435. Effects of Chemotherapy and Radiation on Replication of Interferon-Expressing Adenovirus in Pancreatic Cancer Cells

Abstract

Pancreatic Cancer is a disease for which there are very limited efficacious treatments, resulting in a 5-year survival rate for affected patients around only 6%. Our group has developed a recombinant oncolytic adenovirus (OAd-IFN) aimed for use as an additional treatment for this disease. Manipulations in the viral genome include enhanced oncolysis with an overexpression of the adenoviral death protein, enhanced infectivity with a genetically modified fiber that has replaced the serotype 3 Ad fiber with that of a serotype 5 Ad, conditional replication targeted to pancreatic cancer cells by linking replication with the Cox-2 promoter, and an expression of the gene for human interferon α within the E3 region to enhance the therapeutic effects of chemotherapy and radiation through the antitumor effects of the cytokine.Our previous work analyzing the therapeutic abilities of IFN expressing vectors in human pancreatic cancer xenografts in immonudeficient nude mice and in syngeneic hamster pancreatic cancer nodules in immunocompetent Syrian hamsters, showed a more evident antitumor effect of OAd-IFN in the latter models. This suggests the success of OAd-IFN as an immune system stimulator, making it a promising candidate for combination therapy approaches. In vitro studies in hamster pancreatic cancer cell lines showed significantly improved killing effects when OAd-IFN was added to conventional chemotherapy and radiation treatments, as well as greater killing ability with triple therapies using OAd-IFN versus an OAd without IFN. Moreover, killing effects became more pronounced over time, showing that the oncolytic impact of the IFN depends on replication of the virus to express the IFN gene.The goal of this study is to investigate the effects of chemotherapy and radiation on the replication of our OAd-IFN, since understanding these interactions is necessary to evaluate the possibility of using this virus as part of a combined therapeutic regimen. Specifically, the adenoviral replicative ability was measured within pancreatic cancer Mia-Paca 2 cells under various conditions of 5FU and radiation exposure. Replication was analyzed by quantifying viral DNA extracted from treated cells at two time points post infection. In preliminary trials, cells were infected with the virus either two days prior to receiving 5FU and radiation or one day post 5FU treatment. Based on the initial data collected, radiation seemed to have no effect on viral replication. 5FU treatment prior to viral infection resulted in an increase in replication at low dose, and a decrease in replication at high dose, however, this effect was only seen at the first time point. Similarly, 5FU treatment post infection showed minor inhibition of viral replication at high doses, with little to no effect observed in the low dose. Further trials including a simultaneous treatment with 5FU and virus are being done to better explore these observed effects, and future trials will be conducted exploring for similar patterns using Gemcitabine and Cisplatin in place of 5FU.