416. Enhanced Oncolytic Effect of Tumor Necrosis Factor Alpha Armed Engineered Oncolytic Measles Virus Therapy for Ovarian Carcinoma Cell Line

Abstract

Introduction. Tumor necrosis factor alpha (TNFa) has been recognized having anticancer properties, and proposed as a cancer treatment early in the 1980s, But its toxicity lead to limited use. Replication competent oncolytic viruses such as live attenuated measles virus (MV), targeting cancer cells selectively, have shown very promising results in both pre and clinical stages. one of its most useful aspects is their ability to produce high amounts of transgene products locally, resulting in high local tumor microenvironment versus systemic concentrations. Therefore, we developed Gene therapy approach to increase anti-tumor activity results from the combination of oncolytic activity, transgene-mediated direct cytotoxic effect such as TNFa-mediated apoptosis. Methods, we created novel oncolytic MV expressing murine TNFa by cloning TNFa gene into MV genome. the gene was amplified by PCR using primers that introduce restriction sites at either end of the coding sequence. The gene cloned into a plasmid encoding the entire measles genome. The insertion site for the TNFa gene was between H and L in the first version. In the second version, transgene was inserted upstream of N. The resulting full-length plasmids [MV-TNFa1 and MV-TNFa2] used to rescue the corresponding recombinant measles virus on 293-3-46 helper cells that was transfected with the MV plasmids. We evaluated the 2 recombinant versions of the MV expressing TNFa with 2 other viruses of MV, one having the sodium iodide symporter (NIS) between H and L, and the second has GFP upstream of N for oncolytic potential against ovarian carcinoma cell line SKOV-3. Infectivity, syncytium formation and cytotoxicity of recombinant MV-TNFs in SKOV-3 cells were evaluated by inverted microscopy and the MTT assay. Transgene expression in SKOV-3 cells after infection was assessed for TNFa functionality and concentration using cells that are genetically engineered for NF-kB Signaling Pathway and TNFa quantitative ELISA assay. Results, we were successful to generate the two versions of the virus with TNFa in different genome locations for each version. MV-TNFa2 shown to produce more TNFa than MV-TNFa1 (Figure-1a), but both viruses were producing functional TNFa by activating NF-kB Signaling Pathway (Figure-1b). Recombinant MV-TNFs viruses were efficiently infected SKOV-3 cell line, resulting in extensive syncytium formation followed by cell death. There was enhanced killing for the MV-TNFa1 infected cells comparing to all other viruses (Figure-1c). In conclusion, engineered MV-TNFs may be a potent and novel cancer gene therapy system. MV expressing TNFa elicited oncolytic effects in ovarian cancer cells, enhancing the killing effect which depend on the insert location.