title: Manipulation of gene expression by an ecdysone-inducible gene switch in tumor xenografts.
abstract: BACKGROUND
  Rapid, robust and reversible induction of transgene expression would significantly facilitate cancer gene therapy as well as allow the in vivo functional study of newly discovered genes in tumor formation and progression. The popularity of the ecdysone inducible gene switch system has led us to investigate whether such a system can successfully regulate gene expression in a syngeneic tumor system in vivo.
  
  
  RESULTS
  MBT-2 and Panc02 carcinoma cells were transfected with components of a modification of the ecdysone switch system driving firefly luciferase (F-Luc). In vitro luciferase expression +/- ecdysone analog GS-E indicated a robust induction with minimal baseline activity and complete decay after 24 hours without drug. In vitro selection of MBT-2 transfected cell clones which had complete absence of F-Luc expression in the absence of stimulation but which expressed this gene at high levels in response to GS-E were chosen for in vivo evaluation. Tumors from engineered MBT-2 cells were grown to 5 mm in diameter prior to GS-E administration, animals euthanized and tumors removed at 6, 12 and 24 hours after GS-E administration and assayed for F-Luc activity. GS-E resulted in a maximal induction of F-Luc activity at 6 hours in tumor tissue with almost complete reversion to control levels by 12 hours.
  
  
  CONCLUSIONS
  This study is the first demonstration that robust and reversible transgene expression in tumors is feasible using the ecdysone system, allowing future rapid in vivo functional characterization of gene function or gene therapy applications.
authors.affiliation: 1Upstate Biotechnology Inc., Charlottesville, Virginia, USA. lkarns@argonex.com
authors.forename: L R
authors.initials: LR
authors.lastname: Karns
authors.forename: A
authors.initials: A
authors.lastname: Kisielewski
authors.forename: K M
authors.initials: KM
authors.lastname: Gulding
authors.forename: J M
authors.initials: JM
authors.lastname: Seraj
authors.forename: D
authors.initials: D
authors.lastname: Theodorescu
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D004440:Ecdysone / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D017930:Genes, Reporter / Q000235:genetics; D005818:Genetic Engineering; D015316:Genetic Therapy / Q000379:methods; D049452:Green Fluorescent Proteins; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008164:Luminescent Proteins / Q000032:analysis / Q000235:genetics; D051379:Mice; D009368:Neoplasm Transplantation; D010190:Pancreatic Neoplasms / Q000235:genetics; D019076:Transgenes / Q000235:genetics; D001749:Urinary Bladder Neoplasms / Q000235:genetics*
chemical_list: D008164:Luminescent Proteins; D049452:Green Fluorescent Proteins; D004440:Ecdysone; D008156:Luciferases