ABSTRACT
The first oncolytic virotherapy employing HSV-1 (oHSV-1) was approved recently by the FDA to treat cancer, but further improvements in efficacy are needed to eradicate challenging refractory tumors, such as glioblastomas (GBM). Microglia/macrophages comprising approximately 40% of a GBM tumor may limit virotherapeutic efficacy. Here, we show these cells suppress oHSV-1 growth in gliomas by internalizing the virus through phagocytosis. Internalized virus remained capable of expressing reporter genes while viral replication was blocked. Macrophage/microglia formed a nonpermissive OV barrier, preventing dissemination of oHSV-1 in the glioma mass. The deficiency in viral replication in microglial cells was associated with silencing of particular viral genes. Phosphorylation of STAT1/3 was determined to be responsible for suppressing oHSV-1 replication in macrophages/microglia. Treatment with the oxindole/imidazole derivative C16 rescued oHSV-1 replication in microglia/macrophages by inhibiting STAT1/3 activity. In the U87 xenograft model of GBM, C16 treatment overcame the microglia/macrophage barrier, thereby facilitating tumor regression without causing a spread of the virus to normal organs. Collectively, our results suggest a strategy to relieve a STAT1/3-dependent therapeutic barrier and enhance oHSV-1 oncolytic activity in GBM.Significance: These findings suggest a strategy to enhance the therapeutic efficacy of oncolytic virotherapy in glioblastoma. Cancer Res; 78(3); 718-30. ©2017 AACR.
Subject(s)
Brain Neoplasms/pathology , Glioblastoma/pathology , Macrophages/pathology , Microglia/pathology , Oncolytic Virotherapy , STAT1 Transcription Factor/metabolism , STAT3 Transcription Factor/metabolism , Animals , Apoptosis , Biomarkers, Tumor/metabolism , Brain Neoplasms/metabolism , Brain Neoplasms/virology , Cell Proliferation , Female , Glioblastoma/metabolism , Glioblastoma/virology , Humans , Macrophages/metabolism , Macrophages/virology , Mice , Mice, Nude , Microglia/metabolism , Microglia/virology , Oncolytic Viruses/immunology , Tumor Cells, Cultured , Xenograft Model Antitumor AssaysABSTRACT
PURPOSE: To investigate the morphologic and molecular consequences of 30- and 90-minute central retinal artery ligation (CRAL)-induced retinal ischemia, followed by 3 and 12 hours of reperfusion, and to identify potential targets for therapy. METHODS: Retinal ischemia was induced for 30 and 90 minutes by ligating the rat central retinal artery, and corresponding effects were examined histologically, immunocytochemically, and molecularly at 3 hours and 12 hours of reperfusion. Patterns of gene expression revealed significantly upregulated and downregulated genes by gene array analyses and were verified by quantitative RT-PCR. Functional pathways were correlated using gene set enrichment analysis. RESULTS: Substantial morphologic changes occurred from 3 hours to 7 days after CRAL in rats, resulting in a cellular loss in most retinal layers, particularly in inner nuclear and ganglion cell layers. After 30 minutes of CRAL and 3 hours of reperfusion, transcription-related genes such as ATF3, ID2, Klf4, BTG2, c-Fos, and c-Jun were activated. After 12 hours of reperfusion, the genes associated with kinase and caspase molecular pathways-including MAP kinases, Casp3 and Casp9-were upregulated. CRAL of 90 minutes and 3 hours of reperfusion induced glycolysis and gluconeogenesis-related genes such as G6PC. However, prolonged reperfusion of 12 hours was characterized by prominent activation of apoptosis-related genes, including Tp53, Akt1, Akt3, Pik3R1, Prkcb1, caspases (Casp3, Casp7, Casp9), and TNF. CONCLUSIONS: CRAL is a clinically relevant retinal ischemia model, and gene expression analysis can provide information regarding the molecular mechanisms underlying the pathophysiological processes during retinal ischemia. In addition, CRAL represents an effective experimental model with which to study retinal inflammation, development, aging, and, neurodegeneration.
