TET enzymes and 5hmC epigenetic mark: new key players in carcinogenesis and progression in gynecological cancers.

DNA methylation is an epigenetic mechanism involving the transfer of a methyl group onto the C5 position of the cytosine to form 5-methylcytosine (5mC). In general, DNA methylation in cancer is associated with the repression of the expression of tumor suppressor genes (TSG) and the demethylation with the overexpression of oncogenes. DNA methylation was considered a stable modification for a long time, but in 2009, it was reported that DNA methylation is a dynamic modification. The Ten-Eleven-Translocations (TET) enzymes include TET1, TET2, and TET3 and participate in DNA demethylation through the oxidation of 5mC to 5-hydroxymethylcytosine (5hmC). The 5hmC oxidates to 5-formylcytosine (5fC) and 5-carboxylcitosine (5caC), which are replaced by unmodified cytosines via Thymine-DNA Glycosylase (TDG). Several studies have shown that the expression of TET proteins and 5hmC levels are deregulated in gynecological cancers, such as cervical (CC), endometrial (EC), and ovarian (OC) cancers. In addition, the molecular mechanisms involved in this deregulation have been reported, as well as their potential role as biomarkers in these types of cancers. This review shows the state-of-art TET enzymes and the 5hmC epigenetic mark in CC, EC, and OC.