GPX4 and cancer: As a third possibility, as the xCT-positive cancer cells are expected to have increased glutathione production and GPX4 expression, the resulting increased antioxidant capacity may be accompanied by a reduced selective requirement for other anti-ferroptotic or prosurvival signaling activities, meaning that when this xCT/GPX4-mediated protection is removed, these cancer cells are vulnerable compared to ‘nonaddicted’ cells.