Affiliations: Medical Research Service (151), VA Medical Center,
Nashville, TN 37212, USA | Department of Biochemistry, Vanderbilt University
School of Medicine, Nashville, TN 37232, USA
Note: [] Corresponding author: Donald W. Horne, F512 ACRE Building (151),
1310 24th Avenue, South, VA Medical Center, Nashville, TN 37212, USA. Tel.: +1
615 327 4751 ext. 5474; Fax: +1 615 321 6305; E-mail:
donald.w.horne@vanderbilt.edu
Abstract: 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 μM and
V_{max} = 1.20 ± 0.16 pmol ·
45 min^{-1} · mg^{-1} protein at low concentrations and the other
apparently not saturable up to 10 μM. Uptake of
methotrexate was inhibited by structural analogs with the
K_i values being 6.53, 12.4, and
85.6 μM 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.
Keywords: methotrexate, transport, LNCaP cells, prostate, prostate cancer cells
Journal: BioFactors, vol. 16, no. 1-2, pp. 19-27, 2002
