LAB-EXPERIMENTAL (PRE-CLINICAL) THERAPEUTICS AND PHARMACOLOGY

Abstract

BACKGROUND: Glioblastoma multiforme (GBM) is a grade IV malignant astrocytoma with a median patient survival of 15 months. Oncolytic virus (OV) therapy uses engineered viruses to selectively destroy cancer cells. Rapid antiangiogenesis mediated by oncolytic virus (RAMBO) is an OV that expresses the anti-angiogenic transgene Vstat120. Mice bearing intracranial tumors treated with RAMBO survived significantly longer than mice treated with a control virus. In addition to its anti-angiogenic effects, RAMBO also replicated better than a control virus in vivo. These results suggested that the expression of Vstat120 may also temper the innate immune response to viral infection. This project investigates the effect of RAMBO on host innate cellular defense responses mediated by monocytes/microglia. METHODS: Co-culture experiments were established with murine microglia and glioma cells infected with RAMBO virus or a control virus. The expression levels of various cytokines were analyzed via quantitative PCR. In other experiments, mice bearing intracranial tumors were treated with RAMBO or a control virus. The brains of these treated mice were harvested, and flow cytometric analysis was conducted to examine microglia/macrophage infiltration and activation in the brain. RESULTS: Results of co-culture experiments showed a significant downregulation of type-1/2 interferons and inflammatory cytokines and chemokines in microglia co-cultured with RAMBO-infected glioma cells compared to a control virus. Flow cytometric analysis of microglia/macrophages revealed a significant reduction in the number of these cells in the brains of mice treated with RAMBO compared to control virus. There was also a significant reduction in the activation of microglia in brains of mice treated with RAMBO. CONCLUSIONS: The expression of Vstat120 within the RAMBO virus mediates an antiinflammatory effect that tempers the innate immune response upon infection and allows the virus to propagate and destroy tumor cells more effectively than traditional OVs. This study further validates the use of the RAMBO virus as a therapeutic for treating GBMs.