DMF treatment induces ferroptosis in DLBCL. (A) Reduced glutathione levels were quantified in various DLBCL cell lines and normalized to the myeloid cell line THP-1. (B) The indicated cell lines were treated with 20 μM of DMF for 2 hours. The ratio of reduced to oxidized glutathione was determined and normalized to the respective solvent-treated controls. (C) Lipid peroxidation was quantified by flow cytometry using the oxidation-sensitive fluorescent probe BODIPY C11. GCB DLBCL cell lines were treated with solvent or the indicated amounts of DMF and erastin for 2 and 8 hours, respectively. (D-E) GCB (D) and ABC (E) DLBCL cell lines were treated with solvent or 20 μM DMF alone, or in combination with 5 μM Fer-1 for 24 (D) and 48 (E) hours. Cell numbers were determined and normalized to the solvent control. (F) DOHH2 and SU-DHL-6 cells were treated with 20 μM DMF alone, or in combination with 5 μM Fer-1, 100 μM α-tocopherol, 100 μM DFX, or 20 μM Q-VD. Survival was quantified by MTS assay after 24 hours. (G-H) Quantification of lipid peroxidation in DMF-treated control and FLAG-RelA–overexpressing GCB DLBCL cells. The mean fluorescence intensity (MFI) of oxidized BODIPY C11 in DMF-treated cells was normalized to the MFI of the respective solvent-treated samples. (I) DOHH2 cells expressing FLAG-RelA or control vector were counted and treated daily with 20 μM DMF for 6 days. Cell counts were normalized to the solvent control. Error bars correspond to the mean ± standard deviation. Data are representative of ≥2 (A-B) or ≥3 (C-I) independent experiments. Statistical significance was calculated using the Student t test. *P < .05, **P < .01, ***P < .001.