title: Preclinical testing of recombinant adenoviral herpes simplex virus-thymidine kinase gene therapy for central nervous system malignancies.
abstract: OBJECTIVE
  Adenoviral gene transfer and killing efficiency using the thymidine kinase (TK)/ganciclovir (GCV) mechanism was evaluated in human cancer cells occurring as central nervous system tumors. The effectiveness of this approach was tested in vitro and in experimental models for brain tumor and leptomeningeal metastases in rats in vivo. Recombinant adenoviruses with different promoters were compared.
  
  
  METHODS
  Adenoviral vectors harboring a marker (lacZ) or a TK gene were constructed. Transcription of genes was under the control of either the adenovirus Type 2 major late promoter (MLP) or the human cytomegalovirus (CMV) immediate early gene promoter. lacZ expression and GCV killing efficiency after TK gene transfer in several human tumor cells was evaluated in vitro. The 9L rat brain tumor and leptomeningeal metastases models were used to determine the effectiveness of adeno-TK and subsequent GCV treatment in vivo. MLP and CMV containing adenoviral vectors were compared.
  
  
  RESULTS
  Gene expression and the killing of tumor cells were very efficient in all human tumor cell lines tested. The adenovirus containing the CMV promoter showed cytopathic effects in cultured tumor cells at high multiplicity of infections but also greater cell killing efficiency after TK/GCV treatment, as compared to the MLP promoter. Although both the MLP and CMV vectors showed a significant dose-dependent therapeutic effect, animals treated with recombinant adenovirus containing the CMV promoter showed significantly longer survival time (brain tumors) or symptom-free periods (leptomeningeal metastases).
  
  
  CONCLUSIONS
  This study demonstrates the therapeutic efficiency and feasibility of the TK/GCV approach in experimental brain tumors and leptomeningeal metastases. It also demonstrates that the promoter driving the transgene in an adenoviral vector influences toxicity and efficiency of treatment.
authors.affiliation: Department of Neurosurgery, University Hospital Rotterdam, The Netherlands.
authors.forename: A J
authors.initials: AJ
authors.lastname: Vincent
authors.forename: M C
authors.initials: MC
authors.lastname: Esandi
authors.forename: C J
authors.initials: CJ
authors.lastname: Avezaat
authors.forename: C J
authors.initials: CJ
authors.lastname: Vecht
authors.forename: P
authors.initials: P
authors.lastname: Sillevis Smitt
authors.forename: D W
authors.initials: DW
authors.lastname: van Bekkum
authors.forename: D
authors.initials: D
authors.lastname: Valerio
authors.forename: P M
authors.initials: PM
authors.lastname: Hoogerbrugge
authors.forename: A
authors.initials: A
authors.lastname: Bout
mesh_terms: D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D000998:Antiviral Agents / Q000627:therapeutic use; D001099:Arachnoid; D001932:Brain Neoplasms / Q000628:therapy; D016543:Central Nervous System Neoplasms / Q000628:therapy*; D003587:Cytomegalovirus / Q000235:genetics; D015774:Ganciclovir / Q000627:therapeutic use; D018628:Gene Dosage; D015316:Genetic Therapy; D006801:Humans; D008577:Meningeal Neoplasms / Q000556:secondary / Q000628:therapy; D010841:Pia Mater; D011401:Promoter Regions, Genetic; D051381:Rats; D011995:Recombination, Genetic; D018139:Simplexvirus / Q000201:enzymology* / Q000235:genetics*; D016019:Survival Analysis; D013937:Thymidine Kinase / Q000235:genetics*; D014407:Tumor Cells, Cultured
chemical_list: D000998:Antiviral Agents; D013937:Thymidine Kinase; D015774:Ganciclovir