Vaccinia as a vector for tumor-directed gene therapy: biodistribution of a thymidine kinase-deleted mutant

Cancer Gene Ther. 2000 Jan;7(1):66-73. doi: 10.1038/sj.cgt.7700075.


Tumor-directed gene therapy, such as "suicide gene" therapy, requires high levels of gene expression in a high percentage of tumor cells in vivo to be effective. Current vector strategies have been ineffective in achieving these goals. This report introduces the attenuated (thymidine kinase (TK)-negative) replication-competent vaccinia virus (VV) as a potential vector for tumor-directed gene therapy by studying the biodistribution of VV in animal tumor models. A TK-deleted recombinant VV (Western Reserve strain) expressing luciferase on a synthetic promoter was constructed. Luciferase activity was measured in vitro after transduction of a variety of human and murine tumor cell lines and in vivo after intraperitoneal (i.p.) delivery in C57BL/6 mice with 7-day i.p. tumors (10(6) MC-38 cells). Three other in vivo tumor models were examined for tumor-specific gene expression after intravenous delivery of VV (human melanoma in nude mice, adenocarcinoma liver metastasis in immunocompetent mice, and subcutaneous sarcoma in the rat). In addition, a replication-incompetent vaccinia (1 microg of psoralen and ultraviolet light, 365 nm, 4 minutes) was tested in vitro and in vivo and compared with active virus. Luciferase activity in i.p. tumors at 4 days after i.p. injection of VV was >7000-fold higher than lung, >3000-fold higher than liver, and >250-fold higher than ovary. In addition, intravenous injection of VV resulted in markedly higher tumor luciferase activity compared with any other organ in every model tested (up to 188,000-fold higher than liver and 77,000-fold higher than lung). Inactivation of the virus resulted in negligible gene expression in vivo. In summary, VV has a high transduction efficiency in tumor cells with high levels of gene expression. The results suggest a selective in vivo replication of TK-deleted VV in tumor cells. Replication competent, TK-deleted VV appears to be an ideal vector for testing the in vivo delivery of toxic genes to tumor cells.

MeSH terms

  • Animals
  • Biomarkers, Tumor
  • Disease Models, Animal
  • Ficusin / pharmacology
  • Gene Expression / drug effects
  • Gene Expression / radiation effects
  • Genetic Therapy*
  • Genetic Vectors / genetics*
  • HT29 Cells
  • Humans
  • Luciferases / biosynthesis
  • Mice
  • Mice, Inbred C57BL
  • Mice, Nude
  • Mutation
  • Neoplasms, Experimental / genetics
  • Neoplasms, Experimental / metabolism
  • Neoplasms, Experimental / therapy*
  • Photosensitizing Agents / pharmacology
  • Rats
  • Rats, Inbred F344
  • Thymidine Kinase / genetics*
  • Thymidine Kinase / metabolism
  • Transfection / drug effects
  • Transfection / radiation effects
  • Tumor Cells, Cultured
  • Ultraviolet Rays
  • Vaccinia virus / genetics*
  • Virus Replication


  • Biomarkers, Tumor
  • Photosensitizing Agents
  • Luciferases
  • Thymidine Kinase
  • Ficusin