Abstract
IntroductionOncolytic viruses show promise for treating cancer. However, to assess therapeutic efficacy and potential toxicity, a noninvasive imaging modality is needed. This study aimed to determine if insertion of the human sodium iodide symporter (hNIS) cDNA as a marker for non-invasive imaging of virotherapy alters the replication and oncolytic capability of a novel vaccinia virus, GLV-1h153.MethodsGLV-1h153 was modified from parental vaccinia virus GLV-1h68 to carry hNIS via homologous recombination. GLV-1h153 was tested against human pancreatic cancer cell line PANC-1 for replication via viral plaque assays and flow cytometry. Expression and transportation of hNIS in infected cells was evaluated using Westernblot and immunofluorescence. Intracellular uptake of radioiodide was assessed using radiouptake assays. Viral cytotoxicity and tumor regression of treated PANC-1tumor xenografts in nude mice was also determined. Finally, tumor radiouptake in xenografts was assessed via positron emission tomography (PET) utilizing carrier-free 124I radiotracer.ResultsGLV-1h153 infected, replicated within, and killed PANC-1 cells as efficiently as GLV-1h68. GLV-1h153 provided dose-dependent levels of hNIS expression in infected cells. Immunofluorescence detected transport of the protein to the cell membrane prior to cell lysis, enhancing hNIS-specific radiouptake (P < 0.001). In vivo, GLV-1h153 was as safe and effective as GLV-1h68 in regressing pancreatic cancer xenografts (P < 0.001). Finally, intratumoral injection of GLV-1h153 facilitated imaging of virus replication in tumors via 124I-PET.ConclusionInsertion of the hNIS gene does not hinder replication or oncolytic capability of GLV-1h153, rendering this novel virus a promising new candidate for the noninvasive imaging and tracking of oncolytic viral therapy.
Highlights
Oncolytic viruses show promise for treating cancer
Virus and cell culture African green monkey kidney fibroblast CV-1 cells and human pancreatic ductal carcinoma PANC-1 cells were purchased from American Type Culture Collection (ATCC) (Manassas, VA) and were grown in Dulbecco’s modified Eagle’s medium (DMEM) supplemented with 1% antibiotic-antimycotic solution (Mediatech, Inc., Herndon, VA) and 10% fetal bovine serum (FBS) (Mediatech, Inc.) at 37°C under 5% CO2
Construction of the human sodium iodide symporter (hNIS) transfer vector The GLV-1h153 construct used in this study was derived from GLV-1h68 by replacing the b-glucuronidase expression cassette at the A56R locus with the hNIS expression cassette (SE-hNIS) containing the hNIS cDNA under the control of the vaccinia virus (VACV) synthetic early promoter, by homologous recombination in infected cells
Summary
To assess therapeutic efficacy and potential toxicity, a noninvasive imaging modality is needed. This study aimed to determine if insertion of the human sodium iodide symporter (hNIS) cDNA as a marker for non-invasive imaging of virotherapy alters the replication and oncolytic capability of a novel vaccinia virus, GLV-1h153. Oncolytic viral therapies have shown such success in preclinical testing as a novel cancer treatment modality that several phase I and II trials are already underway. Biopsy is the gold standard for monitoring the therapeutic effects of viral oncolysis [3,4,5]. This may be feasible in preclinical or early clinical trials, a noninvasive method facilitating ongoing monitoring of therapy is needed for human studies. A more sensitive and specific diagnostic technique to detect tumor origin and, more importantly, presence of metastases may be possible [3]
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