The role of GSH in MRP-mediated CDDP transport. De novo biosynthesis of GSH is carried out by $\gamma$-GCS, which conjugates glutamine (Glu) and cysteine (Cys) followed by GSH synthetase using glycine (Gly) as a substrate. GSH can be oxidized into GSSG by GSH peroxidase. SOD refers to superoxide dismutase. GSSG can be reduced to GSH by GSSG reductase. GSSG is a substrate of the MRP/GS-X pump whereas GSH functions as a cofactor for MRP-mediated CDDP transport.