GPX4 and ovarian cancer: (3) Sulfur amino acid axis: xCT (SLC7A11) promotes cystine uptake for GSH synthesis, while GPX4 limits lipid peroxidation; xCT/GPX4 upregulation is associated with platinum resistance in ovarian cancer, and their inhibition triggers ferroptosis and reverses tolerance [62,63,64] (Figure 2C).