Likewise, the inhibition of GSH synthesis by buthionine sulfoximine (BSO) or depletion of extracellular cystine by cyst(e)inase also promotes GSH depletion and ROS accumulation, which can potentiate the sensitivity of cancer cells to ferroptosis inducers and suppress tumor growth, since GPX4 requires GSH as a cofactor [20,21]. This evidence concerns the gene GPX4 and cancer.