436. Oncolytic Adenoviruses Targeted to Esophageal Adenocarcinoma
Authors: Christopher J. LaRocca, Amanda Oliveira, Rafael Andrade, Julia Davydova, Masato Yamamoto
Journal: Molecular Therapy (2015)

In the United States and other Western countries, the incidence of esophageal adenocarcinoma (EAC) has increased in recent years. Given the poor overall survival of these patients, the need for novel therapeutics has never been greater. Our research group has designed conditionally replicative oncolytic adenoviruses (CRAd) which use the cyclooxygenase-2 (Cox2) promoter to control the tissue specificity of viral replication. EAC, along with many other human gastrointestinal malignancies, has a high expression of Cox2. We hypothesize that our vectors will selectively replicate within EAC cells, thereby minimizing potential deleterious effects on normal tissues. A chimeric 5/3 fiber was employed to maximize infectivity. Viral replication was under control of the Cox2 promoter. In addition, the E3 region was modified to allow for expression of either a luciferase or interferon alpha (IFN) transgene. The vectors were thoroughly tested in vitro using both crystal violet and MTS assays to assess cell viability following viral infection in multiple EAC cell lines. Furthermore, the in vitro cytocidal effect was also characterized when the Cox2-IFN vector was combined with cisplatin and radiation. Additionally, a nude mouse model was used to test the in vivo antitumor effect. Finally, the vectors were tested ex vivo using tissue samples derived from resected human EAC specimens. A Krumdiek tissue slicer was used to prepare the samples, which were then infected with virus and subsequently analyzed. Systemic IFN has demonstrated some success in the treatment of EAC, but its use is limited by systemic side effects. Our vectors provide a way of delivering IFN locally to the tumor. Here, the Cox2-IFN virus demonstrated a strong cytocidal effect at early time points in all tested cell lines. In fact, it caused significantly more cell death than an otherwise identical vector expressing luciferase (p<0.05), thereby demonstrating the profound effect of IFN expression. Additionally, there was a dose-dependent increase in cytocidal effect when the Cox2-IFN virus was combined with cisplatin and radiation. In vivo, that same tumor-specific IFN-expressing vector demonstrated a profound anti-tumor effect when compared to the groups treated with a wild type virus and a saline control. Replication dependent reporter expression (luciferase) was measured to assess the viral replication in the patient-derived tissue slices. Both the Cox2-controlled vector and the vector lacking a promoter showed strong replication in the EAC tissue slices as expected. Importantly, in the normal esophagus samples, there was significantly less replication in the Cox2-controlled group (p<0.05). Viral copy number (using the E4 primer) was also used to quantify viral replication. Here, a similar trend was observed as there was virtually no replication of the Cox2 virus within the normal tissue samples. We have demonstrated that a CRAd driven by the Cox2 promoter has a strong oncolytic effect both in vivo and in vitro. Moreover, our Cox2-controlled vector has demonstrated cancer-specific replication. We believe that our novel vector possesses both therapeutic efficacy and specificity, which makes it an ideal candidate for clinical translation.