Glioma cells transduced with an Escherichia coli CD/HSV-1 TK fusion gene exhibit enhanced metabolic suicide and radiosensitivity

Hum Gene Ther. 1997 Jan 1;8(1):73-85. doi: 10.1089/hum.1997.8.1-73.


To ascertain whether concomitant expression of Escherichia coli deaminase (CD) and herpes simplex virus type-1 thymidine kinase (HSV-1 TK) could mediate greater levels of cytotoxicity beyond that observed with either suicide gene alone, 9L gliosarcoma cells were transduced with a retrovirus encoding a CD/HSV-1 TK fusion gene. The resultant CD/HSV-1 TK fusion protein (CDglyTK) was found to be bifunctional via CD and HSV-1 TK enzymatic assays, and conferred upon cells prodrug sensitivities equivalent to or better than that observed for each enzyme independently (ganciclovir [GCV] and bromovinyldeoxyuridine [BVdU] for HSV-1 TK and 5-fluorocytosine [5-FC] for CD). Simultaneous treatment of CDglyTK-expressing cells with prodrugs specific for HSV-1 TK and CD (GCV/5-FC or BVdU/5-FC) resulted in slight synergistic toxicity, two- to three-fold greater than that expected if the cytotoxic effects of each prodrug were purely additive. More importantly, co-treatment with HSV-1 TK- and CD-specific prodrugs was found to increase greatly the radiosensitivity of CDglyTK-expressing cells. Sensitivity enhancement ratios of 2.44 (GCV/5-FC) and 3.90 (BVdU/5-FC) were achieved. The results suggest that double suicide gene therapy, using a bifunctional CD/HSV-1 TK fusion gene, coupled with radiotherapy may provide a highly efficient means of selectively treating cancer.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Blotting, Western
  • Bromodeoxyuridine / analogs & derivatives
  • Bromodeoxyuridine / pharmacology
  • Bromodeoxyuridine / toxicity
  • Cytosine / metabolism
  • Cytosine Deaminase
  • Deoxyuridine / metabolism
  • Enzyme Inhibitors / pharmacology
  • Enzyme Inhibitors / toxicity
  • Escherichia coli / enzymology
  • Flucytosine / pharmacology
  • Flucytosine / toxicity
  • Ganciclovir / pharmacology
  • Ganciclovir / toxicity
  • Gene Expression Regulation, Viral / genetics*
  • Gene Transfer Techniques*
  • Genetic Therapy
  • Genetic Vectors / genetics
  • Gliosarcoma / metabolism*
  • Humans
  • Nucleoside Deaminases / genetics
  • Nucleoside Deaminases / metabolism
  • Prodrugs / pharmacology
  • Prodrugs / toxicity
  • Radiation Tolerance / physiology
  • Recombinant Fusion Proteins / genetics*
  • Recombinant Fusion Proteins / isolation & purification
  • Recombinant Fusion Proteins / metabolism
  • Simplexvirus / enzymology
  • Thymidine Kinase / genetics
  • Thymidine Kinase / metabolism
  • Tumor Cells, Cultured


  • Enzyme Inhibitors
  • Prodrugs
  • Recombinant Fusion Proteins
  • brivudine
  • Cytosine
  • Flucytosine
  • Thymidine Kinase
  • Nucleoside Deaminases
  • Cytosine Deaminase
  • Bromodeoxyuridine
  • Ganciclovir
  • Deoxyuridine