*3.2.4. Dual function of miRNA by interaction with Tet mRNA 3'UTRs*

Some miRNAs are reported to function as both a suppressor and a promoter in some cancers such as miR29b in breast cancer (BC) cells by regulation of BC cell proliferation, metastasis, and epithelial-mesenchymal transition (EMT). Significantly decreased expression of miR-29b in BC samples and cell lines suggests the role of TET1 as a BC suppressor. However, miR-29b overexpression promotes cell proliferation, colony formation, migration, and EMT, indicating that miR-29b functions as a BC promoter [103]. In vitro assay TET1 has been identified as one of the miR-29b targets, and it turns out that overexpression of miR29b leads to TET1 downregulation-mediated promotion of proliferation, colony formation, invasion, and EMT in GC cells such as MDA-MB-231 and MCF-7. Further study showed that the TET1-mediated suppression of the BC attributed to TET1 conferred disruption of ZEB2 expression by binding to the promoter of ZEB2. While the miR-29b/TET1/ZEB2 pathway offers understanding for the mechanism of miR-29b and TET1-mediated BC promotion, the suppression mechanism for TET1 remains to be elusive in GC [104].
