Figure 3.

Effects of EGCG on the phosphorylation of STAT1 protein and transcriptional activity of IDO promoter in SW837 cells. (A) Cells were pretreated with various concentrations of EGCG for 2 h and were then stimulated with IFN-γ for 30 min. Total cellular protein was extracted and the expression of phosphorylated STAT1 protein was determined by western blot analysis. (B) Transient transfection reporter assays using ISRE and GAS luciferase reporter plasmids were performed using cell extracts pretreated with various concentrations of EGCG for 2 h and then stimulated with IFN-γ for 24 h. Columns and bars indicate the mean and SD. IFN, interferon; EGCG, (-)-epigallocatechin gallate; STAT1 signal transducer and activator of transcription 1; ISRE, interferon-stimulated response element; GAS, IFN-γ activation sequence; IDO, indoleamine 2,3-dioxygenase; SD, standard deviation.