Overexpression of miR-100-5p inhibits papillary thyroid cancer progression via targeting FZD8

Papillary thyroid cancer (PTC) is the most prevalent type of TC worldwide; however, its pathological process remains unclear at the molecular level. In the current study, we analyzed the microarray data of PTC tissues and non-neoplastic thyroid tissues, and confirmed miR-100-5p as a downregulated miRNA in PTC. Via bioinformatic approach, western blotting, and TOP/FOP-flash assay, miR-100-5p was observed to be involved in the inactivation of Wnt/β-catenin signaling in TPC-1 and KTC-1. Frizzled Class Receptor 8 (FZD8), the coupled receptor for canonical Wnt/β-catenin signaling, was verified to be targeted and inhibited by miR-100-5p in TPC-1 and KTC-1. In the function assay, miR-100-5p mimic repressed PTC cell proliferation and induced cell apoptosis of TPC-1 and KTC-1; meanwhile, transfection of full-length FZD8 attenuated the effect of miR-100-5p mimic. Moreover, in the collected samples, miR-100-5p was lowly expressed in PTC tissues compared with normal tissues, especially in those of advanced stage (Stage III/IV vs Stage I/II), while FZD8 was highly expressed in PTC tissues, which in PTC tissues was inversely correlated to miR-100-5p. Thus, we suggest that overexpression of miR-100-5p inhibits the development of PTC by targeting FZD8.