The Indoleamine-2,3-Dioxygenase (IDO) Inhibitor 1-Methyl-D-tryptophan Upregulates IDO1 in Human Cancer Cells
Figure 6
1-D-MT upregulates IDO1 expression and kyn release induced by different concentrations of IFN-γ in diverse cancer cells.
(A) Representative HPLC graphs of kyn production of HeLa cells, which were either untreated, treated with 1 mM 1-D-MT and/or 1000 U IFN-γ for 72 h. Absorption of kyn was measured at 365 nm. (B) In untreated HeLa cells 1 mM 1-D-MT did not induce de novo IDO1 mRNA, but increased IDO1 mRNA after its induction by 1000 U IFN-γ mRNA expression was analyzed by qRT-PCR 24 h after treatment. (C) Representative example of the effect of different IFN-γ concentrations on IDO1 mRNA induction by 1-D-MT, shown in U251 glioma cells. (D) IDO1 mRNA expression of indicated cell lines that were stimulated for 24 h with appropriate concentrations of IFN-γ alone (white bars) or in combination with 1 mM 1-D-MT (black bars). (E) Representative example of IDO1 mRNA induction by 200 µM 1-D-MT in IFN-γ-stimulated T98G glioma cells. (F) Kyn release of indicated cell lines that were stimulated for 72 h with appropriate concentrations of IFN-γ alone (white bars) or in combination with 1 mM 1-D-MT (black bars), measured by HPLC. Experiments were performed in triplicate. Data are mean ± SEM. * (p<0.05).