Preservation of folate transport activity with a low-pH optimum in rat IEC-6 intestinal epithelial cell lines that lack reduced folate carrier function

Wang, Yanhua; Rajgopal, Arun; Goldman, I. David; Zhao, Rongbao

doi:10.1152/ajpcell.00307.2004

Cited by 26 publications

(26 citation statements)

References 36 publications

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“…Uptake of pemetrexed at low pH was also assessed (data not shown). Transport at pH 5.5 was negligibly decreased (15% P = 0.053) consistent with other observations from this laboratory that this transport activity is almost entirely independent of RFC (15,17).…”

Section: A S Se S Sment Of Pemetrexed and 5 -Cho-thf Accumulation Undsupporting

confidence: 91%

“…Therefore, transport-mediated resistance would be expected to be restricted to loss of RFC function. This strategy has been used previously for developing RFC-null IEC-6 intestinal cells (17). The properties of an HCT-15 -derived clone (PT1) are described in which RFC was mutated, transport activity was lost, and there was only a very low level of residual pemetrexed influx activity.…”

Section: Introductionmentioning

confidence: 99%

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The inverse relationship between reduced folate carrier function and Pemetrexed activity in a human colon cancer cell line

Chattopadhyay

Zhao

Krupenko

et al. 2006

Molecular Cancer Therapeutics

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Pemetrexed, a new generation antifolate recently approved for the treatment of mesothelioma and non -small cell lung cancer, is an excellent substrate for the reduced folate carrier (RFC). To explore the carrier's effect on pemetrexed activity, RFC was inactivated in HCT-15 colon cancer cells by mutagenesis and PT632 selective pressure. A clone (PT1) was obtained with a glycine to arginine substitution at amino acid 401, resulting in the loss of RFC function. PT1 cells were resistant to PT632 (178-fold), methotrexate (4-fold), and ZD1694 (Tomudex, raltitrexed; 20-fold), but were 3-fold collaterally sensitive to pemetrexed when grown in 25 nmol/L of 5-formyltetrahydrofolate. PT1 cells transfected with wild-type RFC had antifolate sensitivities comparable to that of wild-type HCT-15 cells, indicating that the RFC mutation was the sole basis for resistance. Folate pools were contracted in PT1 cells by 32% or 60%, as measured by radiolabeling intracellular folates or by an enzyme binding assay, respectively. This was reflected in marked (6.5-fold) collateral sensitivity to trimetrexate. The initial uptake of pemetrexed in PT1 cells was markedly reduced (f85%) but intracellular pemetrexed levels increased to f60% and f70% to that of wild-type cells after 2 hours and 6 days, respectively. There was increased pemetrexed inhibition of glycinamide ribonucleotide transformylase and, to a lesser extent, thymidylate synthase in PT1 cells growing in 5-formyltetrahydrofolate based on nucleoside protection analyses. Hence, loss of RFC function leads to collateral sensitivity to pemetrexed in HCT-15 cells, likely due to cellular folate pool contraction resulting in partial preservation of pemetrexed polyglutamylation and increased target enzyme inhibition. [Mol Cancer Ther 2006;5(2):438 -49]

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Section: A S Se S Sment Of Pemetrexed and 5 -Cho-thf Accumulation Undsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

The inverse relationship between reduced folate carrier function and Pemetrexed activity in a human colon cancer cell line

Chattopadhyay

Zhao

Krupenko

et al. 2006

Molecular Cancer Therapeutics

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“…This transport activity was shown to be independent of RFC. Hence, low-pH activity persists in (a) HeLa cells in which there has been a genomic deletion of RFC (71), (b) HUH-7 hepatoma cells in which RFC is not expressed (72), and (c) HCT-15 colon cancer cells (73) and rat intestinal epithelial cells (IEC-6) in which the RFC is mutated and not functional (74). This activity was characterized in HeLa cells where influx of methotrexate at pH 5.5 exceeds transport at pH 7.4 by >5-fold (54).…”

Section: Folate Receptorsmentioning

confidence: 99%

Pemetrexed: biochemical and cellular pharmacology, mechanisms, and clinical applications

