MicroRNA‑409‑3p suppresses cell proliferation and cell cycle progression by targeting cyclin D2 in papillary thyroid carcinoma

MicroRNAs (miRs) function as tumor suppressors or oncogenes in tumor development and progression. The present study reported that miR-409-3p was significantly downregulated in human papillary thyroid carcinoma (PTC) tissues and cell lines. Overexpression of miR-409-3p suppressed cell proliferation and induced cell cycle G0/G1 phase arrest in PTC cells. Further study revealed that the transcriptional regulator cyclin D2 was a target of miR-409-3p, as miR-409-3p bound directly to its 3'-untranslated region and the miR-409-3p mimic reduced the protein expression levels of cyclin D2. In addition, restoration of cyclin D2 expression reversed the inhibitive effect of miR-409-3p on PTC cells. To the best of our knowledge, these findings demonstrate for the first time that miR-409-3p functions as a tumor suppressor in PTC and could serve as an efficient agent for therapy of PTC.