This was independently confirmed by both siRNA silencing and warfarin knock-down of VKOR enzymatic activity in human hepatoma HepG2 cells after Ero1 α/β isoforms and peroxiredoxin IV (PRDX4) were first functionally silenced, demonstrating that VKORC1 alone can facilitate OPF. Here, PRDX4 is linked to hepatocellular carcinoma.