miR-219-5p Modulates Cell Growth of Papillary Thyroid Carcinoma by Targeting Estrogen Receptor α

Context: Papillary thyroid carcinoma (PTC) is the most common endocrine malignancy. It has been demonstrated that micro-RNAs (miRNAs) are involved in the development of PTC. The miRNA-chromatin immunoprecipitation microarray assay revealed down-regulation of miR-219-5p; however, the effect of miR-219-5p on PTC cell growth remains unknown. This result implied the critical role of miR-219-5p in the development of PTC. Methods: We investigated the association between miR-219-5p and PTC development. Expression of miR-219-5p was monitored in 30 PTC tissue specimens and compared with that in 30 normal thyroid tissue specimens. The effect of miR-219-5p on PTC development was studied by cell proliferation, migration, and apoptosis assays. The underlying mechanism was clarified by a reporter assay and rescue experiment. Results: The current study confirmed that miR-219-5p expression was inhibited in PTC tissue samples. There were statistically significant differences in the expression of miR-219-5p with regard to sex, tumor size, and lymph node metastasis in patients with PTC. Forced expression of miR-219-5p suppressed PTC cell proliferation and migration and promoted apoptosis. Further study showed that estrogen receptor (ER)alpha was the direct target of miR-219-5p and mediated the effect of miR-219-5p on PTC occurrence. Expression of miR-219-5p was inversely correlated with that of ER alpha. Importantly, ER alpha overexpression in PTC cells rescued the inhibitory effect of miR-219-5p on PTC cell proliferation and migration. Thus, our results indicated that miR-219-5p played a critical role in PTC growth by inhibiting ER alpha. Conclusion: Our investigation identified miR-219-5p as a negative regulator of PTC development through targeting of ER alpha.