GCLC and leukemia: We also treated leukemia cells with increasing doses of 4 interferents of GSH metabolism: phenethylisothiocyanate (PEITC) and piperlongumine (PL), which deplete GSH and increase ROS (50–52); hydrogen peroxide (H2O2), a ROS itself; and buthionine sulphoximine (BSO), a GCL inhibitor and, thus, a pharmacological inhibitor of GSH synthesis.