1025. Efficiency, Specificity and Efficacy of Genetically-Modified Adenovirus Vector on Peritoneal Cancers

Abstract

Pancreatic cancer is one of the most lethal of all major malignancies. Although pancreatic cancer only accounts for 2% of all newly diagnosed cancers in the US, annually it is responsible for 5% of cancer deaths. We are developing a treatment approach for pancreatic cancer based on the oncolytic properties of the attenuated Edmonston strain of measles virus. While MV-Edm does not cause disease in humans it can infect cells through CD46 and SLAM receptors causing cell fusion forming multi-nucleated syncytia that eventually die via apoptosis. We have demonstrated this cytopathic effect in vitro on a panel of human pancreatic cancer cell lines (BxPC-3, L3.6pl, Panc-1, SU.86.86, MiaPaCa). We have further demonstrated the efficacy of this virus in vivo with a subcutaneous tumor model of the BxPC-3 cells. Mice treated with intra-tumoral MV-therapy out-lived the control group with a median survival ratio of 1.62 (p=0.0046). To further enhance the ability of the measles virus to more specifically target pancreatic cancer cells we developed a strategy for display of scFvs by fusion to the C-terminus of the viral attachment protein H. We have recently reported the identification of mutations in MV-H that ablate CD46 and SLAM binding (481A, 533A). Using this ablated platform we subcloned the HAA displaying human anti-CD38 or anti-EGFR scFv into full length MV-eGFP and successfully rescued these viruses. The MV-GFP-HAA αEGFR virus is an exceptional therapeutic agent for pancreatic cancer because of the over expression of EGFR on these tumor cells. As a specificity control, we have used a virus displaying a scFv against CD38, a myeloma antigen. The tropisms of the new viruses were compared against the parental MV-eGFP virus on a panel of receptor positive and negative cell lines to test the accuracy and efficiency of virus-cell entry and cell-to-cell fusion. These viruses were also characterized by western blot to confirm the chimeric H-protein. When these EGFR retargeted viruses are used to infect the pancreatic cancer cell line BxPC-3 we are able to show slightly greater levels of transduction to that observed with the parent virus that enters through CD46 and SLAM. These retargeted viruses will have the significant therapeutic advantage of binding and killing only tumor cells displaying the appropriate receptor.