title: Tumor-targeted gene therapy for nasopharyngeal carcinoma.
abstract: The unique feature of human nasopharyngeal carcinoma (NPC) is its almost universal association with the EBV, which is expressed in a latent form exclusively in cancer cells, and not in the surrounding tissues. We have exploited this differential by constructing a novel replication-deficient adenovirus vector (ad5.oriP) in which transgene expression is under the transcriptional regulation of the family of repeats domain of the origin of replication (oriP) of EBV. When EBNA1, one of the latent gene products of EBV, binds to the family of repeats sequence, this activates transcription of downstream genes. Vector constructs were made using the beta-galactosidase and luciferase reporter genes (ad5oriP.betagal and ad5oriP.luc) or the p53 tumor suppressor gene (ad5oriP.p53). 5-Bromo-4-chloro-3-indolyl-beta-D-galactopyranoside staining demonstrated extensive expression only in EBV-positive NPC cells, specifically in response to the presence of EBNA1. The relative difference in expression between EBV-positive and -negative cell lines is approximately 1000-fold. This selective expression was corroborated in EBV-positive and -negative tumor models, along with an absence of transgene expression in the host liver. Significant cytotoxicity was achieved using the adv.oriP.p53 therapeutic gene only in EBV-positive NPC cells, which was enhanced with the addition of ionizing radiation. Cytotoxicity was mediated primarily by induction of apoptosis. These results demonstrate that the oriP sequence can achieve high levels of gene expression targeted specifically to EBV-positive NPC cells in the context of the adv vector. This has now provided the tumor-specific expression system from which additional interventions can be evaluated in future treatment strategies for patients with nasopharyngeal cancers.
authors.affiliation: Department of Radiation Oncology, Princess Margaret Hospital/Ontario Cancer Institute, University Health Network, Toronto, Ontario, M5G 2M9 Canada.
authors.forename: Jian-Hua
authors.initials: JH
authors.lastname: Li
authors.forename: Marie
authors.initials: M
authors.lastname: Chia
authors.forename: Wei
authors.initials: W
authors.lastname: Shi
authors.forename: D
authors.initials: D
authors.lastname: Ngo
authors.forename: Craig A
authors.initials: CA
authors.lastname: Strathdee
authors.forename: Dolly
authors.initials: D
authors.lastname: Huang
authors.forename: Henry
authors.initials: H
authors.lastname: Klamut
authors.forename: Fei-Fei
authors.initials: FF
authors.lastname: Liu
mesh_terms: D000256:Adenoviridae / Q000235:genetics / Q000502:physiology; D000818:Animals; D017209:Apoptosis / Q000235:genetics; D019309:Epstein-Barr Virus Nuclear Antigens / Q000235:genetics; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000235:genetics; D004854:Herpesvirus 4, Human / Q000235:genetics; D006801:Humans; D051379:Mice; D016513:Mice, SCID; D009303:Nasopharyngeal Neoplasms / Q000235:genetics* / Q000628:therapy / Q000821:virology*; D018741:Replication Origin / Q000235:genetics; D019076:Transgenes; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis / Q000235:genetics; D014779:Virus Replication; D023041:Xenograft Model Antitumor Assays; D001616:beta-Galactosidase / Q000096:biosynthesis / Q000235:genetics
chemical_list: D019309:Epstein-Barr Virus Nuclear Antigens; D016159:Tumor Suppressor Protein p53; D001616:beta-Galactosidase; C417029:EBV-encoded nuclear antigen 1