A Structurally Altered Human Reduced Folate Carrier with Increased Folic Acid Transport Mediates a Novel Mechanism of Antifolate Resistance

Jansen, Gerrit; Mauritz, R.; Drori, Stavit; Sprecher, Hannah; Kathmann, Ietje; Bunni, Marlene A.; Priest, David G.; Noordhuis, Paul; Schornagel, J. H.; Pinedo, H.M.; Peters, Godefridus J.; Assaraf, Yehuda G.

doi:10.1074/jbc.273.46.30189

Cited by 142 publications

(158 citation statements)

References 55 publications

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“…First, the efficacy of MTX was progressively reduced when it was combined with increasing concentrations of SSZ. In fact, the levels of loss of MTX efficacy at high concentrations of SSZ (Ͼ400-fold in the presence of 2.5 mM SSZ) were similar to those demonstrated in cells displaying loss of MTX efficacy due to decreased expression of the RFC protein (28,38,39,56). In this respect, the decreased expression of RFC (up to 8-fold) in CEM/SSZ cells (Figure 4) also could have contributed to a diminished efficacy of MTX, but data shown in Figures 1A and B did not reveal a difference between the MTX efficacy in CEM/SSZ cells and that in CEM cells.…”

Section: Discussionsupporting

confidence: 60%

“…SSZ-induced cellular folate deficiency is also reflected by hypersensitivity to the folate antagonist trimetrexate. Hypersensitivity to trimetrexate has been described in cells with low intracellular folate levels due to quantitatively and/or qualitatively defective RFC protein (38,39,57,58). Here we demonstrate that direct inhibition of RFC function by SSZ can confer the same phenotype of increased sensitivity for the folate antagonist trimetrexate.…”

Section: Discussionmentioning

confidence: 99%

“…Given their anionic nature, natural folates and MTX cannot traverse the plasma membrane; therefore, RFC-mediated cellular uptake should be regarded as the first critical step in any antiinflammatory/antiproliferative mode of action of MTX (33)(34)(35)(36). Consequently, diminished transport activity of RFC has been associated with loss of MTX efficacy and with folate deficiency (31,(37)(38)(39)(40).…”

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confidence: 99%

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Sulfasalazine is a potent inhibitor of the reduced folate carrier: Implications for combination therapies with methotrexate in rheumatoid arthritis

Jansen¹,

Heijden²,

Oerlemans³

et al. 2004

Arthritis & Rheumatism

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Objective. To investigate whether interactions of sulfasalazine (SSZ) with reduced folate carrier (RFC), the dominant cell membrane transporter for natural folates and methotrexate (MTX), may limit the efficacy of combination therapy with MTX and SSZ in patients with rheumatoid arthritis. Conclusion. At clinically relevant plasma concentrations, interactions of SSZ with RFC provide a biochemical rationale for 2 important clinical observations: 1) the onset of (sub)clinical folate deficiency during SSZ treatment, and 2) the lack of additivity/synergism of the combination of SSZ and MTX when these diseasemodifying antirheumatic drugs are administered simultaneously. Thus, when considering use of these drugs in combination therapies, the present results provide a rationale both for the use of folate supplementation and for spacing administration of these drugs over time.

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Section: Discussionsupporting

confidence: 60%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Sulfasalazine is a potent inhibitor of the reduced folate carrier: Implications for combination therapies with methotrexate in rheumatoid arthritis

Jansen¹,

Heijden²,

Oerlemans³

et al. 2004

Arthritis & Rheumatism

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“…Expression of the RFC/SLC19A1 gene was down-regulated more than 2-fold in the MTXresistant cells, thereby confirming the role of this influx transporter as an important determinant of antifolate resistance [18][19][20][21] . However, the major finding of the present investigation is that the dramatic loss of FPGS activity in the 7-OHMTX cells, presumably associated with decreased intracellular levels of folate, was accompanied by consistent alterations in the expression of genes capable of preserving intracellular pools of reduced folate and/or increase purine nucleotide biosynthesis.…”

Section: Corroboration Of Array Expression Levels By Qrt-pcrmentioning

confidence: 60%

Gene expression profiling of leukemia T-cells resistant to methotrexate and 7-hydroxymethotrexate reveals alterations that preserve intracellular levels of folate and nucleotide biosynthesis

