title: A mutant herpes simplex virus type 1 thymidine kinase reporter gene shows improved sensitivity for imaging reporter gene expression with positron emission tomography.
abstract: We are developing assays for noninvasive, quantitative imaging of reporter genes with positron emission tomography (PET), for application both in animal models and in human gene therapy. We report here a method to improve the detection of lower levels of PET reporter gene expression by utilizing a mutant herpes simplex virus type 1 thymidine kinase (HSV1-sr39tk) as a PET reporter gene. The HSV1-sr39tk mutant was identified from a library of site-directed mutants. Accumulation (net uptake) of the radioactively labeled substrates [8-(3)H]penciclovir ([8-(3)H]PCV), and 8-[(18)F]fluoropenciclovir (FPCV) in C6 rat glioma cells expressing HSV1-sr39tk is increased by a factor of approximately 2.0 when compared with C6 cells expressing wild-type HSV1-tk. The increased imaging sensitivity of HSV1-sr39tk when FPCV is used is also demonstrated in vivo both with tumor cells stably transfected with either HSV1-tk or HSV1-sr39tk, and after hepatic delivery of HSV1-tk or HSV1-sr39tk by using adenoviral vectors. The use of HSV1-sr39tk as a PET reporter gene and FPCV as a PET reporter probe results in significantly enhanced sensitivity for imaging reporter gene expression in vivo.
authors.affiliation: The Crump Institute for Biological Imaging, University of California/Department of Energy Laboratory of Structural Biology and Molecular Medicine, University of California School of Medicine, Los Angeles, CA 90095-1770, USA. sgambhir@mednet.ucla.edu
authors.forename: S S
authors.initials: SS
authors.lastname: Gambhir
authors.forename: E
authors.initials: E
authors.lastname: Bauer
authors.forename: M E
authors.initials: ME
authors.lastname: Black
authors.forename: Q
authors.initials: Q
authors.lastname: Liang
authors.forename: M S
authors.initials: MS
authors.lastname: Kokoris
authors.forename: J R
authors.initials: JR
authors.lastname: Barrio
authors.forename: M
authors.initials: M
authors.lastname: Iyer
authors.forename: M
authors.initials: M
authors.lastname: Namavari
authors.forename: M E
authors.initials: ME
authors.lastname: Phelps
authors.forename: H R
authors.initials: HR
authors.lastname: Herschman
mesh_terms: D000212:Acyclovir / Q000378:metabolism / Q000493:pharmacokinetics; D000256:Adenoviridae / Q000378:metabolism; D000818:Animals; D000998:Antiviral Agents / Q000378:metabolism; D015152:Blotting, Northern; D015153:Blotting, Western; D002851:Chromatography, High Pressure Liquid; D004926:Escherichia coli / Q000378:metabolism; D005461:Fluorine / Q000493:pharmacokinetics; D015774:Ganciclovir / Q000378:metabolism; D017930:Genes, Reporter; D018259:Herpesvirus 1, Human / Q000201:enzymology* / Q000235:genetics*; D008099:Liver / Q000378:metabolism; D051379:Mice; D016296:Mutagenesis; D011355:Prodrugs / Q000378:metabolism; D051381:Rats; D013937:Thymidine Kinase / Q000235:genetics*; D013997:Time Factors; D014055:Tomography, Emission-Computed / Q000379:methods*; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D000998:Antiviral Agents; D011355:Prodrugs; D005461:Fluorine; D013937:Thymidine Kinase; D015774:Ganciclovir; D000212:Acyclovir