Aspartate-modified doxorubicin on its N-terminal increases drug accumulation in LAT1-overexpressing tumors.
Bottom Line: In vitro, Asp-DOX exerted stronger inhibition on the cancer cells overexpressing LAT1 and the uptake of Asp-DOX was approximately 3.5-fold higher than that of DOX in HepG2 cells.Pharmacokinetic data also showed that Asp-DOX was expressed over a longer circulation time (t1/2 = 49.14 min) in the blood compared to DOX alone (t1/2 = 15.12 min).Furthermore, after Asp modification, Asp-DOX avoided MDR mediated by P-glycoprotein.
Affiliation: School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.Show MeSH
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Mentions: LAT1-mediated L-[3H] leucine uptake (2Ā Ī¼mol/L) was measured in the presence of 100Ā Ī¼mol/L concentrations of non-labeled compounds (Fig.1). As shown in Figure1(a), L-[3H] leucine uptake was markedly inhibited by Asp-DOX and Tyr-DOX, especially Asp-DOX, whereas the other compounds (Leu-DOX, Val-DOX, Met-DOX, Phe-DOX, and Ile-DOX) barely inhibited the uptake of L-[3H] leucine by S2-LAT1. Furthermore, in order to check the inhibition of Asp-DOX to the uptake of L-leucine, we inspected its IC50 (Fig.1b). Asp-DOX exerted high inhibition on the uptake of L-leucine and its IC50 to L-leucine was determined to be approximately 30.12Ā Ī¼mol/L. In order to check whether the internalization of Asp-DOX was mediated by LAT1, the inhibition to the uptake of Asp-DOX by different amino acids (Leu, Met, and Phe, substrates of LAT1; Ala, Glu, and Gly, non-substrates of LAT1) was determined with or without 100Ā Ī¼mol/L amino acids. The results showed that 100Ā Ī¼mol/L Leu, Met, and Phe strongly inhibited the uptake of Asp-DOX, whereas 100Ā Ī¼mol/L Ala, Glu, and Gly had no inhibition (Fig.1c). However, neither 100Ā Ī¼mol/L Leu, Met, or Phe, nor 100Ā Ī¼mol/L Ala, Glu, or Gly inhibited the uptake of DOX by S2-LAT1 cells (Fig.1d). In order to check the affinity of Asp-DOX to LAT1, the MichaelisāMenten curve was plotted. The results showed that the Km of Asp-DOX with LAT1 was determined as 41.423Ā Ī¼mol/L (Fig.1e). These results suggested that the internalization of Asp-DOX into S2-LAT1 cells was mainly mediated by LAT1.
Affiliation: School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.