Transport of methotrexate into LNCaP human prostate cancer cells.
Uptake of methotrexate into the LNCaP human prostate cancer cells was linear for the first 60 min. The initial rate of methotrexate uptake was highest at extracellular pH 4.5 and decreased markedly until pH 7.0 to 8.0. Transport of methotrexate into LNCaP cells showed two components, one saturable -K(m) = 0.13 +/- 0.06 microM and V(max) = 1.20 +/- 0.16 pmol x 45 min(-1) x mg(-1) protein at low concentrations and the other apparently not saturable up to 10 microM. Uptake of methotrexate was inhibited by structural analogs with the K(i) values being 6.53, 12.4, and 85.6 microM for 5-formyltetrahydrofolate, 5-methyltetrahydrofolate, and folic acid, respectively. Uptake of methotrexate into LNCaP cells was not inhibited by the energy poisons in contrast to methotrexate uptake into PC-3 prostate cancer cells. Uptake was inhibited by increasing concentrations of sulfate and phosphate ions and by the organic anions probenecid and DIDS, suggesting that methotrexate may be transported by an anion-exchange mechanism. These results show that methotrexate is transported into LNCaP prostate cancer cells by a carrier-mediated process.
Horne
Donald W
DW
Medical Research Service (151), VA Medical Center, Nashville, TN 37212, USA. donald.w.horne@vanderbilt.edu
Reed
Kathleen A
KA
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D008727:Methotrexate / Q000378:metabolism*; D010710:Phosphates / Q000494:pharmacology; D011339:Probenecid / Q000494:pharmacology; D011471:Prostatic Neoplasms / Q000378:metabolism*; D013431:Sulfates / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D010710:Phosphates; D013431:Sulfates; D011339:Probenecid; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D008727:Methotrexate