title: Characterization of HIV-1 TAT peptide as an enhancer of HSV-TK/GCV cancer gene therapy.
abstract: Cancer suicide gene therapy based on herpes simplex virus type I thymidine kinase (HSV-TK) and ganciclovir (GCV) suffers from the lack of efficacy in clinical use, which is mostly due to low gene-transfer efficiency and absence of bystander effect in tumors. We have previously demonstrated the enhancement of GCV cytotoxicity by fusing the HSV-TK with the cell penetrating peptide from HIV-1 transactivator protein transduction domain (TAT PTD). Despite the earlier promising results, we found that the triple fusion protein HIV-1 transactivator protein transduction domain-thymidine kinase suicide gene-green fluorescent protein marker gene (TAT-TK-GFP) increased GCV cytotoxicity only in 3/12 of different human tumor cell lines. Extended GCV exposure enhanced the cytotoxic effect of HSV-TK/GCV gene therapy, but the difference between TK-GFP and TAT-TK-GFP was not statistically significant. The modest improvement on cell killing mediated by TAT PTD in Chinese hamster ovary cells appeared to be associated with cell-surface heparan sulfate proteoglycan (HSPG) composition. However, TAT-mediated increased cell death did not correlate with the density of cell-surface HSPG expression in different tumor cell lines. In conclusion, although some degree of enhancement by TAT was shown in certain tumor cells in vitro, it is unlikely that TAT peptide linked to a suicide protein could be a useful booster of in vivo gene therapy trials.
authors.affiliation: Department of Biotechnology and Molecular Medicine, AI Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, Finland. outi.rautsi@uku.fi
authors.forename: O
authors.initials: O
authors.lastname: Rautsi
authors.forename: S
authors.initials: S
authors.lastname: Lehmusvaara
authors.forename: A
authors.initials: A
authors.lastname: Ketola
authors.forename: A-M
authors.initials: AM
authors.lastname: Määttä
authors.forename: J
authors.initials: J
authors.lastname: Wahlfors
authors.forename: R
authors.initials: R
authors.lastname: Pellinen
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000627:therapeutic use; D016466:CHO Cells; D016923:Cell Death / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D015774:Ganciclovir / Q000627:therapeutic use*; D015316:Genetic Therapy / Q000379:methods*; D018259:Herpesvirus 1, Human / Q000235:genetics*; D006801:Humans; D009369:Neoplasms / Q000235:genetics* / Q000628:therapy*; D010446:Peptide Fragments / Q000627:therapeutic use*; D013937:Thymidine Kinase / Q000235:genetics* / Q000627:therapeutic use; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000737:chemistry / Q000627:therapeutic use*
chemical_list: D000998:Antiviral Agents; D010446:Peptide Fragments; D054322:tat Gene Products, Human Immunodeficiency Virus; D013937:Thymidine Kinase; D015774:Ganciclovir