As DNA methylation is essential for gene expression and TET1 alters methylation status of CpG islands, to investigate the mechanism of TET1 suppresses cell proliferation, migration and invasion of gastric cancer cell, we chose four tumor suppressor genes as candidates which were canonically modulated by promoter methylation status i.e. PTEN, p53, hMLH1 and IRX1. The gene discussed is MLH1; the disease is neoplasm.