title: miR-122a-regulated expression of a suicide gene prevents hepatotoxicity without altering antitumor effects in suicide gene therapy.
abstract: The combined use of adenovirus (Ad) vectors expressing herpes simplex virus thymidine kinase (HSVtk) and ganciclovir (GCV) offers a potential therapeutic strategy against cancer. However, intratumorally injected Ad vectors are disseminated into the systemic circulation and efficiently transduce the liver, resulting in severe hepatotoxicity. In order to overcome this problem, an Ad vector carrying a microRNA (miRNA)-regulated expression system was developed by inserting into the 3'-untranslated region (3'-UTR) of the expression cassette four tandem copies of sequences with perfect complementarity to miR-122a, which exhibits liver-specific expression. Transgene expression from the Ad vector carrying the miR-122a target sequences was 7- to 70-fold lower in cells with high miR-122a expression as compared to expression from a conventional Ad vector. Intratumoral injection of the Ad vector containing the miR-122a target sequences resulted in a 130- to 1,500-fold reduction in hepatic transgene products (without affecting the transgene expression in the tumor) when compared with those from a conventional Ad vector. In suicide gene therapy, the inclusion of the miR-122a target sequences in the HSVtk expression cassette achieved not only significant antitumor effects, but also a dramatic reduction in HSVtk/GCV-induced hepatotoxicity. These results indicate that Ad vectors that mediate miR-122a-regulated HSVtk expression provide a safe and efficient suicide gene therapy strategy.
authors.affiliation: Laboratory of Gene Transfer and Regulation, National Institute of Biomedical Innovation, Osaka, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Suzuki
authors.forename: Fuminori
authors.initials: F
authors.lastname: Sakurai
authors.forename: Shin-ichiro
authors.initials: S
authors.lastname: Nakamura
authors.forename: Emi
authors.initials: E
authors.lastname: Kouyama
authors.forename: Kenji
authors.initials: K
authors.lastname: Kawabata
authors.forename: Masuo
authors.initials: M
authors.lastname: Kondoh
authors.forename: Kiyohito
authors.initials: K
authors.lastname: Yagi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Mizuguchi
mesh_terms: D020413:3' Untranslated Regions; D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology*; D041722:Genes, Transgenic, Suicide; D015316:Genetic Therapy; D005822:Genetic Vectors; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D035683:MicroRNAs / Q000502:physiology*; D018139:Simplexvirus / Q000201:enzymology; D013937:Thymidine Kinase / Q000235:genetics
chemical_list: D020413:3' Untranslated Regions; D035683:MicroRNAs; D013937:Thymidine Kinase