CAT and neoplasm: Particularly, GDY-CeO2 exhibited a better catalase activity by transforming H2O2 into O2 when surrounded by a weakly acidic tumor microenvironment, which caused the mitigation of tumor hypoxia (therefore reversing radioresistance), promoted radiation-induced DNA damage, inhibited tumor growth, and enhanced radiotherapy sensitivity in esophageal squamous cell carcinoma (ESCC) (Zhou et al., 2021).