TET1 and neoplasm: Additionally, those previous studies have reported that TET1 plays roles in not only tumor suppression but also promotion during tumorigenesis and progression by regulating gene expression in a multilayered manner, including acting as transcription factor and regulating the 5hmC level.16, 31 Furthermore, in terms of chemoresistance in cancer, only a few studies have focused on the role of TET1 and its potential mechanisms.