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ORIGINAL RESEARCH article

Front. Pharmacol.
Sec. Drug Metabolism and Transport
Volume 15 - 2024 | doi: 10.3389/fphar.2024.1450418
This article is part of the Research Topic Drug Metabolism and Transport: The Frontier of Personalized Medicine Volume II View all 10 articles

The role of l-leucovorin uptake and metabolism in the modulation of 5-fluorouracil efficacy and antifolate toxicity

Provisionally accepted
Godefridus J. Peters Godefridus J. Peters 1,2*Ietje Kathmann Ietje Kathmann 3Elisa Giovannetti Elisa Giovannetti 3Kees Smid Kees Smid 3Yehuda G. Assaraf Yehuda G. Assaraf 4Gerrit Jansen Gerrit Jansen 3
  • 1 Oncology, Amsterdam University Medical Centers, Amsterdam, Netherlands
  • 2 VU Amsterdam, Amsterdam, Netherlands, Netherlands
  • 3 Amsterdam University Medical Centers, Amsterdam, Netherlands
  • 4 Technion Israel Institute of Technology, Haifa, Haifa, Israel

The final, formatted version of the article will be published soon.

    Background: L-Leucovorin (l-LV; 5-formyltetrahydrofolate, folinic acid) is a precursor for 5,10methylenetetrahydrofolate (5,10-CH2-THF), which is important in the potentiation of the antitumor activity of 5-fluorouracil (5FU). LV is also used to rescue antifolate toxicity. LV is commonly administered as a racemic mixture of its l-LV and d-LV stereoisomers. We compared dl-LV with l-LV and investigated whether d-LV would interfere with the activity of l-LV.Methods: Using radioactive substrates, we characterized the transport properties of l-LV and d-LV, and compared the efficacy of l-LV with d-LV to potentiate 5FU-mediated thymidylate synthase (TS) inhibition. Using proliferation assays we investigated their potential to protect cancer cells from cytotoxicity of the antifolates methotrexate, pemetrexed (Alimta), raltitrexed (Tomudex) and pralatrexate.Results: l-LV displayed an 8-fold and 3.5-fold higher substrate affinity than d-LV for the reduced folate carrier (RFC/SLC19A1) and proton coupled folate transporter (PCFT/SLC46A1), respectively. In selected colon cancer cell lines, the greatest enhanced efficacy of 5FU was observed for l-LV (2-fold) followed by the racemic mixture, whereas d-LV was ineffective. The cytotoxicity of antifolates in lymphoma and various solid tumor cell lines could be protected very efficiently by l-LV but not by d-LV. This protective effect of l-LV was dependent on cellular RFC expression as corroborated in RFC/PCFT-knockout and RFC/PCFT-transfected cells.Assessment of TS activity in situ showed that TS inhibition by 5FU could be enhanced by l-LV and dl-LV and only partially by d-LV. However, protection from inhibition by various antifolates was solely achieved by l-LV and dl-LV.In conclusion, in general l-LV acts similar to the dl-LV formulations, however disparate effects were observed when d-LV and l-LV were used in combination, conceivably by d-LV affecting (anti)folate transport and intracellular metabolism.

    Keywords: leucovorin stereo-isomers, L-leucovorin, Thymidylate Synthase, 5-fluorouracil, Antifolates, pemetrexed

    Received: 17 Jun 2024; Accepted: 30 Jul 2024.

    Copyright: © 2024 Peters, Kathmann, Giovannetti, Smid, Assaraf and Jansen. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Godefridus J. Peters, Oncology, Amsterdam University Medical Centers, Amsterdam, Netherlands

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