TCF4 and infection: To determine the optimal time for HCVinfection, the viability of the PTHs was evaluated using a3-(4,5-dimethylthiazol-2-yl)−2,5-diphenyltetrazolium bromide (MTT) assay.As shown in Fig. 1(a, b), a decrease in thecell proliferation of PTHs was observed after 17 days of culture.Therefore, the infection of PTHs with HCV was carried out for 17 days ofincubation in subsequent experiments.