title: Retroviral vector-producing mesenchymal stem cells for targeted suicide cancer gene therapy.
abstract: BACKGROUND
  Mesenchymal stem cells (MSCs) are a promising vehicle for targeted cancer gene therapy because of their potential of tumor tropism. For efficient therapeutic application, we developed retroviral vector-producing MSCs that enhance tumor transduction via progeny vector production.
  
  
  METHODS
  Rat bone marrow-derived MSCs were nucleofected with the proviral plasmids (vesicular stomatitis virus-G protein-pseudotyped retroviral vector components) (VP-MSCs) or pLTR plasmid alone (non-VP-MSCs). The luciferase-based in vivo imaging system was used to assess gene expression periodically. To evaluate the anticancer effects, we administered MSCs expressing herpes simplex virus-thymidine kinase (HSV-tk) into the left ventricular cavity of nude mice engrafted with 9L glioma cells subcutaneously.
  
  
  RESULTS
  In vivo imaging revealed that administration of luciferase-expressing non-VP-MSCs enhanced the bioluminescence signal at the inoculation sites of 9L cells, whereas no accumulation was observed in mice at the site of the control Rat-1 fibroblasts. Compared to non-VP-MSCs, the administration of VP-MSCs resulted in significant augmentation of the signal with an increase in transgene copy number. Immunohistochemical analysis showed marked luciferase expression at the tumor periphery in mice injected with VP-MSCs, whereas little expression was detected in those injected with non-VP-MSCs. Under the continuous infusion of ganciclovir, systemic administration of VP-MSCs expressing HSV-tk suppressed tumor growth more effectively than non-VP-MSC administration, whereas no anticancer effect was observed without ganciclovir treatment. Furthermore, VP-MSC administration caused no transgene transduction in the normal tissues and organs.
  
  
  CONCLUSIONS
  VP-MSCs accumulated at the site of tumors after intravascular injection in tumor-bearing mice, followed by in situ gene transfer to tumors without transduction of normal organs. When applied to the HSV-tk/ganciclovir suicide gene therapy, more efficient tumor growth suppression was observed using VP-MSCs compared to non-VP-MSCs. This VP-MSC-based system has great potential for improved cancer gene therapy.
authors.affiliation: Division of Genetic Therapeutics, Center for Molecular Medicine, Jichi Medical University, Tochigi, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Uchibori
authors.forename: Takashi
authors.initials: T
authors.lastname: Okada
authors.forename: Takayuki
authors.initials: T
authors.lastname: Ito
authors.forename: Masashi
authors.initials: M
authors.lastname: Urabe
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Mizukami
authors.forename: Akihiro
authors.initials: A
authors.lastname: Kume
authors.forename: Keiya
authors.initials: K
authors.lastname: Ozawa
mesh_terms: D000818:Animals; D016923:Cell Death; D045744:Cell Line, Tumor; D002470:Cell Survival; D018628:Gene Dosage; D041722:Genes, Transgenic, Suicide; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000235:genetics*; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism*; D009369:Neoplasms / Q000235:genetics / Q000473:pathology / Q000628:therapy*; D051381:Rats; D012190:Retroviridae / Q000235:genetics*; D014161:Transduction, Genetic