In line with the results we observed previously (24), tumor-reactive GPX4–/– CD8+ T cells lost their antitumor activity (Figure 3N) with fewer tumor-infiltrating transferred CD8+ T cells (Figure 3O) and decreased IFN-γ production (Figure 3P) and Ki67 expression (Figure 3Q) compared with control CD8+ T cells. The gene discussed is MKI67; the disease is neoplasm.