LAUSR

Studies with neuroblastoma have shown that the presence of aberrant DNA epigenetic modifications mediated by DNA methyltransferases correlates with poor prognosis, making these enzymes a target for therapeutics based on synthetic epigenetic modulators such as DNA methyltransferase inhibitors (DNMTi). Here, we have used a neuroblastoma cell line model to test the hypothesis that treatment with a DNMTi would enhance cell killing when used in combination with oncolytic Parainfluenza virus 5 (P/V virus), a cytoplasmic-replicating RNA virus. Pretreatment of SK-N-AS cells with the DNMTi 5-azacytidine substantially enhanced P/V virus-mediated cell death in a dose- and multiplicity of infection-dependent manner. Infection with the virus alone and the combination treatment with 5-azacytidine and P/V virus infection led to the activation of caspases-8, -9, and -3/7. Inhibition of caspases using a pan-caspase inhibitor minimally affected cell killing by P/V virus alone, but by contrast, largely reduced cell death mediated by 5-azacytidine treatment alone or in combination with P/V virus infection. 5-Azacytidine pretreatment dampened P/V virus gene expression and growth within the SK-N-AS cell population, which correlated with enhanced expression of important antiviral genes such as interferon-β and OAS2. Taken together, our data support the role of combination treatment using 5-azacytidine and an oncolytic P/V virus for neuroblastoma therapy.