GPX4 and cancer: In the context of anti-cancer treatment, an increasing amount of data points to two major targets for ferroptosis induction in tumor cells—the cystine-glutamate exchanger (Xc- system, or more precisely, its transporter subunit known as xCT and its chaperon CD98) and the glutathione peroxidase 4 (GPx4), that are, respectively, involved in the maintenance of the cysteine intracellular pool and the removal of the oxidative damages of plasma membrane lipids, preventing ferroptosis [2,3,4].