LAUSR

OBJECTIVE Papillary thyroid cancer (PTC) is the most ordinary type of thyroid cancer. Studies pivoting on the mechanisms of microRNAs (miRNAs) are adequately explored but not much on miR-448 in PTC. Thus, this study is proposed to bring forward the uncovered mechanisms of miR-448 in PTC. METHODS Lysine specific demethylase 5B (KDM5B), miR-448 and transforming growth factor β-induced factor 1 (TGIF1) expression in PTC tissues and cell lines were detected. The connection between miR-448 expression and clinicopathological characteristics of PTC patients was determined. PTC cell lines TPC-1 and K-1 were transfected with sh-KDM5B, si-TGIF1 or miR-448 mimic to explore their roles in PTC cell progression. Tumor xenografts in nude mice was performed to detect tumor volume and weight. RESULTS KDM5B and TGIF1 were increased and miR-448 was declined in PTC tissues and cell lines. MiR-448 expression was connected with N stage, lymph node metastasis and advanced tumor node metastasis stage of PTC patients. KDM5B knockdown or TGIF1 reduction or miR-448 elevation undermined PTC cell progression and inhibited tumor growth of nude mice. Down-regulation of miR-448 followed by KDM5B knockdown reversed the effect of decreased KDM5B on the proliferation inhibition and apoptosis promotion of PTC cells. CONCLUSION Our study elaborates that KDM5B-mediated miR-448 up-regulation restrains PTC cell progression and slows down tumor growth via TGIF1 repression, which provides a novel reference for treatment of PTC.