CAT and neoplasm: Other studies have shown that increased ROS levels cause oxidative damage to cellular structures and decrease antioxidant enzymes SOD and CAT activity in tumor tissue compared to the SEC group, as SOD catalyzes the dismutation of superoxide anion (O2) to H2O2 and O2, and the CAT enzyme reduces H2O2 to H2O. Interestingly, treatment with ZnO-NPs revealed a marked increase in MDA levels, which indicates lipid peroxidation and depletion of GSH in ESC tissues (25).