NQO1 and hepatoblastoma: To assess the synergistic effect of NQO1 inhibition and doxorubicin on NQO1-high hepatoblastoma cell lines, we performed a drug sensitivity assay, which revealed that both NQO1 siRNA and dicoumarol, an NQO1 inhibitor, significantly lowered the EC50 values of doxorubicin (Fig. 4c, d and Supplementary Fig. 11, a, b).