J. Sell1, A. Oliviera1, E. Jensen1, E. Greeno1, M. Yamamoto1, J. Davydova1 1University Of Minnesota,Department Of Surgery,Minneapolis, MN, USA
Introduction: Interferon-α (IFN) is a cytokine known to have direct and indirect antitumor effects. Previous studies have shown that IFN-based chemoradiation therapy (CRT) can improve survival after resection of pancreas cancer. However, its clinical utility to this point has been limited due to the severe toxicity related to its use. Our aim in this study is to evaluate our group’s novel oncolytic adenovirus (OAd) which allows targeting IFN treatment to cancer cells while sparing healthy tissue. We have previously shown the ability of IFN to sensitize cancer cells to chemotherapy as well as demonstrated an increased therapeutic effect of the drug in immunocompetent models. This study was conducted to analyze the combination of 5FU chemotherapy and our OAd in vitro in order to assess the interaction of treatments and determine the optimum combined treatment regimen.
Methods: Treatments were analyzed in two pancreatic cancer and one esophageal adenocarcinoma cell lines: Panc1, S2013, and OE19. Recombinant OAds expressing luciferase rather than IFN were used to isolate the combination of 5FU and the virus. Two viral models were evaluated. Our therapeutic virus (Cox2) selectively replicative in Cox2 expressing cancer cells and a nearly identical but universally replicative virus (wild type) were compared. Cells were treated with 0, 1 or 10 viral particles per cell and 0, 5, 10, or 20 uM 5FU. Three timing regimens were used: simultaneous administration, 5FU 48 hours before virus, and virus 48 hours before 5FU. Crystal Violet and MTS Assays were used to measure cell death. Viral Copy number to assess viral replication was measured using qPCR.
Results: Cell death analysis showed time dependent killing of each virus, with a 2 day delay for the Cox2 virus. 5FU and each virus produced dose dependent cell death independently. There was a nearly full additive effect seen in cell death from combining treatments only with simultaneously given 5uM 5FU and virus. 10 and 20 uM concentrations and virus produced less than fully additive cell death. There was little additive effect seen in treatments of virus 48 hours before 5FU, across all concentrations. Patterns observed were similar for both S2013 and OE19. Studies with Panc1 are in progress. Viral copy experiments are in progress. Treatments with 5FU 48 hours before virus are in progress.
Conclusion: Our Cox2 OAd shows a killing effect similar to wild type in multiple cancer cell lines. When combined with 5FU treatment the expected addition in overall cell death from the independent treatments diminishes, more so as 5FU concentration increases. This may suggest an inhibition of the virus by 5FU. The killing ability and interaction of the combination treatments appears different when the timing of treatments is varied, suggesting the possibility of a treatment regimen with optimal therapeutic effect. Further studies investigating different chemotherapeutic drugs should be conducted to examine these trends.
