Effect of tumor microenvironment modulation on the efficacy of oncolytic virus therapy.
BACKGROUND
The tumor microenvironment is being increasingly recognized as an important determinant of tumor progression as well as of therapeutic response. We investigated oncolytic virus (OV) therapy-induced changes in tumor blood vessels and the impact of modulating tumor vasculature on the efficacy of oncolytic virus therapy.


METHODS
Rat glioma cells (D74/HveC) were implanted intracranially in immune-competent rats. Seven days later, the rats (groups of 3-7 rats) were treated with oncolytic virus (hrR3), and, 3 days later, brains were harvested for evaluation. Some rats were treated with angiostatic cRGD peptide 4 days before oncolytic virus treatment. Some rats were treated with cyclophosphamide (CPA), an immunosuppressant, 2 days before oncolytic virus treatment. Changes in tumor vascular perfusion were evaluated by magnetic resonance imaging of live rats and by fluorescence microscopy of tumor sections from rats perfused with Texas red-conjugated lectin immediately before euthanasia. Leukocyte infiltration in tumors was evaluated by anti-CD45 immunohistochemistry, and the presence of oncolytic virus in tumors was evaluated by viral titration. Changes in cytokine gene expression in tumors were measured by quantitative real-time polymerase chain reaction-based microarrays. Survival was analyzed by the Kaplan-Meier method. All statistical tests were two-sided.


RESULTS
Oncolytic virus treatment of experimental rat gliomas increased tumor vascular permeability, host leukocyte infiltration into tumors, and intratumoral expression of inflammatory cytokine genes, including interferon gamma (IFN-gamma). The increase in vascular permeability was suppressed in rats pretreated with cyclophosphamide. Compared with rats treated with hrR3 alone, rats pretreated with a single dose of cRGD peptide before hrR3 treatment had reduced tumor vascular permeability, leukocyte infiltration, and IFN-gamma protein levels (mean IFN-gamma level for hrR3 versus hrR3 + cRGD = 203 versus 65.6 microg/mg, difference = 137 microg/mg, 95% confidence interval = 72.7 to 202.9 microg/mg, P = .006); increased viral titers in tumor tissue; and longer median survival (21 days versus 17 days, P<.001).


CONCLUSIONS
A single dose of angiostatic cRGD peptide treatment before oncolytic virus treatment enhanced the antitumor efficacy of oncolytic virus.
Dardinger Laboratory for Neuro-oncology and Neurosciences, Department of Neurological Surgery, The Ohio State University, Columbus, OH 43210, USA.
Kazuhiko
K
Kurozumi
Jayson
J
Hardcastle
Roopa
R
Thakur
Ming
M
Yang
Gregory
G
Christoforidis
Giulia
G
Fulci
Fred H
FH
Hochberg
Ralph
R
Weissleder
William
W
Carson
E Antonio
EA
Chiocca
Balveen
B
Kaur
D020533:Angiogenesis Inhibitors / Q000494:pharmacology*; D000818:Animals; D001932:Brain Neoplasms / Q000098:blood supply* / Q000188:drug therapy / Q000473:pathology / Q000628:therapy*; D002199:Capillary Permeability; D045744:Cell Line, Tumor; D003520:Cyclophosphamide / Q000494:pharmacology; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D005453:Fluorescence; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic; D005910:Glioma / Q000098:blood supply* / Q000188:drug therapy / Q000473:pathology / Q000628:therapy*; D006801:Humans; D007150:Immunohistochemistry; D007166:Immunosuppressive Agents / Q000494:pharmacology; D007249:Inflammation / Q000188:drug therapy; D053208:Kaplan-Meier Estimate; D007962:Leukocytes / Q000187:drug effects; D008279:Magnetic Resonance Imaging; D008297:Male; D008833:Microcirculation; D008853:Microscopy / Q000379:methods; D050130:Oncolytic Virotherapy; D010456:Peptides, Cyclic / Q000494:pharmacology*; D011897:Random Allocation; D051381:Rats; D011916:Rats, Inbred F344; D016896:Treatment Outcome
D020533:Angiogenesis Inhibitors; D007166:Immunosuppressive Agents; D010456:Peptides, Cyclic; C507169:cyclic arginine-glycine-aspartic acid peptide; D003520:Cyclophosphamide