Improvement of antitumor activity by gene amplification with a replicating but nondisseminating adenovirus

Cancer Res. 2007 Apr 1;67(7):3387-95. doi: 10.1158/0008-5472.CAN-06-4317.


Gene therapy is a promising approach for cancer treatment; however, efficacy of current vectors remains insufficient. To improve the success of suicide gene therapy, we constructed a replication-competent adenoviral vector that has its protease gene deleted and expresses bacterial cytosine deaminase fused with bacterial uracil phosphoribosyltransferase (CU). The prodrug, 5-fluorocytosine, is transformed into the highly toxic and tissue-diffusible 5-fluorouracil by CU in infected cells. This vector is incapable of producing infectious particles but is able to undergo a single round of replication, thereby increasing transgene copy number and expression. In the presence of 5-FC, compared with the first-generation vector (AdCU), the replication-competent vector, Ad(dPS)CU-IRES-E1A, was significantly more efficacious for in vitro tumor cell killing and in bystander assays, whereas 25-fold fewer viral particles were required in a three-dimensional spheroid model. For in vivo experiments, in which virus was injected into preestablished intracranial glioma xenografts, followed by 5-FC treatment, mice receiving Ad(dPS)CU-IRES-E1A had significantly smaller tumors at 35 days postinjection as well as significantly longer median survival than mice treated with the replication-deficient, protease-deleted vector [Ad(dPS)CU]. In an immunocompetent syngeneic model, Ad(dPS)CU + 5-FC-treated mice had a median survival of only 23 days, whereas Ad(dPS)CU-IRES-E1A + 5-FC-treated animals had a survival of 57.1% at 365 days. In conclusion, Ad(dPS)CU-IRES-E1A in the presence of 5-FC produces more potent tumoricidal effects than its replication-deficient counterparts.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenoviridae / enzymology
  • Adenoviridae / genetics*
  • Adenoviridae / physiology
  • Animals
  • Cell Line, Tumor
  • Cytosine Deaminase / genetics
  • Cytosine Deaminase / metabolism
  • Flucytosine / pharmacokinetics
  • Fluorouracil / pharmacokinetics
  • Fluorouracil / pharmacology
  • Gene Amplification
  • Genetic Therapy / methods*
  • Genetic Vectors / genetics
  • Genome, Viral
  • Glioblastoma / genetics
  • Glioblastoma / therapy*
  • Humans
  • Mice
  • Mice, Inbred C57BL
  • Mice, Nude
  • Pentosyltransferases / genetics
  • Pentosyltransferases / metabolism
  • Peptide Hydrolases / deficiency*
  • Peptide Hydrolases / genetics
  • Spheroids, Cellular
  • Transgenes
  • Virus Replication


  • Flucytosine
  • Pentosyltransferases
  • uracil phosphoribosyltransferase
  • Peptide Hydrolases
  • Cytosine Deaminase
  • Fluorouracil