title: Reporter gene imaging: effects of ganciclovir treatment on nucleoside uptake, hypoxia and perfusion in a murine gene therapy tumour model that expresses herpes simplex type-1 thymidine kinase.
abstract: Perfusion, hypoxia and nucleoside uptake during ganciclovir therapy were determined in a murine HSV-1 TK-expressing tumour model (KBALB-STK). HSV-1 TK mRNA transcription in this cell line was confirmed by RT-PCR. BALB/c mice bearing KBALB-STK tumours accumulated (E)-5-(2-[125I]iodovinyl)-2'-fluoro-2'-deoxyuridine ([125I]IVFRU) (2.54% injected dose.g-1) and could be readily detected with planar imaging following administration of [131I]IVFRU. However, a single dose of ganciclovir (100 mg.kg-1 intraperitoneally) decreased tumour uptake of [125I]IVFRU to 0.33% injected dose.g-1. Subsequent single daily doses of ganciclovir over 3 consecutive days had a negligible effect on [125I]IVFRU uptake, which remained low. Tumour perfusion during 3 days of ganciclovir treatment was monitored with intravenous [99Tcm]HMPAO. Tumour perfusion increased from day 0 (no ganciclovir treatment) with 1.83% injected dose.g-1 tumour, to a maximum at day 2 (3.77% injected dose.g-1). In the same animals, accumulation of [3H]misonidazole decreased from 0.70% injected dose.g-1 at day 0 to a minimum at day 3 (0.24% injected dose.g-1), indicating that tumour tissue had become less hypoxic over the ganciclovir regimen. The uptake of [125I]IVFRU into the acid insoluble fraction of KBALB-STK cells in vitro in the presence of ganciclovir (2.0 microM) was completely inhibited, leading to a 57% decrease in total cellular accumulation of radioactivity. However, cytosolic entrapment of [125I]IVFRU was not affected by the presence of ganciclovir. These results indicate that the mechanisms leading to IVFRU exclusion during ganciclovir treatment of HSV-1 TK-expressing tumours can be attributed, at least partially, to inhibition of [125I]IVFRU-nucleotide incorporation into DNA.
authors.affiliation: Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Canada.
authors.forename: K W
authors.initials: KW
authors.lastname: Morin
authors.forename: E E
authors.initials: EE
authors.lastname: Knaus
authors.forename: L I
authors.initials: LI
authors.lastname: Wiebe
authors.forename: H
authors.initials: H
authors.lastname: Xia
authors.forename: A J
authors.initials: AJ
authors.lastname: McEwan
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000032:analysis / Q000493:pharmacokinetics*; D015687:Cell Hypoxia / Q000187:drug effects; D005467:Floxuridine / Q000031:analogs & derivatives* / Q000032:analysis / Q000493:pharmacokinetics; D015774:Ganciclovir / Q000627:therapeutic use*; D017930:Genes, Reporter; D015316:Genetic Therapy; D018259:Herpesvirus 1, Human / Q000235:genetics*; D007457:Iodine Radioisotopes; D051379:Mice; D011877:Radionuclide Imaging; D012513:Sarcoma, Experimental / Q000000981:diagnostic imaging / Q000628:therapy*; D019690:Technetium Tc 99m Exametazime; D013937:Thymidine Kinase / Q000032:analysis* / Q000235:genetics*; D014407:Tumor Cells, Cultured
chemical_list: D000998:Antiviral Agents; D007457:Iodine Radioisotopes; D005467:Floxuridine; C060868:5-(2-iodovinyl)-1-(2'-fluoro-2'-deoxyuridine); D019690:Technetium Tc 99m Exametazime; D013937:Thymidine Kinase; D015774:Ganciclovir