Abstract
Vascularization is a common pathology for many solid tumors, and therefore anti-angiogenic strategies are being investigated as a therapeutic target for treatment. Numerous studies are also being conducted regarding the effects of oncolytic viruses, including ImlygicTM, an FDA approved oncolytic herpes simplex virus-1 (oHSV) for the treatment of highly vascularized tumors such as Kaposi sarcoma (NCT04065152), and brain tumors. To our knowledge, the effects of combining oncolytic HSV with angiogenesis inhibition on endothelial cell activation has not been previously described. Here, we tested the effects of Rapid Antiangiogenesis Mediated By Oncolytic Virus (RAMBO), an oHSV which expresses a potent anti-angiogenic gene Vasculostatin on endothelial cell activation in heavily vascularized solid tumors. oHSV treatment induces endothelial cell activation, which inhibits virus propagation and oncolysis in adjacent tumor cells in vitro. Consistently, this was also observed in intravital imaging of intracranial tumor-bearing mice in vivo where infected tumor endothelial cells could efficiently clear the virus without cell lysis. Quantitative real-time PCR (Q-PCR), leukocyte adhesion assay, and fluorescent microscopy imaging data, however, revealed that RAMBO virus significantly decreased expression of endothelial cell activation markers and leukocyte adhesion, which in turn increased virus replication and cytotoxicity in endothelial cells. In vivo RAMBO treatment of subcutaneously implanted sarcoma tumors significantly reduced tumor growth in mice bearing sarcoma compared to rHSVQ. In addition, histological analysis of RAMBO-treated tumor tissues revealed large areas of necrosis and a statistically significant reduction in microvessel density (MVD). This study provides strong preclinical evidence of the therapeutic benefit for the use of RAMBO virus as a treatment option for highly vascularized tumors.
Highlights
Angiogenesis—the formation of new blood vessels—is a well-established property of solid tumors and is essential for their growth and metastasis [1]
We have previously shown that oncolytic herpes simplex virus-1 treatment in mice bearing highly vascularized GBM tumors induces endothelial cell activation, thereby increasing blood vessel permeability and leukocyte adhesion [11]
To evaluate the spread of oncolytic herpes simplex virus-1 (oHSV) in tumors, we utilized intravital imaging of intracranial RFP-expressing primary GBM12 (GBM12-RFP) tumors in mice. These mice were infected with GFP-expressing control oHSV, and vasculature was visualized by perfusion with 1% Alexa Fluor 647-conjugated BSA fluorescent dye given intravenously at the time of imaging
Summary
Angiogenesis—the formation of new blood vessels—is a well-established property of solid tumors and is essential for their growth and metastasis [1]. Multiple efforts have been made to target this pathway for the treatment of heavily vascularized malignant tumors, there has been little success in finding effective treatment options which strengthens the need for novel strategies [2,3]. Soft tissue sarcoma (STS) represents a rare malignant heterogeneous group of tumors that typically develops in the tissues that surround, connect, and support other body structures in adults [4]. GBM is a highly vascularized primary brain tumor in adults with extremely poor patient survival rate [2,3]. There is an urgent need for novel therapies to improve the survival rate of both STS and GBM [6]
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