Different types of malignant tumors have abnormal hypermethylation of the GPX3 promoter and low levels of the GPX3 protein expression, such as thyroid and colorectal tumors [4], Barrett's tumor, prostate and breast cancers, cervical and breast cancers, esophageal cancers, and leukemia and hepatocellular carcinomas. The gene discussed is GPX3; the disease is esophageal cancer.