DNMT3B attenuated the inhibition of TET3 on epithelial-mesenchymal transition in TGF-β1-induced ovarian cancer by methylating the TET3 promoter

This study intends to investigate the effects of DNA methyltransferase 3B (DNMT3B) and ten-eleven translocation 3 (TET3) on transforming growth factor-β1 (TGF-β1)-induced epithelial-mesenchymal transition (EMT) in ovarian cancer (OV) cells. According to the specific experiments, the cells were treated with TGF-β1 for 48 h, and then the expressions of EMT-related proteins (E-cadherin, Vimentin and Snail), TET3 and DNMT3B were quantified by Western blot and quantitative reverse transcription polymerase chain reaction (qRT-PCR). Methprimer, methylation-specific PCR (MSP), bisulfite sequencing PCR (BSP) and chromatin immunoprecipitation (ChIP) were used to determine the regulation of DNMT3B on TET3 promoter. The impacts of DNMT3B and TET3 upon the EMT-related proteins and OV cell migration and invasion abilities were evaluated through the rescue experiments and the loss- and gain-of-function experiments. In line with the results, TGF-β1 down-regulated TET3 and E-cadherin levels, up-regulated Vimentin and Snail levels, promoted migratory and invasive abilities, and increased methylation level of TET3 promoter in OV cells, which however were reversed by shDNMT3B. The binding of DNMT3B to TET3 promoter facilitated the methylation of TET3 promoter. Overexpressed TET3 inhibited the migratory and invasive abilities and EMT of OV cells, whereas shTET3 did the opposite. ShTET3 also offset the regulatory effects of shDNMT3B on EMT, migration and invasion of OV cells. To conclude, DNMT3B mitigates the suppression of TET3 on TGF-β1-induced EMT in OV cells by methylating the promoter region of TET3.