miR-29a inhibits proliferation, invasion, and migration of papillary thyroid cancer by targeting DPP4

Purpose: The purpose of this study was to investigate the effects of miR-29a on papillary thyroid cancer (PTC) and its underlying mechanisms. Methods: Primary tumor tissues and adjacent tissues of 69 patients with PTC were obtained. Human thyroid cell line Nthy-ori3-1 and PTC cell lines K1, BCPAP, TPC-1 were cultured. K1 cells were transfected and divided into following groups: blank group (without any treatment), miR-29a mimics group, control mimics group, miR-29a inhibitor group, control inhibitor group, DPP4 siRNA group, control siRNA group and miR-29a inhibitor + DPP4 siRNA group. qRT-PCR and Western blot were used to detect miR-29a and DPP4 expression. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and transwell assay were performed to detect cells proliferation, migration, and invasion. A nude mice xenograft experiment was performed. Results: miR-29a was significantly downregulated in PTC tissues, K1 and TPC-1 cells (P<0.01). DPP4 was significantly upregulated in the miR-29a inhibitor group and significantly downregulated in the miR-29a mimics group (P<0.01). DPP4 was the target gene of miR-29a. miR-29a significantly inhibited K1 cell proliferation, invasion, migration and PTC growth in nude mice by targeting DPP4 (P<0.01). Conclusion: miR-29a inhibits proliferation, migration, and invasion of PTC by targeting DPP4, which might provide a new target for clinical treatment of PTC.