Chattopadhyay

Moran

Goldman

2007

Molecular Cancer Therapeutics

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Pemetrexed is a new-generation antifolate, approved for the treatment of mesothelioma and non -small cell lung cancer, currently being evaluated for the treatment of a variety of other solid tumors. This review traces the history of antifolates that led to the development of pemetrexed and describes the unique properties of this agent that distinguish it from other antifolates. These include (a) its very rapid conversion to active polyglutamate derivatives in cells that build to high levels and are retained for long intervals to achieve prolonged and potent inhibition of its major target enzyme thymidylate synthase, (b) its high affinity for three folate transporters, and (c) its marked sensitivity to the level of physiologic folates in cells. The latter results in the unique and paradoxical finding that when transport mediated by the major folate transporter (the reduced folate carrier) is impaired, pemetrexed activity is preserved. This is due to concurrent contraction of competing cellular physiologic folates and utilization of a novel second transport carrier for which pemetrexed has high affinity, recently identified as the proton-coupled folate transporter (PCFT). Laboratory studies are reviewed that raise the possibility of new approaches to the use of folic acid supplementation in clinical regimens with pemetrexed. [Mol Cancer Ther 2007;6(2):404 -17]

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“…Before the discovery of PCFT, RFC had long been regarded as the primary carrier-mediated intestinal folate transport protein (Chiao et al, 1997). However, RFCmediated transport has been characterized to be optimal at near-neutral pH, whereas intestinal folate transport activity functions optimally at acidic pH (Wang et al, 2005;Said and Seetharam, 2006). PCFT has high affinity for folates and operates optimally at low pH, and has recently been identified as the major molecular entity of the intestinal folate transport system (Qiu et al, 2006 andInoue et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Post-hatching ontogeny of intestinal proton-coupled folate transporter and reduced folate carrier in broiler chickens

Jing

Tactacan

House

2013

Animal

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Folate transporters, including the reduced folate carrier and the proton-coupled folate transporter, encoded by Slc19a1 and Slc46a1 genes respectively, play important roles in the transport of folate across biological membranes given the hydrophilic nature of folates. Although a number of studies have demonstrated that these two transporters are regulated ontogenetically in mammals, little data are available on their developmental patterns of expression in poultry. The objective of this study was to investigate the expression patterns of Slc19a1 and Slc46a1 in jejunal and cecal tissue of broiler chickens during post-hatching development. Post-hatch male chicks (Ross 3 Ross) had free access to water and a soybean/wheat-based diet. Jejunal, cecal and blood samples were collected on day-of-hatch but before feeding (D0), and on D2, D7, D14, D21 and D35 post-hatch (n 5 8 at each time point), respectively. Plasma folate concentrations were low on the day of hatch and increased with maturation; by contrast, plasma homocysteine, a marker of folate status, was highest (P , 0.05) in the day-of-hatch birds and decreased thereafter. Increasing age reduced mRNA abundance of Slc19a1 (P , 0.05) in the jejunum and cecum. Abundance of Slc46a1 mRNA (P , 0.05) gradually decreased in the cecum with increasing age and that of Slc46a1 in the jejunum initially decreased and then increased to level similar to that of day-of-hatch. The study provides some initial data on ontogenetic regulation of Slc19a1 and Slc46a1 in the jejunum and cecum of the chicken and lays the ground work for future nutritional studies. Moreover, the expression of Slc19a1 and Slc46a1 transcripts in the cecum provides evidence of the potential for cecally derived folate to contribute to the folate status of the host.

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Preservation of folate transport activity with a low-pH optimum in rat IEC-6 intestinal epithelial cell lines that lack reduced folate carrier function

Cited by 26 publications

References 36 publications

The inverse relationship between reduced folate carrier function and Pemetrexed activity in a human colon cancer cell line

The inverse relationship between reduced folate carrier function and Pemetrexed activity in a human colon cancer cell line

Pemetrexed: biochemical and cellular pharmacology, mechanisms, and clinical applications

Post-hatching ontogeny of intestinal proton-coupled folate transporter and reduced folate carrier in broiler chickens

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