Enhancement of 5-fluorouracil cytotoxicity by human thymidine-phosphorylase expression in cancer cells: in vitro and in vivo study

Int J Cancer. 1999 Jan 29;80(3):465-70. doi: 10.1002/(sici)1097-0215(19990129)80:3<465::aid-ijc21>3.0.co;2-6.


Transferring a gene into cancer cells in order to sensitize them to drugs is an important approach in human cancer gene-therapy research. Thymidine phosphorylase (TP) is the first enzyme in the metabolic activation pathway of 5-fluorouracil (5-FU) to fluorodeoxyribonucleotides, thus, it could be used to increase the sensitivity of cancer cells to this anti-pyrimidine agent. In this study, an expression vector containing the human TP cDNA was transfected into C26 murine colon-carcinoma cells. Stable transfectants were selected; all showed increased TP activity, ranging from 2- to 10-fold when compared with wild-type cells. The in vitro sensitivity of transfectants to 5-FU and 5'-deoxy-5-fluorouridine (5'-DFUR) was enhanced, in agreement with the observed increase in TP activity. Then, tumors were generated by s.c. injection of TP-transfected or wild-type C26 cells in syngeneic BALB/c mice. 5-FU (25 mg/kg, i.p.) induced a growth delay of TP-transfected C26 tumors as compared with C26 wild-type tumors. These data suggest that TP could be transfected in tumor cells to increase the sensitivity to 5-FU for subsequent cancer gene therapy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antimetabolites, Antineoplastic / pharmacology*
  • Carcinoma / drug therapy
  • Carcinoma / genetics
  • Carcinoma / therapy
  • Colonic Neoplasms / drug therapy
  • Colonic Neoplasms / genetics
  • Colonic Neoplasms / therapy
  • Drug Synergism
  • Floxuridine / metabolism
  • Floxuridine / pharmacology
  • Fluorouracil / pharmacology*
  • Humans
  • Mice
  • Mice, Inbred BALB C
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism*
  • Thymidine Phosphorylase / genetics
  • Thymidine Phosphorylase / metabolism*
  • Transfection


  • Antimetabolites, Antineoplastic
  • Neoplasm Proteins
  • Floxuridine
  • Thymidine Phosphorylase
  • Fluorouracil
  • doxifluridine