Fig. 4: PGE₂ increases oxidative stress in TILs by impairing the IL-2–mTOR–PGC1α axis, leading to ferroptosis.

a, Representative electron microscopy images of RA T cells with and without 24 h PGE₂ treatment (n = 3). Scale bar, 500 nm. b,c, Representative cristae number and length per mitochondrion in unstimulated and RA T cells upon 24 h PGE₂ treatment (n = 3). d, Fold change (relative to control) of mitochondrial potential (indicated by tetramethylrhodamine methyl ester (TMRM)) in CD39⁻ and CD39⁺ CD8⁺ TILs after 24 h PGE₂ treatment (n = 4). e, Fold change (relative to control) of oxidized/reduced glutathione quantified by ELISA in CD8⁺ TILs upon 24 h PGE₂ treatment with or without EP2/EP4 antagonists (n = 4). f, Relative PGC1A and PGC1B mRNA expression in TILs after 48 h PGE₂ (n = 6). g, Relative PGC1A mRNA expression in RA T cells treated with 12 h PGE₂ with or without an mTOR activator (MHY1485) and subsequently stimulated with IL-2 for 15 min (n = 6). h, Cell count of RA OT-1 mouse T cells overexpressing PGC1α (PGC1α OE) upon 72 h PGE₂ exposure (n = 4). i,j, Electron microscopy images (i; representative of three biological replicates) and mean number of lipid droplets per cell in unstimulated T cells and RA T cells upon 24 h PGE₂ exposure (n = 3). Scale bar, 3 μm. k, Lipid peroxidation in CD8⁺ TILs after 48 h PGE₂ exposure (n = 3). l, Fold change in GPX4 mRNA expression (exp.) in CD8⁺ TILs after 48 h PGE₂ (n = 5). m, Frequency of viable TILs after 72 h treatment with PGE₂ and indicated concentrations of Fst1 (ferroptosis inhibitor), MCC905 (pyroptosis inhibitor), z-vad-fmk (apoptosis inhibitor) or necrostatin 1S (necroptosis inhibitor) (n = 3). Two-way ANOVA with Dunnett’s post test; *P < 0.05, **P < 0.01, ***P < 0.001. n, MDA quantification in CD8⁺ TILs upon 48 h PGE₂ exposure with or without EP2/EP4 antagonists, using ELISA (n = 5). o, Relative cell count of TILs upon 72 h PGE₂ exposure with or without NAC or vitamin E (VITE) (n = 6). Data are mean ± s.d. Paired two-tailed t-test (k,l); one-way ANOVA with Dunnett’s post hoc test for multiple comparisons (b–h,j,n,o). Independent biological samples were used; exact numbers of biological replicates are listed in each panel.