Cancer Chemotherapy and Pharmacology

, Volume 56, Issue 3, pp 322–327

Effects and interaction of 7-hydroxy methotrexate and methotrexate in leukaemic cells ex vivo measured by the thymidylate synthase inhibition assay

  • R. M. Lingg
  • G. Hempel
  • M. G. Rots
  • C. H. Van Zantwijk
  • J. Boos
  • G. J. L. Kaspers
Short Communication

DOI: 10.1007/s00280-005-1032-1

Cite this article as:
Lingg, R.M., Hempel, G., Rots, .G. et al. Cancer Chemother Pharmacol (2005) 56: 322. doi:10.1007/s00280-005-1032-1

Abstract

In high dose therapy with methotrexate (MTX) the main metabolite 7-hydroxy-methotrexate (7-OH MTX) exceeds the plasma concentration of MTX achieving about tenfold higher levels. To investigate the interaction between 7-OH MTX and MTX ex vivo, the thymidylate synthase inhibition assay was used to quantify antifolate effects in patient blast samples, measuring the inhibition of the key enzyme thymidylate synthase (TS). In 18 leukemic samples (7 ALL, 11 AML) no dose-dependent TS inhibition was observed for 7-OH MTX. However, a statistically significant increase of TS inhibition (p<0.05) was observed for a 1:1 mixture of MTX and 7-OH MTX as compared to the effect of MTX alone. The half-maximal inhibitory concentrations in the short-exposure assay were 0.857 μM for MTX alone versus 0.088 μM for the 1:1 mixture with 7-OH MTX, respectively (p≤0.05). This interaction was not observed with an excess of 7-OH MTX. Similar results were obtained in long exposure experiments. We conclude that there is a dose-dependent interaction between 7-OHMTX and MTX, despite the lack of TS inhibitory effects of the metabolite alone.

Keywords

7-OH methotrexate Methotrexate Acute leukaemia Thymidylate synthase inhibition assay Interaction 

Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • R. M. Lingg
    • 1
  • G. Hempel
    • 1
    • 3
  • M. G. Rots
    • 2
  • C. H. Van Zantwijk
    • 2
  • J. Boos
    • 1
  • G. J. L. Kaspers
    • 2
  1. 1.Klinik und Poliklinik für Kinder- und Jugendmedizin, Pädiatrische Hämatologie/Onkologie Universitätsklinikum MünsterMünsterGermany
  2. 2.Department of Pediatric Hematology/OncologyVU university medical centerAmsterdamThe Netherlands
  3. 3.Institut für Pharmazeutische und Medizinische ChemieUniversity of MünsterMuensterGermany

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