TET1 and intrahepatic cholangiocarcinoma: The decreased TET1 expression helps the methylated CpG‐rich segments at a promoter site of the p53 gene to stay methylated, resulting in down‐regulation of p53, thereby disrupting the anti‐cancer function of p53. Overall, the up‐regulated miR‐191 is related to intrahepatic cholangiocarcinoma progression via the miR‐191/TET1/p53 pathway.56 Furthermore, miR‐520b inhibits cell proliferation by reducing the expression of TET1.57 In this process, however, TET1 may act as an oncogene, and this notion contradicts results of a previous study.