Expression of miRNA 146a/b, 221 and 222 in Thyroid Cancer.

Background: miRNAs can be diagnostic markers and therapeutic targets in cancers, but few studies have been conducted in thyroid cancer. We investigated the expression levels of miRNA 146a/b, 221, and 222 which are important miRNAs in papillary thyroid cancers (PTCa), and verified their impact on clinicopathological factors. Methods: We measured the expression of pre-miRNAs 146a/b, 221, and 222 in NPA cells treated with 10% fetal bovine serum (FBS) or in HEK293T cells transfected with RET/PTC3 or BRAF V600E expression vectors. We also investigated the relationship between miRNA expression levels in thyroid cancer tissue specimens and clinicopathological parameters. Results: Growth stimulation with 10% FBS induced miRNA expressions in NPA cells, and transfection of RET/PTC3 and BRAF V600E also increased the expression of these miRNAs in HEK293T cells. Most (25 cases; 50%) of PTCa showed increased expression of miRNA-146a/b and 30 cases (60%) had elevated expression of miRNA-221 and miRNA-222 compared to normal thyroid samples from the contralateral lobe. However, increased miRNA expression did not correlate with clinicopathological factors. Conclusion: Expression of miRNA 146a/b, 221, and 222 was increased by BRAF