Enzyme/prodrug gene therapy for human colon cancer cells using adenovirus-mediated transfer of the Escherichia coli cytosine deaminase gene driven by a CAG promoter associated with 5-fluorocytosine administration

J Exp Clin Cancer Res. 2000 Mar;19(1):75-80.


Escherichia coli cytosine deaminase (CD), which is a prokaryotic enzyme, converts nontoxic prodrug 5-fluorocytosine (5-FC) into the toxic chemotherapeutic agent 5-fluorouracil (5-FU). To investigate an enzyme/prodrug gene therapy for colorectal cancer, using adenoviral gene transfer of the E. coli CD gene associated with administration of 5-FC, we constructed replication-defective adenovirus vectors expressing the E. coli CD gene or lacZ gene driven by a CAG promoter (composed of a cytomegalovirus immediate early enhancer and a chicken beta-actin promotor). The present study demonstrated that an adenoviral gene transfer system using a CAG promoter induced sufficient gene expression of CD to confer the cytotoxicity of 5-FC to HT29 human colon cancer cells by converting it into 5-FU even at an moi of one. Furthermore, experimental gene therapy using intratumoral injection of the CD-expressing adenovirus with systemical administration of 5'-FC successfully suppressed the growth of established HT29 subcutaneous tumors in nude mice. These results suggest that enzyme/prodrug gene therapy using the adenoviral gene transfer of the E. coli CD gene with concomitant administration of 5-FC may be an effective strategy in the local control of colorectal cancer.

MeSH terms

  • Adenoviridae
  • Animals
  • Colonic Neoplasms / genetics*
  • Colonic Neoplasms / therapy*
  • Cytosine Deaminase
  • Escherichia coli / genetics
  • Flucytosine / therapeutic use*
  • Gene Transfer Techniques*
  • Genetic Therapy*
  • Genetic Vectors*
  • Humans
  • Mice
  • Nucleoside Deaminases / genetics*
  • Nucleoside Deaminases / therapeutic use*
  • Prodrugs / therapeutic use*
  • Promoter Regions, Genetic
  • Tumor Cells, Cultured


  • Prodrugs
  • Flucytosine
  • Nucleoside Deaminases
  • Cytosine Deaminase