MicroRNA-21 promotes cell proliferation by targeting tumor suppressor TET1 in colorectal cancer

MicroRNAs (miRNAs) regulate gene expression by binding to mRNA, and can function as oncogenes or tumor suppressors depending on the target. TET1 acts as tumor-suppressor, which is downregulated in colorectal cancers (CRC) and inhibits cell growth. However, it has not been studied as to whether miRNAs, suppressing target expression by binding to the 3'UTR, regulate TET1 expression in colorectal cancers. Here, our study found that miR-21 has matching sites on TET1. In the tumor tissue samples from 50 patients with CRC, the expression of miR-21 was upregulated compared with that in adjacent tissue samples while the expression of TET1 showed a significant decrease. In addition, miR-21 expression was negatively correlated with the expression of TET1. Moreover, low expression of miR-21 by the transfection of colorectal cancer cell lines with miR-21 inhibitors, the effect on TET1 expression was opposite to the change of miR-21 expression. Furthermore, our results indicated that miR-21 promoted proliferation of colorectal cancer cells by targeting TET1. These findings may provide a theoretical basis for clarifying the physiological and pathological role of miR-21 in colorectal cancer.