GPX4 and neoplasm: Therefore, Cro‐Fe@BSA had an ability to react with high level concentration of GSH in the acidic TME of tumor cells, consume GSH, and degrade to obtain Fe2+. All the functions together enabled the expression of GPX4 decrease, and the obtained Fe2+ further reacted with H2O2 in tumor to generate ROS increasing the level of lipid peroxide in tumor cells and decreasing the expression of heat shock protein 70 (HSP70), and finally induced 4T1 tumor cell ferroptosis.