Peptide transporters are expressed predominantly in intestinal and renal epithelial cells. The functional expression of
peptide transporters is also identified in other types of tissues, such as glia cells, macrophages, and the epithelia of the bile duct, the lungs, and the mammary glands. However, their presence and role are poorly understood in
carcinomas. We explored the expression profile and functional activity of
peptide transporters in the
prostate cancer cell lines LNCaP, PC-3, and DU145. Quantitative real time RT-PCR (qRT-PCR) and Western blot were used to evaluate the expression profile of
peptide transporter 1 (PEPT1),
peptide transporter 2 (PEPT2),
peptide histidine transporter 1 (PHT1), and
peptide histidine transporter 2 (PHT2) in these cells. LNCaP expresses high levels of PEPT2 and PHT1, while PC-3 demonstrates strong expression of PEPT1 and PHT1. DU145 shows only weak expression of PEPT1 and PHT1. Functional activities were studied in these cell lines using radiolabeled
glycylsarcosine ([(3)H]
Gly-Sar) and
l-histidine ([(3)H]-
l-histidine). The uptake of [(3)H]
Gly-Sar and [(3)H]-
l-histidine was time- and pH-dependent. A kinetic study showed that the uptake of
Gly-Sar and
l-histidine is saturable over the tested concentration range. The binding affinity (K(m)) and the maximal velocity (V(max)) exhibited in the three cell lines were consistent with the expression profiles we observed in qRT-PCR and Western blot analysis. A competitive inhibition study revealed that
peptide transporters in
prostate cancer cells exhibited broad substrate specificity with a preference for hydrophobic
dipeptides, such as
Leu-Leu. Fluorescence microscopy study revealed that the fluorescent
dipeptide probe d-
Ala-Lys-AMCA (a substrate of
peptide transporters) specifically accumulated in the cytoplasm of LNCaP and PC-3, but not DU145 cells. Inhibiting the
peptide transporter activity by
Gly-Sar suppressed the growth of LNCaP and PC-3 cells. Our study indicated that PC-3 cells can be established as a new cell culture model for PEPT1 study, and LNCaP can be used as a model for PEPT2 study. Moreover, our results suggested that
peptide transporters are overexpressed in
prostate cancer cells and can be adopted as a promising target for
tumor-specific
drug delivery.