A, B, C ZIP7 knockdown conferred resistance to cystine-deprivation or erastin mediated ferroptosis in MDA-MB-231 cells. A MDA-MB-231 cells were transfected with two independent siRNAs targeting ZIP7 for 48 h and treated with the cystine-deficient medium. B The knockdown efficiency of both ZIP7 siRNA in MDA-MB-231 was validated by the lower levels of ZIP7 protein (arrow) using Western blots. C MDA-MB-231 cells were transfected with indicated siRNA for 72 h and treated with 5 μM erastin for an additional 22 h before measuring the viability with CellTiter-Glo®. D, E, F ZIP7 knockdown conferred resistance to erastin-mediated ferroptosis in a zinc-dependent manner. D RCC4 cells were treated with non-targeting (NC) or individual ZIP7 siRNA for 48 h, followed by treatment of 100 μM ZnCl2, 2.5 μM erastin, or combination for an additional 24 h. E MDA-MB-231 cells were treated with siNC and ZIP7-targeting siRNAs for 50 h, followed by treatment of 100 μM ZnCl2, 10 μM erastin, or combination for 18 h. F The knockdown efficiency of ZIP7 siRNA in MDA-MB-231 was validated by Western blots (arrow for ZIP7). G, H ZIP7 inhibitor protected against erastin-mediated ferroptosis. MDAMB231 or RCC4 cells were pretreated with ZIP7 inhibitor (NVS-ZP7-4 (48 h for 231 and 24 h for RCC4) followed by the addition of erastin for an additional 24 h. The cell viability was measured by CellTiter-Glo®. The data were represented as mean ± SD (n = 3; **p < 0.01; ****p < 0.0001; two-way ANOVA).