miR-29b upregulates miR-195 by targeting DNMT3B in tongue squamous cell carcinoma

MicroRNAs play important roles in the development and progression of various cancers, including tongue squamous cell carcinoma (TSCC). miR-29b and miR-195 have been reported to be tumor suppressors in TSCC. Here, we investigated the expression of miR-29b and miR-195 and their relationship in TSCC. Our data showed that miR-29b and miR-195 were significantly downregulated in TSCC compared with their matched nonmalignant tissues in 60 paired samples. The level of miR-29b was positively correlated with that of miR-195 in TSCC and the matched nonmalignant tissues. Moreover, miR-29b overexpression induced the demethylation of CpG islands upstream of miR-195 via targeting DNMT3B, leading to the upregulation of miR-195 in TSCC cell lines. Following DNMT3B silencing, the expression of miR-195 was increased and the methylation of CpG islands upstream of miR-195 was reduced. Although overexpression of miR-29b alone significantly increased miR-195 expression, co-transfection of miR-29b with DNMT3B resulted in no change in miR-195 expression. Taken together, our results demonstrated that miR-29b could upregulate miR-195 by directly targeting DNMT3B in TSCC. The interaction between miR-29b and miR-195 might provide new insights in developing novel therapeutic approaches of TSCC.