Effect of human EPO on IL-6–induced hepcidin expression in PLC/PRF/5 cells. IL-6–induced hepcidin mRNA expression in PLC/PRF/5 cells was suppressed by rEPO. An approximately 6-fold increase in hepcidin mRNA expression was observed in cells stimulated with IL-6 (10 ng/mL) compared with nonstimulated controls. rEPO suppressed IL-6–induced hepcidin expression in a dose-dependent manner (0.1-100 U/mL), whereas 100 U/mL rEPO led to maximal inhibition of IL-6–induced hepcidin mRNA expression (50% reduction).