Recent study of Tet1 were about cancer, 5hmC got lower level in patients with breast cancer, liver cancer, lung cancer, pancreatic cancer and gastric cancer13, 48, 49, 50, 51, 52, 53, which showed down-regulation of Tet1 may lead to cancer and Tet1 act as a tumor suppressor in epigenetic modification. The gene discussed is TET1; the disease is familial pancreatic carcinoma.