title: High efficiency of alphaviral gene transfer in combination with 5-fluorouracil in a mouse mammary tumor model.
abstract: BACKGROUND
  The combination of virotherapy and chemotherapy may enable efficient tumor regression that would be unachievable using either therapy alone. In this study, we investigated the efficiency of transgene delivery and the cytotoxic effects of alphaviral vector in combination with 5-fluorouracil (5-FU) in a mouse mammary tumor model (4 T1).
  
  
  METHODS
  Replication-deficient Semliki Forest virus (SFV) vectors carrying genes encoding fluorescent proteins were used to infect 4 T1 cell cultures treated with different doses of 5-FU. The efficiency of infection was monitored via fluorescence microscopy and quantified by fluorometry. The cytotoxicity of the combined treatment with 5-FU and alphaviral vector was measured using an MTT-based cell viability assay. In vivo experiments were performed in a subcutaneous 4 T1 mouse mammary tumor model with different 5-FU doses and an SFV vector encoding firefly luciferase.
  
  
  RESULTS
  Infection of 4 T1 cells with SFV prior to 5-FU treatment did not produce a synergistic anti-proliferative effect. An alternative treatment strategy, in which 5-FU was used prior to virus infection, strongly inhibited SFV expression. Nevertheless, in vivo experiments showed a significant enhancement in SFV-driven transgene (luciferase) expression upon intratumoral and intraperitoneal vector administration in 4 T1 tumor-bearing mice pretreated with 5-FU: here, we observed a positive correlation between 5-FU dose and the level of luciferase expression.
  
  
  CONCLUSIONS
  Although 5-FU inhibited SFV-mediated transgene expression in 4 T1 cells in vitro, application of the drug in a mouse model revealed a significant enhancement of intratumoral transgene synthesis compared with 5-FU untreated mice. These results may have implications for efficient transgene delivery and the development of potent cancer treatment strategies using alphaviral vectors and 5-FU.
authors.affiliation: Department of Cell Biology, Biomedical Research and Study Centre, Ratsupites Str,, 1, Riga LV-1067, Latvia. anna@biomed.lu.lv.
authors.forename: Anna
authors.initials: A
authors.lastname: Zajakina
authors.forename: Jelena
authors.initials: J
authors.lastname: Vasilevska
authors.forename: Dmitry
authors.initials: D
authors.lastname: Zhulenkovs
authors.forename: Dace
authors.initials: D
authors.lastname: Skrastina
authors.forename: Artjoms
authors.initials: A
authors.lastname: Spaks
authors.forename: Aiva
authors.initials: A
authors.lastname: Plotniece
authors.forename: Tatjana
authors.initials: T
authors.lastname: Kozlovska
mesh_terms: D000524:Alphavirus / Q000235:genetics*; D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D003131:Combined Modality Therapy; D004195:Disease Models, Animal; D005260:Female; D005472:Fluorouracil / Q000008:administration & dosage / Q000494:pharmacology*; D018014:Gene Transfer Techniques; D017930:Genes, Reporter; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000235:genetics*; D015674:Mammary Neoplasms, Animal / Q000235:genetics* / Q000473:pathology / Q000628:therapy; D051379:Mice; D012672:Semliki forest virus / Q000235:genetics; D014161:Transduction, Genetic; D019076:Transgenes
chemical_list: D005472:Fluorouracil