a, Cell death following withdrawal of leucine (Leu) or arginine (Arg) determined using STACK. b, Representative images from ± Arg experiment shown in a. Scale bar = 25 μm. Representative images from one of three experiments are shown. c, Lipid ROS detected using C11 BODIPY 581/591 (C11) in U-2 OS cells treated for 24 h prior to imaging. Fer-1: ferrostatin-1. Scale bar = 20 μm. Imaging was performed twice and representative images from one experiment are shown. d, Cell death in -Arg medium resupplemented with 365 μM L-arginine (L-Arg), D-arginine (D-Arg), or citrulline, determined using STACK. e, Erastin2-induced cell death in cell lines grown in DMEM medium with dialyzed FBS ± Arg (356 μM) determined using STACK. Erastin2 was used at 1 μM (HT-1080N, Caki-1N, H23NCas9,N), 2 μM (T98GN, H1299N, U-2 OSN, A375N) or 4 μM (A549N) to achieve equal basal cell killing. f, Cell death at 48 h determined using STACK. In a, d-f results from three independent experiments are shown.