title: Imaging adenoviral-mediated herpes virus thymidine kinase gene transfer and expression in vivo.
abstract: The feasibility of noninvasive imaging of adenoviral-mediated herpes virus type one thymidine kinase (HSV1-tk) gene transfer and expression was assessed in a well-studied animal model of metastatic colon carcinoma of the liver. Tumors were produced in syngeneic BALB/c mice by intrahepatic injection of colon carcinoma cells (MCA-26). Seven days later, three different doses (3 x 10(8), 1 x 10(8), and 3 x 10(7) plaque-forming units (pfu) of the recombinant adenoviral vector ADV. Rous sarcoma virus (RSV)-tk bearing the HSV1-tk gene were administered by intratumoral injection in separate groups of mice. Two control groups of tumor-bearing mice received intratumoral injections of the control adenoviral vector dl-312 or buffer alone, respectively. T2-weighted magnetic resonance (MR) images of mice were obtained before administering the virus and provided an anatomical reference of hepatic tumor localization. Eighteen h after the virus injection, one group of animals was given i.v. injections of 300 microCi of no-carrier-added 5-[131I]-2'-fluoro-1-beta-D-arabinofuranosyluracil (FIAU) and imaged 24 h later with a gamma camera. In some animals, the tumors were sampled and processed for histology and quantitative autoradiography (QAR). The gamma camera images demonstrated highly specific localization of [131I]FIAU-derived radioactivity to the area of ADV.RSV-tk-injected tumors in the liver, which was confirmed by coregistering the gamma camera and T2-weighted MR images. There was no accumulation of [131I]FIAU-derived radioactivity in tumors that were injected with the control vector or injection solution alone. A more precise distribution of radioactivity in the area of transfected tumor was obtained by histological and QAR comparisons. A heterogeneous pattern of radioactivity distribution in transfected tumors was observed. A punctate pattern of radioactivity distribution was observed in peritumoral liver tissue in animals given injections of 3 x 10(8) and 1 x 10(8) pfu of ADV.RSV-tk but not in animals given injections of 3 x 10(7) pfu nor in control animals. A QAR-microscopic comparison showed that the punctate areas of radioactivity colocalized with cholangial ducts. The level of [131I]FIAU-derived radioactivity accumulation (HSV1-tk expression) in the transfected tumors was viral dose-dependent. The viral dose-dependency of radioactivity accumulation was more pronounced in peritumoral liver, which was confirmed by reverse transcription-PCR analysis. A separate group of tumor-bearing animals received different doses of ADV.RSV-tk vector followed by treatment with ganciclovir (GCV), 10 mg/kg i.p. b.i.d. for 6 days. The ADV.RSV-tk transfected tumors significantly regressed with GCV treatment; the control tumors continued to grow. During the GCV treatment, the levels of liver transaminases (ALT and AST) were significantly increased in animals that received injections of 3 x 10(8) and 1 x 10(8) pfu of ADV.RSV-tk but not in animals that received injections of 3 x 10(7) pfu and in control animals. The observed liver toxicity confirms the results of gamma camera and QAR imaging, which demonstrated an unwanted spread of ADV.RSV-tk vector and HSV1-tk expression in peritumoral and remote liver tissue at higher doses. These and our previous results indicate that noninvasive imaging of adenoviral-mediated HSV1-tk gene expression is feasible for monitoring cancer gene therapy in patients.
authors.affiliation: Department of Neurology, Memorial Sloan Kettering Cancer Center, New York, New York 10021, USA.
authors.forename: J G
authors.initials: JG
authors.lastname: Tjuvajev
authors.forename: S H
authors.initials: SH
authors.lastname: Chen
authors.forename: A
authors.initials: A
authors.lastname: Joshi
authors.forename: R
authors.initials: R
authors.lastname: Joshi
authors.forename: Z S
authors.initials: ZS
authors.lastname: Guo
authors.forename: J
authors.initials: J
authors.lastname: Balatoni
authors.forename: D
authors.initials: D
authors.lastname: Ballon
authors.forename: J
authors.initials: J
authors.lastname: Koutcher
authors.forename: R
authors.initials: R
authors.lastname: Finn
authors.forename: S L
authors.initials: SL
authors.lastname: Woo
authors.forename: R G
authors.initials: RG
authors.lastname: Blasberg
mesh_terms: D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D001086:Arabinofuranosyluracil / Q000031:analogs & derivatives; D001345:Autoradiography; D003110:Colonic Neoplasms / Q000628:therapy*; D015774:Ganciclovir / Q000627:therapeutic use; D015870:Gene Expression; D018014:Gene Transfer Techniques; D015316:Genetic Therapy; D007457:Iodine Radioisotopes; D008279:Magnetic Resonance Imaging; D051379:Mice; D008807:Mice, Inbred BALB C; D018139:Simplexvirus / Q000201:enzymology*; D013937:Thymidine Kinase / Q000235:genetics*; D014407:Tumor Cells, Cultured
chemical_list: D007457:Iodine Radioisotopes; D001086:Arabinofuranosyluracil; C043457:fialuridine; D013937:Thymidine Kinase; D015774:Ganciclovir