639. Oncolytic Adenovirus Expressing IFN Alpha Works Synergistically with Chemoradiation
Authors: Amanda O. Salzwedel, Christopher LaRocca, Joohee Han, Julia Davydova, Masato Yamamoto
Journal: Molecular Therapy (2016)

Aside from curative resection, there is no curative treatment against pancreatic adenocarcinoma (PDAC) at present. Late diagnosis and high recurrence results in five-year survival of 6%. Notably, Phase II trials based on adjuvant therapy combining systemic IFN Alpha (IFN) and chemoradiation reported 30-50% increase in two-year survival and impressive 35% increase in five-year survival of PDAC patients. Despite promising results, trial drawbacks included high patient dropout due to IFN systemic toxicity and low IFN levels in tumors. Low intratumoral IFN hampered the full potential of the therapy while IFN is known to induce tumor apoptosis, chemoradio sensitization, and decreased tumor neo-vasculatization. Aiming to improve efficacy and tolerability of IFN therapy, we have developed an oncolytic adenovirus expressing human IFN (OAd-IFN). Vector has Ad5/3 fiber modification and overexpresses Adenoviral Death Protein respectively contributing to increased infectivity and oncolysis. Taking advantage of Cox-2 up-regulation in PDAC, the Cox-2 promoter was included in the upstream of Adenovirus E1 region, restricting vector replication to cancer cells. Human IFN-alpha gene was placed in the Adenovirus E3 region in the way that its expression is controlled by the adenovirus major late promoter. Therefore, IFN expression in this vector is replication dependent. To test the vector in an immunocompetent syngeneic hamster model of pancreatic cancer, OAd-IFN expressing hamster IFN was generated. Vector contains RGD fiber modification enhancing its infectivity in hamster cells. MTS and crystal violet assays demonstrated sensitization of PDAC cells to chemotherapy (5-FU, Cisplatin, and Gemcitabine), and radiation (4 and 8Gy) by OAd-IFN. Comparison between OAd-IFN and control vector not expressing IFN (OAd-LUC) indicated that IFN expressed by OAd-IFN is functional in combination therapy sensitizing PDAC cells to chemoradiation. Colony formation assay showed that combinations of OAd-IFN with chemotherapy, radiation, or chemoradiation are synergistic and exhibit superior killing effect compared to groups without OAd-IFN. In vivo studies using immunocompetent syngeneic hamster model of pancreatic cancer showed that combinations including OAd-IFN resulted in augmented tumor shrinkage and survival compared to groups treated with chemotherapy, radiation, chemoradiation, or OAd-LUC + radiation. Hexon staining and viral DNA quantification by qPCR show OAd-IFN effectively replicates and spreads in tumors. Our data suggests OAd-IFN synergistically improves chemoradioation in PDAC cells, and shows superior therapeutic effect when treating immunocompetent model of pancreatic cancer. Vector capacity to express high levels of IFN intratumorally and the strong synergism between OAd-IFN and radiation, chemotherapy, and chemoradiation indicates OAd-IFN will contribute to more olerable and effective IFN therapy. Strong synergism between OAd-IFN and chemoradiation combined with focal expression of IFN can help to reduce not only IFN toxicity, but also dose-dependent toxicity of chemoradiation. Considering systemic IFN injection combined with chemoradiation is one of the few therapies to effectively treat pancreatic cancer, usage of OAd-IFN in combination with chemoradiation has great potential to result in more effective and tolerable therapy agaisnt pancreatic cancer.