovirus groups were minor compared with BCG complications. Tumor response (animal survival) was 90% 100 days after tumor implantation in reovirus treated animals, whereas the highest survival in BCG treated groups was 50%. Animals treated with reovirus had significantly higher tumor-free survival than those treated with immunotherapy or normal saline (log rank test p = 0.0002 and 0.04, respectively). CONCLUSIONS: Intravesical reovirus is safe and effective in this animal model and it may have clinical applications for bladder cancer treatment.

Selective reovirus killing of bladder cancer in a co-culture spheroid model.

Up to 50% of the transitional cell carcinomas (TCC) express an activated EGF pathway involving MAP/MEK and RAF kinase thus providing a novel means to selectively eliminate transformed cells expressing such proteins. This EGF pathway expression phenotype was also confirmed in our MGH-U3 and room temperature-112 human TCC cell lines, which makes them a suitable model target for the reovirus oncolysis. We report here on an in vitro assay of co-culture spheroids using either human or rat TCC cells with their corresponding fibroblasts to examine the potential of viral selective lysis for TCC. Reovirus, a respiratory enteric orphan virus, which mammals are exposed to early in life, was used in this study. Selective killing of transformed versus normal cells was assayed by time-lapse photography, vital dye staining, immunohistochemistry, and MTT assay. In this in vitro bladder cancer model, reovirus selectively destroyed the transformed cells by lysis or induction of apoptosis. Based on these findings we have initiated an in vivo pre-clinical study on intravesical administration of reovirus in an animal model to further explore the effect of reovirus-mediated oncolysis of TCC.