Transduction of thymidine phosphorylase cDNA facilitates efficacy of cytosine deaminase/5-FC gene therapy for malignant brain tumor

Anticancer Res. Jul-Aug 2001;21(4A):2265-72.


The in vivo gene delivery of E. coli cytosine deaminase (cd) cDNA and systemic 5-fluorocytosine (5-FC) administration have been studied extensively because of their clinical relevance to cancer gene therapy. This approach has the potent advantage of a stronger bystander effect compared to the previous thymidine kinase suicide gene system of the herpes simplex virus. However, 5-fluorouracil (5-FU), an active metabolite in cd with 5-FC therapy, is not always effective for every type of tumor since the enzymes responsible for further drug metabolism vary significantly in each tissue. In this study, we aimed to increase the sensitivity of 5-FU by transduction of thymidine phosphorylase (dThdPase) cDNA into brain tumor cells. After retroviral transfer of the cDNA, we obtained 9L murine gliosarcoma cells showing stable expression of the target enzyme (9L-dThdPase). The growth of the cells was identical to wild type (9L-WT) or control-vector transfected (9L-Neo) cells in vitro. Sensitivity to 5-FU was increased in 9L-dThdPase cells. After the adenoviral delivery of cytosine deaminase gene into these cells, 9L-dThdPase cells also demonstrated an increased sensitivity to 5-FC. Moreover, we showed that transduction of dThdPase cDNA prolongs the survival of animals bearing intracerebral tumors after experimental in vivo cytosine deaminase gene therapy. These results suggest that transduction of thymidine phosphorylase may be a beneficial approach to increasing the efficacy of cd/5-FC suicide gene therapy in certain types of tumor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenoviridae / genetics
  • Animals
  • Antimetabolites, Antineoplastic / pharmacokinetics
  • Antimetabolites, Antineoplastic / pharmacology*
  • Brain Neoplasms / enzymology
  • Brain Neoplasms / genetics
  • Brain Neoplasms / therapy*
  • Cytosine Deaminase
  • DNA, Complementary / administration & dosage
  • DNA, Complementary / genetics*
  • Flucytosine / pharmacokinetics
  • Flucytosine / pharmacology*
  • Fluorouracil / pharmacokinetics
  • Fluorouracil / pharmacology
  • Genetic Therapy / methods*
  • Genetic Vectors / genetics
  • Gliosarcoma / enzymology
  • Gliosarcoma / genetics
  • Gliosarcoma / therapy*
  • Male
  • Nucleoside Deaminases / genetics*
  • Nucleoside Deaminases / metabolism
  • Rats
  • Rats, Inbred F344
  • Thymidine Kinase / genetics
  • Thymidine Kinase / metabolism
  • Thymidine Phosphorylase / biosynthesis
  • Thymidine Phosphorylase / genetics*
  • Thymidine Phosphorylase / metabolism
  • Transduction, Genetic


  • Antimetabolites, Antineoplastic
  • DNA, Complementary
  • Flucytosine
  • Thymidine Phosphorylase
  • Thymidine Kinase
  • Nucleoside Deaminases
  • Cytosine Deaminase
  • Fluorouracil