P08.60 RAMBO (rapid anti angiogenesis mediated by oncolytic virus) decreased bevacizumab-induced glioma cell invasion

INTRODUCTION: Anti-VEGF therapies such as bevacizumab have been shown to attenuate VEGF-mediated angiogenesis, to decrease vascular permeability, and to inhibit tumor growth in malignant glioma. Conversely, bevacizumab has also been reported to induce invasive proliferation. Oncolytic viral therapy is considered to be a promising treatment modality for malignant glioma. Previous studies indicate that RAMBO (rapid anti angiogenesis mediated by oncolytic virus), a vasculostatin-expressing Herpes simplex virus (HSV)-1-derived oncolytic virus, has potent anti tumor activity against malignant glioma. In this study, the effects of RAMBO on bevacizumab-induced invasive changes in glioma were evaluated. MATERIALS AND METHODS: RAMBO is composed of the cDNA encoding for human vasculostatin (Vstat120), driven by the HSV-1 IE4/5 promotor, within the backbone of an attenuated HSV-1 virus (HSVQ). Experiments were conducted using the human malignant glioma cell lines U373 and U87deltaEGFR, and Vstat120 expression in the supernatant was assessed by western blotting. The effect of the combination of RAMBO with bevacizumab was assessed by cytotoxicity assays, scratch wound assays, and Matrigel invasion assays. RESULTS: Vasculostatin was detected in cell lysates and secreted CM at 14 hours after infection with RAMBO. The cytotoxicity assay demonstrated that bevacizumab did not increase the cytotoxicity of RAMBO against glioma cells. Conversely, in the scratch wound assay, RAMBO CM significantly reduced both the number of migrating cells and the rate of migration compared with saline used as control. Furthermore, the number and the rate of migrating cells induced by bevacizumab treatment was reduced by RAMBO CM. In the Matrigel invasion assays, the number of invasive cells induced by bevacizumab was reduced by RAMBO CM. CONCLUSIONS: These results demonstrated that RAMBO suppressed bevacizumab-induced glioma invasion, which may lead to a promising approach for the treatment of malignant glioma.