Upregulated miR-222 has been observed in prostate cancer (38), primary glioblastoma (39), papillary thyroid carcinoma (19) and breast cancer (40), and a possible functional role has been proposed for miR-222 in cell growth and proliferation due to its effect on the expression of cell cycle regulatory proteins, including the cyclin-dependent kinase inhibitor p27Kip1 (40–42). This evidence concerns the gene CDKN3 and differentiated thyroid carcinoma.