Low folate conditions may enhance the interaction of trifluorothymidine with antifolates in colon cancer cells
- 12 July 2005
- journal article
- research article
- Published by Springer Science and Business Media LLC in Cancer Chemotherapy and Pharmacology
- Vol. 57 (2), 171-179
- https://doi.org/10.1007/s00280-005-0033-4
Abstract
Purpose: Trifluorothymidine (TFT) is a fluoropyrimidine that is part of the novel combination metabolite TAS-102, in which TFT is combined with a potent thymidine phosphorylase inhibitor (TPI). TAS-102 is currently tested as an orally chemotherapeutic agent in different schedules in a phase I study. In its monophosphate form, TFT can inhibit thymidylate synthase (TS) activity after binding to the TS-nucleotide binding site leading to dTTP depletion, and in its triphosphate form TFT is incorporated into DNA, eventually leading to DNA damage. In this in vitro study, we investigated whether TFT could potentiate cytotoxicity of the antifolate-based TS inhibitors AG337 (Nolatrexed), ZD1694 (Raltitrexed) and GW1843; and whether increased TS inhibition or DNA damage would be related to this result. Methods: The drug combinations were studied in colon cancer cell lines either grown at low or high folate conditions. Multiple drug effect analysis was performed after measuring growth inhibition when the drugs were combined (MTT Assay) and expressed as Combination Index (CI), where CI1.1 indicates antagonism. Drug target analysis was performed using the TS in situ inhibition assay and the FADU DNA-damage assay. Cells were exposed to either the drugs alone or in combination to determine the effect on TS activity and DNA damage induction, respectively. Results: Three experimental procedures were used to test the interaction of the drugs: either one of the drugs was kept at a constant concentration (IC25) or two drugs were added in a 1:1 IC50-based molar ratio. The combinations of TFT with one of the antifolates in which one of the drugs was kept at a constant concentration were synergistic for all antifolates in WiDr/F cells, which grow in low folate medium (CI=0.6–0.8), but only additive to antagonistic for the cell lines growing in high folate medium: TFT-AG337: CI=0.9–2.3; TFT-ZD1694: CI=0.9–1.3; TFT-GW1843: CI=0.8–1.7. The procedure in which the two drugs were added in a 1:1 IC50-based molar ratio showed antagonism for all three combinations in all cell lines (CI>2.7). TS inhibition (14.3%) and DNA damage (8%) were more pronounced than expected (PConclusions: The combination of TFT with the antifolates AG337, ZD1694 and GW1843 is mainly additive when the drugs are given simultaneously and this is mediated by an additive TS inhibition and DNA damage. The drug interaction may partly be dependent on the folate homeostasis since WiDr/F cells growing at low folate conditions show pronounced synergism in growth inhibition, two-sided TS inhibition and DNA damage, especially when TFT is combined with the tight-binding TS inhibitor GW1843.Keywords
This publication has 34 references indexed in Scilit:
- Intracellular Thymidylate Synthase Inhibition by Trifluorothymidine in FM3A CellsNucleosides, Nucleotides and Nucleic Acids, 2004
- FDA Drug Approval Summaries: Pemetrexed (Alimta®)The Oncologist, 2004
- Pharmacokinetics, Safety, and Efficacy of a Liposome Encapsulated Thymidylate Synthase Inhibitor, OSI-7904L [(S)-2-[5-[(1,2-Dihydro-3-methyl-1-oxobenzo[f]quinazolin-9-yl)methyl]amino-1-oxo-2-isoindolynl]-glutaric Acid] in MiceJournal of Pharmacology and Experimental Therapeutics, 2004
- Biochemical mechanisms of interferon modulation of 5-fluorouracil activity in colon cancer cellsEuropean Journal Of Cancer, 1997
- Folate-based thymidylate synthase inhibitors in cancer chemotherapyAnti-Cancer Drugs, 1997
- THE CATALYTIC MECHANISM AND STRUCTURE OF THYMIDYLATE SYNTHASEAnnual Review of Biochemistry, 1995
- Mechanism-Based Inhibition of Thymidylate Synthase by 5-(Trifluoromethyl)-2'-deoxyuridine 5'-MonophosphateBiochemistry, 1994
- Comparison of the sulforhodamine B protein and tetrazolium (MTT) assays for in vitro chemosensitivity testingEuropean Journal of Cancer and Clinical Oncology, 1991
- Irreversible inhibition of thymidylate synthetase by 5-formyl-2′-deoxyuridylic acidBiochemical and Biophysical Research Communications, 1972
- Thymidylate synthetase. Model studies of inhibition by 5-trifluoromethyl-2'-deoxyuridylic acidBiochemistry, 1971