title: Potentiation of ganciclovir toxicity in the herpes simplex virus thymidine kinase/ganciclovir administration system by ponicidin.
abstract: The herpes simplex virus thymidine kinase (HSV-TK)/ganciclovir (GCV) administration system is commonly used in gene therapy trials. We have evaluated the effect of ponicidin, a diterpenoid isolated from a plant, Rabdosia ternifolia, on the cell-killing activity of the anti-herpes drugs acyclovir (ACV) and GCV. Ponicidin preferentially activated HSV-1-specific TK but not cellular kinases. In HSV-infected cells, ponicidin significantly accumulated the phosphorylated metabolites of GCV and suppressed the extracellular release of GCV. These data suggested that the cytotoxicities of ACV and GCV in HSV-TK-expressing cells might be potentiated by ponicidin. After transfected with the HSV-1 TK gene, COS-1 and several human cancer cells became highly sensitive to the cytotoxic properties of the nucleoside analogs. When ponicidin at the concentration without antiviral activities (0.2 microg/mL) was combined with ACV or GCV, the cytotoxic levels in HSV-TK-expressing cells were enhanced by 3- to 87-fold and 5- to 52-fold, respectively, compared with the nucleoside alone. When the stability of the bioactivity of ponicidin in the blood of mice was evaluated, the substance showed relatively long-lasting effects on the potentiation of the anti-herpetic and cytotoxic activities of GCV after intravenous administration. These data suggest that the combined use of ponicidin with GCV will be effective for cancer gene therapy, because high cytotoxicity in viral TK-expressing cells should yield more rapid and enhanced tumor elimination.
authors.affiliation: Department of Virology, Toyama Medical and Pharmaceutical University, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Hayashi
authors.forename: T
authors.initials: T
authors.lastname: Hayashi
authors.forename: H D
authors.initials: HD
authors.lastname: Sun
authors.forename: Y
authors.initials: Y
authors.lastname: Takeda
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D000998:Antiviral Agents / Q000494:pharmacology; D019556:COS Cells; D002455:Cell Division / Q000187:drug effects; D002522:Chlorocebus aethiops; D004224:Diterpenes / Q000494:pharmacology*; D004354:Drug Screening Assays, Antitumor; D004357:Drug Synergism; D015774:Ganciclovir / Q000378:metabolism / Q000494:pharmacology*; D015316:Genetic Therapy; D006367:HeLa Cells; D006801:Humans; D010766:Phosphorylation / Q000187:drug effects; D018139:Simplexvirus / Q000201:enzymology; D013937:Thymidine Kinase / Q000235:genetics / Q000627:therapeutic use*; D014162:Transfection; D014316:Tritium
chemical_list: D000970:Antineoplastic Agents; D000998:Antiviral Agents; D004224:Diterpenes; D014316:Tritium; C090365:ponicidin; D013937:Thymidine Kinase; D015774:Ganciclovir