STAT3 mediates hepcidin expression. (A) Luciferase reporter assays. Huh7 cells were transfected with the –942 bp or the –942 bp ΔSTAT luciferase reporter vectors, and luciferase activity was measured after 48 hours. Transfections were performed in triplicates, and results are presented as a fold change ± SD of firefly/Renilla (F/R). (B) siRNA-mediated knockdown of STAT3. Hepcidin mRNA expression in Huh7 cells was assayed after transfection with specific siRNAs directed against STAT3 or luciferase (Luc siRNA) as a control. Hepcidin and STAT3 mRNA expression was analyzed by quantitative real-time PCR and data normalized to mRNA expression of a housekeeping gene, Gapdh. Data are presented as fold change, whereby Huh7 cells transfected with the luciferase control siRNA were set to 100%. STAT3 mRNA expression was reduced to 12%. Significant expression changes are marked by an asterisk, whereby * represents P < .05 and ** represents P < .005.