student research day - Case Western Reserve University School of ...

Steven Healan
RAMBO, a novel oncolytic virus designed to modulate OV-induced changes in the tumor microenvironment of
malignant gliomas
Steven Healan, J. Hardcastle, E.A. Chiocca and B. Kaur
Comprehensive Cancer Center, Ohio State University Medical Center
Glioblastoma multiforme (GBM) is a fatal cancer with no current effective means of therapy. Recently,Oncolytic
virus (OV) therapy has emerged as a putative treatment option. However, OV treatment of intracranial rat tumors
triggers a host defense response resulting in increased and decreased secretion of pro- and anti-angiogenic factors
respectively, leading to significant neo-angiogenesis and regrowth in the residual disease. We have previously
shown that Brain Angiogenesis Inhibitor-1 (BAI1) expression is lost in a majority of GBMs and glioma cell lines, and
that expression of its extracellular fragment (vasculostatin) results in slower glioma growth in vivo. To counter the
pro-angiogenic change in the tumor microenvironment after OV treatment, we have engineered and tested RAMBO
(rapid anti-angiogenesis mediated by oncolytic virus), which is a novel HSV-1 based attenuated OV that expresses
vasculostatin. RAMBO treatment of mice bearing intracranial and subcutaneous gliomas revealed a significant
increase in median survival (26 vs. 56 days for intracranial tumors and 19 vs. 41 days for subcutaneous tumors)
as compared to HSVQ treatment (control). As BAI1 has been shown to be an engulfment receptor on
macrophages, we propose that vasculostatin, produced by RAMBO infected cells, binds to the apoptotic marker
phosphatidylserine (Pstdr) expressed on infected cells, and prevents recognition and clearance by phagocytes,
allowing enhanced viral propagation. To test this, we performed synchronized infections of U251 T2 GBM cells with
RAMBO and HSVQ, and visualized Pstdr expression on the cell surface at various time points using a commercially
available apoptotic marker, Annexin V. Initial results confirmed OV-induced apoptosis in infected glioma cells up to
3.5 hours post infection. We anticipate that later time points will demonstrate decreased detectable Pstdr on the
surface of cells infected with RAMBO compared to those infected with HSVQ, resulting in decreased recognition and
clearance by phagocytes and enabling necessary OV replication
Supported by NIH R21NS056203-02, and the Alex Lemonade Stand Foundation
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