Downregulation of miR-409-3p expression in PTC tissues and cell lines compared with the corresponding controls. Reverse transcription-quantitative polymerase chain reaction was used to analyze the relative expression levels of miR-409-3p in (A) 20 surgically resected specimens of PTC tissues and matched non-tumor tissues, as well as in (B) three PTC cell lines (B-CPAP, TPC-1 and GLAG-66) and a normal human thyroid epithelial cell line (Nthy-ori3-1). Data are shown as the mean and standard deviation of expression levels relative to U6 expression levels. **P<0.01, ***P<0.001 vs. Nthy-ori3-1. PTC, papillary thyroid carcinoma; miR-409-3p, microRNA-409-3p.