Fotoohi¹,

Assaraf²,

Moshfegh³

et al. 2009

Biochemical Pharmacology

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International audiencetreatment of human T-cell leukemia cells with 7-hydroxymethotrexate, the major metabolite of methotrexate resulted in acquired resistance as a result of the complete loss of folypolyglutamate synthetase (FPGS) activity. This was in contradistinction to the major modality of antifolate resistance of impaired drug transport in leukemia cells exposed to methotrexate.. To identify the genes associated with methotrexate and 7-hydroxymethotrexate resistance, we herein explored the patterns of genome-wide expression profiles in these antifolte-resistant leukemia sublines. mRNA levels of the reduced folate carrier, the primary influx transporter of folates and antifolates, were down-regulated >2-fold in methotrexate -resistant cells. The dramatic loss of FPGS activity in 7-hydroxymethotrexate - resistant cells was associated with alterations in the expression of various genes aimed at preserving reduced folates and/or enhancing purine nucleotide biosynthesis e.g. methylene tetrahydrofolate reductase, glycinamide ribonucleotide formyltransferase, adenosine deaminase, cystathionine β synthase, as well as the ATP-dependent folate exporters / and /. The observed changes in gene expression were generally not paralleled by acquired DNA copy numbers alterations, suggesting transcriptional regulatory mechanisms. Interestingly, gene expression of DNA/RNA metabolism and transport genes were more profoundly altered in methotrexate -resistant subline, whereas in 7-hydroxymethotrexate -resistant cells, the most profoundly affected groups of genes were those encoding for proteins involved in metabolism and cellular proliferation. Thus, the present investigation provides evidence that 7-hydroxymethotrexate induces gene expression alterations and an antifolate resistance modality that are distinct from its parent drug methotrexate

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“…This is in accordance with a study by Sirotnak et al [57] with L1210-RFC cells in another mouse strain. Our data show that dietary folate depletion could further enhance the anti-leukaemic eVect of both drugs, most likely due to less competition for cellular uptake and polyglutamylation by circulating plasma folates [27]. In contrast to L1210-RFC cells, MTX and EDX did not evoke a substantial antileukaemic eVect against L1210-MFR cells.…”

Section: Discussionmentioning

confidence: 70%

Dynamics of antifolate transport via the reduced folate carrier and the membrane folate receptor in murine leukaemia cells in vitro and in vivo

Mauritz

Peters

Kathmann

et al. 2008

Cancer Chemother Pharmacol

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Murine L1210 leukaemia cells expressing either the reduced folate carrier (RFC) or the membrane folate receptor (MFR) were studied in vitro and in vivo to assess the dynamics of membrane transport of two categories antifolates; folate-based inhibitors of dihydrofolate reductase (methotrexate, edatrexate, aminopterin, PT523, and PT644) and thymidylate synthase (TS) [CB3717, raltitrexed, plevitrexed (BGC9331), pemetrexed and GW1843]. The potency of in situ inhibition of TS was used as an endpoint to analyze the in vitro dynamics of RFC/ MFR-membrane transport of these antifolates. Both for L1210-RFC and L1210-MFR cells, the potency of in situ TS inhibition was closely correlated with increasing aYnities of these transporters for the antifolates (r = 0.64, P < 0.05 and r = ¡0.65, P < 0.05, respectively). Within the group of antifolates for which MFR had a low binding aYnity, those that had the ability to become polyglutamylated, were more potent inhibitors of TS in situ activity than non-polyglutamatable antifolates. In vivo activity of methotrexate, edatrexate, raltitrexed and pemetrexed was assessed in L1210-RFC and L1210-MFR bearing mice that were fed either a standard or a folate-deWcient chow. Dietary folate depletion signiWcantly reduced the MTD for methotrexate (sevenfold), edatrexate (sevenfold), raltitrexed (50-fold) and pemetrexed (150-fold). Based on increased life spans, antitumor eVects of methotrexate and edatrexate were markedly better in L1210-RFC bearing mice on the folate-deWcient chow (ILS: 455 and 544%, respectively) than on standard chow (ILS: 213 and 263%, respectively). No therapeutic eVects of methotrexate and edatrexate were observed for L1210-MFR bearing mice on either chow condition, which may be consistent with the low binding aYnity for MFR. Irrespective of the folate diet status, pemetrexed and raltitrexed were inactive against both L1210-RFC and L1210-MFR bearing mice, which may be due to high circulating plasma thymidine levels. Collectively, this study underscores that modulation of dietary folate status can provide a basis within which the therapeutic eVect of antifolates may be further improved.

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A Structurally Altered Human Reduced Folate Carrier with Increased Folic Acid Transport Mediates a Novel Mechanism of Antifolate Resistance

Cited by 142 publications

References 55 publications

Sulfasalazine is a potent inhibitor of the reduced folate carrier: Implications for combination therapies with methotrexate in rheumatoid arthritis

Sulfasalazine is a potent inhibitor of the reduced folate carrier: Implications for combination therapies with methotrexate in rheumatoid arthritis

Gene expression profiling of leukemia T-cells resistant to methotrexate and 7-hydroxymethotrexate reveals alterations that preserve intracellular levels of folate and nucleotide biosynthesis

Dynamics of antifolate transport via the reduced folate carrier and the membrane folate receptor in murine leukaemia cells in vitro and in vivo

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