AAV-mediated delivery of interferon-β for the treatment of retinoblastoma in preclinical models

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3565 Background: Interferon-β has anti-tumor properties against a variety of malignancies through direct cytotoxicity as well as immunological effects. In order to circumvent limitations of IFN-β therapy, we have developed an adeno-associated viral gene therapy approach to deliver IFN-β directly to tumors. In this study, we tested the efficacy of AAV mediated delivery of IFN-β in preclinical retinoblastoma models. Retinoblastoma is an ideal candidate for gene-therapy based anti-cancer treatments because viral infection and IFN-β delivery can be contained within the ocular environment thereby minimizing systemic toxicity. Methods: Retinoblastoma cell lines Weri and Y79 were treated in vitro with recombinant human Interferon-β and then subjected to Viacount assays, Nexin apoptosis assays, FACS cell cycle analysis, and immunolabeling for proliferation (BrdU) and apoptosis (caspase and TUNEL). An orthotopic Xenograft retinoblastoma rat model with luciferase reporter were established and treated with single subconjunctival injection of AAV-IFN-β gene therapy. Xenogen in vivo imaging was used to follow tumor volume. Blood and tissue samples (ELISA) were obtained to determine IFN-β levels. Results: Weri and Y79 cells showed maximum reduction in viability at 500 IU/ml and 2500 IU/ml respectively. Weri response was found to be cell death by Caspase and TUNEL assay. Y79 response was found to be due to suppression of proliferation as measured by BrdU incorporation and cell cycle analysis. In the retinoblastoma xenograft model there was no increase in tumor volume by serial in vivo imaging compared to control animals. Stable levels of IFN-β were maintained at 20 ng/ml >6weeks following injection. Plasma levels were undetectable 42 days following treatment. Conclusions: Retinoblastoma cell lines exhibit pleiotropic responses to IFN-β consistent with previous studies. Intravitreal injection of AAV-IFN-β resulted in efficient retinal infection and sustained IFN-β production. Viral spread outside of the eye was not detected. Using our retinoblastoma xenograft model we found that intravitreal injection of AAV-IFN-β had a potent anti-tumor effect in vivo. These data suggest that AAV mediated delivery of IFN-β may provide a complementary approach to systemic chemotherapy. No significant financial relationships to disclose.