title: Carrier-mediated transport of oligopeptides in the human fibrosarcoma cell line HT1080.
abstract: To explore the feasibility of targeting human tumor cells via their transport systems, dipeptide uptake was studied in the human fibrosarcoma cell line HT1080 and the human fibroblast cell line IMR-90 by the use of hydrolysis-resistant glycylsarcosine (Gly-Sar). The uptake of [14C]Gly-Sar into HT1080 was time dependent. Kinetic analysis of the concentration dependence of the initial rate of [14C]Gly-Sar uptake showed that a carrier-mediated transport system with a K(m) of 11.4 +/- 3.3 mM and V(max) of 26.8 +/- 4.0 (nmol/15 min/mg protein) and a nonsaturable component (k(d) of 0.80 microl/15 min/mg protein) were responsible for the dipeptide uptake by HT1080 cells. The optimal pH for the maximal uptake was around 6.0. [14C]Gly-Sar uptake was inhibited by various di- and tripeptides and peptide-mimetic drugs, such as bestatin and cefadroxil. [14C]Gly-Sar uptake was not affected by the presence of amino acids or tetra- or pentapeptides. The uptake of cefadroxil was reduced significantly by unlabeled Gly-Sar. Moreover, Gly-Gly and Gly-Leu produced an increase in the apparent K(m) of the uptake of Gly-Sar without altering V(max). On the other hand, dipeptide uptake by IMR-90, which is a normal diploid cell line (not malignant), showed no saturable transport. These results suggest that HT1080 cells take up dipeptides via a pH-dependent transporter. This is the first report showing that a dipeptide transport system, which is similar but not identical to the well-characterized oligopeptide transporters PepT1 and PepT2, exists in fibroblast-derived tumor cells but not in normal fibroblasts. The present finding could be the basis of a novel strategy for the specific delivery of oligopeptide-mimetic anticancer drugs into tumor cells.
authors.affiliation: Department of Pharmacobio-dynamics, Faculty of Pharmaceutical Sciences, Kanazawa University, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Nakanishi
authors.forename: I
authors.initials: I
authors.lastname: Tamai
authors.forename: Y
authors.initials: Y
authors.lastname: Sai
authors.forename: T
authors.initials: T
authors.lastname: Sasaki
authors.forename: A
authors.initials: A
authors.lastname: Tsuji
mesh_terms: D001692:Biological Transport; D005347:Fibroblasts / Q000378:metabolism; D005354:Fibrosarcoma / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009842:Oligopeptides / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013696:Temperature; D014407:Tumor Cells, Cultured
chemical_list: D009842:Oligopeptides