Azidothymidine in combination with 5-fluorouracil in human colorectal cell lines: In vitro synergistic cytotoxicity and DNA-induced strand-breaks

M. Andreuccetti, G. Allegrini, A. Antonuzzo, G. Malvaldi, P. F. Conte, R. Danesi, M. Del Tacca, A. Falcone

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

The in vitro cytotoxicity of the combination of azidothymidine (AZT) and 5-fluorouracil (5-FU) against the human colorectal cancer cells SW-480, SW- 620 and COLO-320DM was evaluated. The cytotoxic effects of 5-FU and AZT were determined by the assay using 2,3-bis(2-methoxy-4-nitro-5-sulfophenil)-2H- tetrazolium-5-carboxanilide inner salt (XXT), while drug-induced DNA strand- breaks were measured using a fluorometric analysis of DNA unwinding. After an exposure of 72 h, 5-FU and AZT induced a dose-dependent cytotoxicity against each cell line. The addition of 3, 10 and 30 μM AZT to various concentrations of 5-FU, as well as the addition of 0.5, 1 and 3 μm 5-FU to various concentrations of AZT, resulted in an enhanced cytotoxic effect. Isobologram analysis and the combination index (CI) method demonstrated that the interaction between 5-FU and AZT was clearly synergistic in each cell line, except for the 30% level of effect in SW-620, where borderline synergism was observed. The evaluation of DNA strand-breaks after an exposure of 16 h to 5-FU, AZT or 5-FU + AZT demonstrated that the 5-FU + AZT combination produced the greatest DNA damage, and that this interaction was synergistic in each cell fine. In conclusion, our study supports the evidence that the potential antitumour activity of AZT can be modulated by combining it with agents which inhibit thymidylate (dTMP) formation, such as 5-FU, and that the increased eytotoxicity is related to enhanced DNA damage. These findings should encourage further experimental and clinical studies of the potential use of AZT in combination with inhibitors of de novo dTMP synthesis.

Original languageEnglish
Pages (from-to)1219-1226
Number of pages8
JournalEuropean Journal of Cancer
Volume32
Issue number7
DOIs
Publication statusPublished - Jun 1996

Fingerprint

Zidovudine
Fluorouracil
Cell Line
DNA
DNA Breaks
DNA Damage
In Vitro Techniques
Fluorometry
Colorectal Neoplasms
Salts

Keywords

  • 5-fluorouracil
  • azidothymidine
  • colorectal cancer cell lines
  • DNA strand-breaks
  • synergistic cytotoxicity

ASJC Scopus subject areas

  • Cancer Research
  • Hematology
  • Oncology

Cite this

Azidothymidine in combination with 5-fluorouracil in human colorectal cell lines : In vitro synergistic cytotoxicity and DNA-induced strand-breaks. / Andreuccetti, M.; Allegrini, G.; Antonuzzo, A.; Malvaldi, G.; Conte, P. F.; Danesi, R.; Del Tacca, M.; Falcone, A.

In: European Journal of Cancer, Vol. 32, No. 7, 06.1996, p. 1219-1226.

Research output: Contribution to journalArticle

Andreuccetti, M. ; Allegrini, G. ; Antonuzzo, A. ; Malvaldi, G. ; Conte, P. F. ; Danesi, R. ; Del Tacca, M. ; Falcone, A. / Azidothymidine in combination with 5-fluorouracil in human colorectal cell lines : In vitro synergistic cytotoxicity and DNA-induced strand-breaks. In: European Journal of Cancer. 1996 ; Vol. 32, No. 7. pp. 1219-1226.
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abstract = "The in vitro cytotoxicity of the combination of azidothymidine (AZT) and 5-fluorouracil (5-FU) against the human colorectal cancer cells SW-480, SW- 620 and COLO-320DM was evaluated. The cytotoxic effects of 5-FU and AZT were determined by the assay using 2,3-bis(2-methoxy-4-nitro-5-sulfophenil)-2H- tetrazolium-5-carboxanilide inner salt (XXT), while drug-induced DNA strand- breaks were measured using a fluorometric analysis of DNA unwinding. After an exposure of 72 h, 5-FU and AZT induced a dose-dependent cytotoxicity against each cell line. The addition of 3, 10 and 30 μM AZT to various concentrations of 5-FU, as well as the addition of 0.5, 1 and 3 μm 5-FU to various concentrations of AZT, resulted in an enhanced cytotoxic effect. Isobologram analysis and the combination index (CI) method demonstrated that the interaction between 5-FU and AZT was clearly synergistic in each cell line, except for the 30{\%} level of effect in SW-620, where borderline synergism was observed. The evaluation of DNA strand-breaks after an exposure of 16 h to 5-FU, AZT or 5-FU + AZT demonstrated that the 5-FU + AZT combination produced the greatest DNA damage, and that this interaction was synergistic in each cell fine. In conclusion, our study supports the evidence that the potential antitumour activity of AZT can be modulated by combining it with agents which inhibit thymidylate (dTMP) formation, such as 5-FU, and that the increased eytotoxicity is related to enhanced DNA damage. These findings should encourage further experimental and clinical studies of the potential use of AZT in combination with inhibitors of de novo dTMP synthesis.",
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