Inhibition of MicroRNA-346 Exerts Positive Effects on Estrogen-Associated Molecular and Behavioral Traits in Follicular Thyroid Carcinomas

Abstract Background The gender disparity in the thyroid cancer incidence rate, which is 3-folds higher in women than in men, has been hypothesized to be related to estrogen and estrogens receptors (ERs). Recent evidence suggests that nuclear receptor-interacting protein 1 (NRIP1) is known as a coregulator of ERs and a direct target of microRNA-346 (miR-346), which was reported as a biomarker for follicular thyroid carcinoma (FTC). In this study, we investigated the roles of miR-346 on behavioral traits and estrogen-associated pathogenesis of FTCs. Methods Two Human follicular thyroid carcinomas (FTC-133 and RO82-W-1) were used. To examine the effects of miR-346 and estrogen on behavioral traits and estrogen-associated pathogenesis of FTCs, FTC-133 and RO82-W-1 were transfected with the inhibitor targeting human miR-346 or the non-specific miR (-Control), then were treated with 100nM or 200nM of estradiol-17 β (E2). Cell migration and invasion assays were performed; gene and protein levels of NRIP1, ERα, and ERβ were examined by qPCR and western blot, respectively. In addition, cell cycle-regulating genes, epithelial biomarkers, mesenchymal biomarkers were also examined. Results E2 decreased the number of invaded and migrated cells regardless of miR-346-downregulation in both FTCs. Downregulation of miR-346 itself also had protective effects on invasion and migration of both FTCs, and it augmented the inhibitory effects of E2. E2 decreased both gene and protein levels of NRIP1 in FTC-133 while miR-346 downregulation did in RO82-W-1. E2 and miR-346 downregulation decreased the gene and protein expressions of ERα while it increased ERβ, accordingly, decreasing the ratio of ERα to ERβ in both FTCs. E2 significantly decreased cellular proliferation in miR-346 downregulated FTCs. These support that miR-346 has significant roles in estrogen-associated pathogenesis of FTCs by regulating NRIP1 and the interaction of ERα and ERβ. Downregulation of miR-346 increased gene expressions of occluding and cloudin-1 (CLDN1) while decreasing vimentin in FTC-133, it significantly increased gene expressions of CLDN1 in RO82-W-1. These suggest miR-346 in involved in maintaining integrity of FTCs. Conclusion Inhibition of miR-346 in FTCs have protective effects on metastasis, thereby, miR-346 is suggested as a therapeutic target for FTC.