CASP3 and neoplasm: Moreover, the expression of prostaglandin-endoperoxide synthase 2 (PTGS2, a marker of ferroptosis, but not the driving factor of ferroptosis)10 and Ki67 (a marker of tumor cell proliferation), but not cleaved caspase-3 (a marker of apoptosis) and phosphorylated mixed lineage kinase domain-like pseudokinase (p-MLKL, a marker of necroptosis), in the pancreas was upregulated by either Gpx4 depletion or a high-iron diet in Kras-driven pancreatic tumorigenesis (Fig. 2f and Supplementary 3f).