title: Intracellular efficacy of tumor-targeting group I intron-based trans-splicing ribozyme.
abstract: BACKGROUND
  Group I intron-based trans-splicing ribozyme, which can specifically reprogram human telomerase reverse transcriptase (hTERT) RNA, could be a useful tool for tumor-targeted gene therapy. In the present study, the therapeutic feasibility of this ribozyme was investigated by analyzing trans-splicing efficacy in vivo as well as in cells.
  
  
  METHODS
  We assessed transgene activation, degree of ribozyme expression, targeted hTERT mRNA level, or the level of trans-splicing products in hTERT(+) cells or in human tumor nodules xenografted in animals after ribozyme administration.
  
  
  RESULTS
  The activity and efficacy of the trans-splicing ribozyme in cells was dependent on the amount of endogenous hTERT mRNA and/or the accumulation of ribozyme RNA in cells. Intracellular activity of the ribozyme reached a plateau when no more targetable substrate mRNA was available or the ribozyme RNA level was fully saturated. In addition, the efficacy of ribozyme in xenografted tumor tissues was dependent on the dose of the delivered ribozyme-encoding adenoviral vector, indicating the potential of the ribozyme expression level as a determining factor for the in vivo efficacy of the trans-splicing ribozyme. On the basis of these results, we enhanced the intracellular ribozyme activity by increasing the ribozyme expression level transcriptionally and/or post-transcriptionally.
  
  
  CONCLUSIONS
  We analyzed ribozyme efficacy and determined the most influential factors of its trans-splicing reaction in mammalian cell lines as well as in vivo. The present study could provide insights into the optimization of the trans-splicing ribozyme-based RNA replacement approach to cancer treatment.
authors.affiliation: Department of Molecular Biology, Dankook University, Yongin, Korea.
authors.forename: Byung-Su
authors.initials: BS
authors.lastname: Kwon
authors.forename: Jin Sook
authors.initials: JS
authors.lastname: Jeong
authors.forename: You Sub
authors.initials: YS
authors.lastname: Won
authors.forename: Chang Ho
authors.initials: CH
authors.lastname: Lee
authors.forename: Kyung-Sik
authors.initials: KS
authors.lastname: Yoon
authors.forename: Min
authors.initials: M
authors.lastname: Hyung Jung
authors.forename: In-Hoo
authors.initials: IH
authors.lastname: Kim
authors.forename: Seong-Wook
authors.initials: SW
authors.lastname: Lee
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D005822:Genetic Vectors / Q000235:genetics; D057809:HEK293 Cells; D019073:HT29 Cells; D006801:Humans; D042541:Intracellular Space / Q000201:enzymology*; D007438:Introns / Q000235:genetics*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009369:Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D016337:RNA, Catalytic / Q000235:genetics* / Q000378:metabolism*; D019098:Telomerase / Q000378:metabolism; D014183:Transplantation, Heterologous
chemical_list: D016337:RNA, Catalytic; C509186:TERT protein, human; D019098:Telomerase