Differential usage of the transport systems for folic acid and methotrexate in normal human T-lymphocytes and leukemic cells.
Methotrexate (MTX) has been used as an effective anti-cancer drug for a long time. Conceptually, it is accepted that MTX and folic acid are transported by folate receptors (FRs) in cancerous cells, but the exact mechanism of MTX uptake in human leukemia is unknown. The objective of this study was to investigate different transport systems for FA and MTX, and to delineate their uptake mechanism in MOLT4, K562, Hut78 leukemia cells and normal human T cells. In MOLT4, uptake of MTX was higher than FA, similar to that of K562, Hut78 and normal T cells. In MOLT4 cells, MTX uptake was maximum at pH 7.4 whereas FA uptake was maximum at pH 4.5. Uptake of FA and MTX was significantly inhibited by anions, suggesting anion-dependent transport system. FA uptake was found to be energy dependent whereas MTX uptake was energy independent. RT-PCR and immunofluorescence results demonstrated the presence of reduced folate carrier as well as proton coupled folate transporter and absence of FR in MOLT4 and normal T cells. These data suggest the existence of two separate and independent carrier-mediated transport systems for the uptake of FA and MTX in normal and leukemic human T cells.
Biswal
Bijesh Kumar
BK
Stem Cell and Molecular Biology Laboratory, Department of Biotechnology, Indian Institute of Technology Madras, Chennai-600036, India.
Verma
Rama Shanker
RS
D000906:Antibodies / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002021:Buffers; D002352:Carrier Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D045744:Cell Line, Tumor; D058973:Folate Receptors, GPI-Anchored; D005492:Folic Acid / Q000031:analogs & derivatives / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007150:Immunohistochemistry; D007477:Ions; D007938:Leukemia / Q000378:metabolism* / Q000473:pathology*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008727:Methotrexate / Q000031:analogs & derivatives / Q000378:metabolism*; D016685:Mitomycin / Q000494:pharmacology; D010710:Phosphates / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D058978:Reduced Folate Carrier Protein; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012460:Sulfasalazine / Q000494:pharmacology; D013431:Sulfates / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors; D014700:Verapamil / Q000494:pharmacology
D000906:Antibodies; D002021:Buffers; D002352:Carrier Proteins; D058973:Folate Receptors, GPI-Anchored; D007477:Ions; D026901:Membrane Transport Proteins; D010710:Phosphates; D011956:Receptors, Cell Surface; D058978:Reduced Folate Carrier Protein; C548699:SLC19A1 protein, human; D013431:Sulfates; D012460:Sulfasalazine; D016685:Mitomycin; D005492:Folic Acid; D014700:Verapamil; D008727:Methotrexate