The Role of Thymidylate Synthase Induction in Modulating p53-regulated Gene Expression in Response to 5-Fluorouracil and Antifolates

Daniel B Longley, John Boyer, Wendy L Allen, Tariq Latif, Paul R Ferguson, Pamela J Maxwell, Ultan McDermott, Maria Lynch, D Paul Harkin, Patrick G Johnston

Research output: Contribution to journalArticlepeer-review

89 Citations (Scopus)

Abstract

Thymidylate synthase (TS) is a critical target for chemotherapeutic agents such as 5-fluorouracil (5-FU) and antifolates such as tomudex (TDX),multitargeted antifolate, and ZD9331. Using the MCF-7 breast cancer line, we have developed p53 wild-type (M7TS90) and null (M7TS90-E6) isogenic lines with inducible TS expression (approximately 6-fold induction compared with control after 48 h). In the M7TS90 line, inducible TS expression resulted in a moderate approximately 3-fold increase in 5-FU IC-50(72 h) dose and a dramatic >20-fold increase in the IC-50(72 h) doses of TDX, multitargeted antifolate, and ZD9331. S-phase cell cycle arrest and apoptosis induced by the antifolates were abrogated by TS induction. In contrast, cell cycle arrest and apoptosis induced by 5-FU was unaffected by TS expression levels. Inactivation of p53 significantly increased resistance to 5-FU and the antifolates with IC-50(72 h) doses for 5-FU and TDX of >100 and >10 microM, respectively, in the M7TS90-E6 cell line. Furthermore, p53 inactivation completely abrogated the cell cycle arrest and apoptosis induced by 5-FU. The antifolates induced S-phase arrest in the p53 null cell line; however, the induction of apoptosis by these agents was significantly reduced compared with p53 wild-type cells. Both inducible TS expression and the addition of exogenous thymidine (10 microM) blocked p53 and p21 induction by the antifolates but not by 5-FU in the M7TS90 cell line. Similarly, inducible TS expression and exogenous thymidine abrogated antifolate but not 5-FU-mediated up-regulation of Fas/CD95 in M7TS90 cells. Our results indicate that in M7TS90 cells, inducible TS expression modulates p53 and p53 target gene expression in response to TS-targeted antifolate therapies but not to 5-FU.

Original languageEnglish
Pages (from-to)2644-2649
Number of pages6
JournalCancer Research
Volume62
Issue number9
Publication statusPublished - 2002

Keywords

  • Antigens, CD95
  • Breast Neoplasms
  • Cell Cycle
  • Enzyme Induction
  • Fluorouracil
  • Folic Acid Antagonists
  • Gene Expression Regulation, Enzymologic
  • Gene Expression Regulation, Neoplastic
  • Genes, p53
  • Humans
  • Thymidylate Synthase
  • Tumor Cells, Cultured
  • Tumor Suppressor Protein p53
  • Up-Regulation

ASJC Scopus subject areas

  • Cancer Research
  • Oncology

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